prof.dr.ir. L. Abelmann
Bioelectronics (BE), Department of Microelectronics
Expertise: Magnetism, Nanotechnology, MEMS
Themes: Bioinspired electronics, Neuroprosthetics, - stimulation and -modulationCircuit theory course for first year EE students, Part 1 Build, analyze and characterize a sound system consisting of a power source, amplifier and 3-way filters BSc 2nd year project Minor Linear electrical circuits and components, non-linear active components in both the analog and the digital domain BioMEMS, biosensors, bioelectronics, ultrasound, microfluidics, wavefield imaging in monitoring, diagnosis and treatment (not running) "Classical and Quantum Mechanics" (EE1P11) teaches the basic elements of physics that are required to become an electrical engineer.EE1C1 Linear Circuits A
EE1L1 IP1: Booming Bass
EE2G1 Electrical Engineering for the Next Generation
ET-Mi-201 Electronics for Robotics
ET3033TU Circuit analysis
ET4127 Themes in biomedical electronics
Education history
EE1P11 Classical and Quantum Mechanics
Abelmann, Leon; Gwag, Eunheui; Sung, Baeckkyoung;
Journal of Magnetism and Magnetic Materials,
Volume 591, 2024. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2023.171696
Keywords: ...
3D printing; Cell culture; Cells; Hematite; Nanomagnetics; Cylindrical magnets; Force density; Halbach array; Hepg4; Magnet systems; Magnetic force; Micromod; Optimized designs; Soft magnetics; Uniform force; Permanent magnets.
Abstract: ...
We optimized designs of permanent magnet systems to study the effect of magnetic nanoparticles on cell cultures in microslide channels. This produced two designs, one of which is based on a large cylindrical magnet that applies a uniform force density of 6 MN/m3 on soft magnetic iron-oxide spherical nanoparticles at a field strength of over 300 mT. We achieved a force uniformity of better than 14 % over the channel area, leading to a concentration variation that was below our measurement resolution. The second design was aimed at maximizing the force by using a Halbach array. We indeed increased the force by more than one order of magnitude at force density values over 400 MN/m3, but at the cost of uniformity. However, the latter system can be used to trap magnetic nanoparticles efficiently and to create concentration gradients. We demonstrated both designs by analyzing the effect of magnetic forces on the cell viability of human hepatoma Hep G2 cells in the presence of bare Fe2O3 and cross-linked dextran iron-oxide cluster-type particles (MicroMod). Python scripts for magnetic force calculations and particle trajectory modeling as well as source files for 3D prints have been made available so these designs can be easily adapted and optimized for other geometries. © 2023
document
Nguyen, Ngoc Quang; Jeong, Younhee; Abelmann, Leon; Ryu, Jungju; Sohn, Daewon;
Colloids and Surfaces A: Physicochemical and Engineering Aspects,
Volume 680, 2024. All Open Access, Green Open Access. DOI: 10.1016/j.colsurfa.2023.132631
Keywords: ...
Kaolinite; Raman spectroscopy; Ultraviolet visible spectroscopy; Wastewater treatment; halloysite nanotube; Dye absorption; Dye removal; Dyes adsorptions; Eco-friendly; Halloysite; Halloysite nanotubes; Magnetic particle; pH condition; Structures and properties; Sunset yellows; absorption; Article; chemical structure; controlled study; energy dispersive X ray spectroscopy; Fourier transform infrared spectroscopy; pH; Raman spectrometry; scanning electron microscopy; transmission electron microscopy; ultraviolet visible spectroscopy; waste component removal; waste water management; X ray diffraction; X ray photoemission spectroscopy; zeta potential; Nanotubes.
Abstract: ...
Halloysite nanotubes (HNTs) have been extensively investigated for potential utilization due to their unique structure and properties as a type of natural, eco-friendly clay. The synthesis and modification of magnetic halloysite nanotubes was studied using several experimental techniques including SEM, TEM, FT-IR, Raman spectroscopy, UV-Vis spectroscopy, and BET. Dye absorption experiments were conducted to understand bonding using EDS, XPS, XRD, and Raman spectroscopy. In this study, we evaluated Sunset Yellow FCF (SY) dye removal as a model to understand bonding structures among magnetic HNTs, magnetic particles, and dye molecules. We focus on the interactions of SY-magnetic HNTs and characteristics of magnetization by VSM after SY dye adsorption, which highlight the notable features of magnetic halloysite nanotubes. We used different pH environments to study the behavior of magnetic HNTs after dye absorption. The application of these modified HNTs is promising for future organic dye removal and wastewater treatment. © 2023 Elsevier B.V.
document
Manikandan, Aiswarya Lakshmi; Gurboga, Berfin; Munzenrieder, Niko; Raman, Akash; Gardeniers, Han J. G. E.; Susarrey-Arce, Arturo; Abelmann, Leon; Khalil, Islam S. M.;
conference, 2024. DOI: 10.1109/BioRob60516.2024.10719906
Keywords: ...
Activation energy; Breath controlled devices; Hydrogen fuels; Intelligent robots; Medical robotics; Active area; Active electrodes; Cell-be; Cell/B.E; Cell/BE; Electrode areas; On-board batteries; Power; Proton exchange membranes; Small scale; Redox reactions.
Abstract: ...
Magnetically guided untethered devices are used in a variety of medical applications. These devices are typically powered by onboard battery units. Hydrogen fuel cells (FC) are a promising alternative power source for such small-scale devices since they rely on a sustainable fuels which produce electric power from the redox reaction of hydrogen and oxygen across a proton exchange membrane (PEM). Understanding the impact of decreasing the active electrode area in FCs is crucial for deploying FCs in untethered devices and gaining insights into the challenges of downscaling the devices. This paper investigates the performance of PEM FCs (PEMFCs) when their active area is reduced, and when the FC is supplied with reactants at different flow rates from a PEM electrolyzer. PEMFCs with three active electrode areas, 3.5 × 3.5 cm2, 2.7×2.7 cm2, and 1.6×1.6 cm2were designed, fabricated, and characterised. Maximum fuel cell output powers of 0.3 W, 0.09 W, and 0.03 W (maximum power densities of 0.025 W/cm2, 0.012 W/cm2, and 0.013 W/cm2) corresponding to the three aforementioned areas were achieved. Mathematical modeling of the PEMFC simulated the FC response, providing insights into the activation kinetics of the fuel cell. The smallest PEMFC with an active area of 1.6 × 1.6 cm2was used to power an inductor coil (rated 130 mA, 150 mH, 8 Ω). This study can guide the development of FCs to power untethered devices. © 2024 IEEE.
document
Soyarslan, Celal; Havinga, Jos; Abelmann, Leon; van den Boogaard, Ton;
Results in Physics,
Volume 44, 2023. All Open Access, Gold Open Access, Green Open Access. DOI: 10.1016/j.rinp.2022.106188
Abstract: ...
We present a computational framework for two-scale asymptotic homogenization to determine the intrinsic magnetic permeability of composites. To this end, considering linear magnetostatics, both vector and scalar potential formulations are used. Our homogenization algorithm for solving the cell problem is based on the displacement method presented in Lukkassen et al. 1995, Composites Engineering, 5(5), 519-531. We propose the use of the meridional eccentricity of the permeability tensor ellipsoid as an anisotropy index quantifying the degree of directionality in the linear magnetic response. As application problems, 2D regular and random microstructures with overlapping and nonoverlapping monodisperse disks, all of which are periodic, are considered. We show that, for the vanishing corrector function, the derived effective magnetic permeability tensor gives the (lower) Reuss and (upper) Voigt bounds with the vector and scalar potential formulations, respectively. Our results with periodic boundary conditions show an excellent agreement with analytical solutions for regular composites, whereas, for random heterogeneous materials, their convergence with volume element size is fast. Predictions for material systems with monodisperse overlapping disks for a given inclusion volume fraction provide the highest magnetic permeability with the most increased inclusion interaction. In contrast, the disk arrangements in regular square lattices result in the lowest magnetic permeability and inadequate inclusion interaction. Such differences are beyond the reach of the isotropic effective medium theories, which use only the phase volume fraction and shape as mere statistical microstructural descriptors. © 2023 The Authors
document
Richter, Michiel; Kaya, Mert; Sikorski, Jakub; Abelmann, Leon; Kalpathy Venkiteswaran, Venkatasubramanian; Misra, Sarthak;
Soft Robotics,
Volume 10, Issue 3, pp. 647 – 659, 2023. All Open Access, Green Open Access. DOI: 10.1089/soro.2022.0031
Keywords: ...
Magnetic Fields; Magnetics; Magnets; Phantoms, Imaging; Dipole moment; Economic and social effects; Functional polymers; Magnetic fields; Magnetic moments; Medical applications; Permanent magnets; Continuum robot; Cosserat rod; Dipole interaction; Direct contact; External magnetic field; Flexibility; Flexible magnetics; Local dipole interaction; Magnetic continuum manipulator; Manipulator designs; magnetic field; magnetism; Manipulators.
Abstract: ...
Magnetic continuum manipulators (MCMs) are a class of continuum robots that can be actuated without direct contact by an external magnetic field. MCMs operating in confined workspaces, such as those targeting medical applications, require flexible magnetic structures that contain combinations of magnetic components and polymers to navigate long and tortuous paths. In cylindrical MCM designs, a significant trade-off exists between magnetic moment and bending flexibility as the ratio between length and diameter decreases. In this study, we propose a new MCM design framework that enables increasing diameter without compromising on flexibility and magnetic moment. Magnetic soft composite helices constitute bending regions of the MCM and are separated by permanent ring magnets. Local dipole interactions between the permanent magnets can reduce bending stiffness, depending on their size and spacing. For the particular segment geometry presented herein, the local dipole interactions result in a 31% increase in angular deflection of composite helices inside an external magnetic field, compared to helices without local interactions. In addition, we demonstrate fabrication, maneuverability, and example applications of a multisegment MCM in a phantom of the abdominal aorta, such as passing contrast dye and guidewires. © Copyright 2023, Mary Ann Liebert, Inc., publishers 2023.
document
Singh, Sukhvinder; Abelmann, Leon; Gao, Haibin; Hartmann, Uwe;
Journal of Magnetism and Magnetic Materials,
Volume 586, 2023. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2023.171138
Keywords: ...
Film preparation; Iron alloys; Magnetic force microscopy; Magnetic thin films; Nickel alloys; Argon pressure; Domain configurations; Increase in pressure; Magnetic-force microscopy; Permalloy films; Permalloy thin films; Permalloys; Pressure domain; Sputter pressure; Sputtering; Magnetic domains.
Abstract: ...
Well-defined and technically relevant domain configurations are sought in patterned magnetic thin films. We used Magnetic Force Microscopy to investigate these in square-patterned Permalloy films. The films were prepared using dc sputter deposition by varying the Argon pressure from 1.5×10−3 to 30.0×10−3 mbar. The Landau domain configuration was found in films prepared at 1.5×10−3 mbar pressure. With an increase in pressure, tulip and irregular domains were consecutively formed. Based on magnetic and structural characterizations, an increase in coercivity and a decrease in Permalloy film density were observed at the same time. © 2023 Elsevier B.V.
document
Magdanz, Veronika; Cumming, Jack R.; Salamzadeh, Sadaf; Tesselaar, Sven; Alic, Lejla; Abelmann, Leon; Khalil, Islam S. M.;
conference, 2023. All Open Access, Green Open Access. DOI: 10.1109/IROS55552.2023.10341258
Keywords: ...
Cells; Chemical activation; Cytology; Magnetic materials; Magnetometers; Nanomagnetics; Nanoparticles; Bio-hybrids; Detection coils; Electrostatic attractions; Faraday Law; Localisation; Magnetic excitations; Micro robots; Nanoparticle coatings; Pulse echoes; Sperm cells; Magnetometry.
Abstract: ...
Magnetic nanoparticles can be electrostatically assembled around sperm cells to form biohybrid microrobots. These biohybrid microrobots possess sufficient magnetic material to potentially allow for pulse-echo localization and wireless actuation. Alternatively, magnetic excitation of these nanoparticles can be used for localization based on Faraday's law of induction using a detection coil. Here, we investigate the influence of the electrostatic attraction between positively charged nanoparticles and negatively charged sperm cells on the activation of the nanoparticles during nonlinear differential magnetometry and wireless magnetic actuation. Activation of clusters of free nanoparticles and nanoparticles bound to the body of sperm cells is achieved by a combination of a high- frequency alternating field and a pulsating static field. The nonlinear response in both cases indicates that constraining the nanoparticles is likely to yield significant decreases in the magnetometry sensitivity. While the attachment of particles to the cells enables wireless actuation (rolling locomotion), the rate of change of the magnetization of the nanoparticles decreases one order of magnitude compared to free nanoparticles. © 2023 IEEE.
document
Welleweerd, Marcel K.; Hageman, Tijmen; Pichel, Marc; Van As, Dave; Keizer, Hans; Hendrix, Jordi; Micheal, Mina M.; Khalil, Islam S. M.; Mir, Alveena; Korkmaz, Nuriye; Kr{\"a}winkel, Robbert; Chevrier, Daniel M.; Faivre, Damien; Fernandez-Castane, Alfred; Pfeiffer, Daniel; Abelmann, Leon;
Review of Scientific Instruments,
Volume 93, Issue 9, 2022. All Open Access, Green Open Access. DOI: 10.1063/5.0098008
Keywords: ...
Magnetic Fields; Magnetics; Magnets; Spectrophotometry; Suspensions; 3D printers; Bacteria; Cost effectiveness; Density measurement (optical); Magnetism; Meteorological instruments; Open source software; Spectrophotometers; Suspensions (fluids); 3d prints; Board layout; Circuit boards; Density meter; Design circuits; Electronic design; Magnetic cells; Magnetic particle; Magnetotactic Bacteria; Open-source; magnet; magnetic field; magnetism; procedures; spectrophotometry; suspension; Density (optical).
Abstract: ...
We present a spectrophotometer (optical density meter) combined with electromagnets dedicated to the analysis of suspensions of magnetotactic bacteria. The instrument can also be applied to suspensions of other magnetic cells and magnetic particles. We have ensured that our system, called MagOD, can be easily reproduced by providing the source of the 3D prints for the housing, electronic designs, circuit board layouts, and microcontroller software. We compare the performance of our system to existing adapted commercial spectrophotometers. In addition, we demonstrate its use by analyzing the absorbance of magnetotactic bacteria as a function of their orientation with respect to the light path and their speed of reorientation after the field has been rotated by 90°. We continuously monitored the development of a culture of magnetotactic bacteria over a period of 5 days and measured the development of their velocity distribution over a period of one hour. Even though this dedicated spectrophotometer is relatively simple to construct and cost-effective, a range of magnetic field-dependent parameters can be extracted from suspensions of magnetotactic bacteria. Therefore, this instrument will help the magnetotactic research community to understand and apply this intriguing micro-organism. © 2022 Author(s).
document
Klein, Yannick P.; Abelmann, Leon; Gardeniers, Han;
Journal of Magnetism and Magnetic Materials,
Volume 555, 2022. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.1016/j.jmmm.2022.169371
Keywords: ...
Magnetic fields; Magnetic fluids; Magnetic resonance; Saturation magnetization; Field homogeneity; Halbach; Halbach magnets; Homogeneous magnetic field; Inhomogeneities; Magnetic field profile; Magnetic-field; Microliters; Micromagnets; Permanent magnet assemblies; Permanent magnets.
Abstract: ...
A novel principle of passive magnetic field shimming for permanent magnet assemblies is introduced, based on defined amounts of a ferrofluid suspension contained in a microliter volume plastic container that is accurately positioned within the magnet bore. The ferrofluid volume acts as a micromagnet that compensates inhomogeneities in the magnetic field profile. A proof of principle is shown for a permanent magnet assembly, derived from a Halbach design, with two additional movable rings of magnets. These rings result in an average magnetic field strength of 1.06 T inside the bore, 19 % higher than the Halbach alone. Two options for field shimming with ferrofluids are shown: changing the material volume or choosing a ferrofluid with different saturation magnetization value. With the tested simple single-cube ferrofluid implementation the field homogeneity is improved from 86 ppm to 8 ppm over a sampling length of 5.5 mm. Better homogeneity is expected with more sophisticated ferrofluid arrangements. The complete assembly has a size of 5 × 5 × 4.2 cm3 and a weight of 332 g. The demonstrated concept is particularly attractive for mobile magnetic resonance systems, as it does not require electrical power during operation. © 2022 The Authors
document
Magdanz, Veronika; Klingner, Anke; Abelmann, Leon; Khalil, Islam S. M.;
Journal of Micro-Bio Robotics,
Volume 18, Issue 1-2, pp. 49 – 60, 2022. All Open Access, Green Open Access. DOI: 10.1007/s12213-023-00158-5
Keywords: ...
Cytology; Electrostatics; Iron; Nanomagnetics; Reynolds number; Rigid structures; Self assembly; Stiffness; Bending stiffness; Bending wave; Bio-hybrids; Electrostatic self-assembly; Magnetic; Membrane potentials; Micro robots; Sperm cells; Swimming speed; Transverse bending; Cells.
Abstract: ...
Cell membrane potential affects the electrostatic self-assembly of magnetizable nanoparticles around the flagellum of sperm cells, leading to the formation of biohybrid microrobots (i.e., IRONSperm) with various bending stiffness. Here we explain the influence of bull sperm cell membrane potential on the formation of two types of IRONSperm samples that are produced by electrostatic self-assembly. The first type is a proximal-coated soft body with nanoparticles concentrated on the head to maintain high flexibility of the flagellum and create a passively propagating transverse bending wave under the influence of an external rotating magnetic field. The second type is a rigid-body with nanoparticles approximately uniformly distributed along the length to provide arbitrary geometry that maintains a constant chiral shape and propel by rotation about its long axis. We present a magneto-elastohydrodynamic model to predict the swimming speed at low Reynolds number for rigid IRONSperm with arbitrary shapes, and show that decreasing the bending stiffness allows the model to capture the behavior of its soft counterpart. While the response of a rigid chiral IRONSperm is distinguished by a greater swimming speed with a smooth decay with frequency, the benefit of a soft flagellum in certain scenarios would present a much smaller range of frequencies for wireless actuation. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
document
Middelhoek, Kaz I. N. A.; Magdanz, Veronika; Abelmann, Leon; Khalil, Islam S. M.;
Biomedical Materials (Bristol),
Volume 17, Issue 6, 2022. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.1088/1748-605X/ac8b4b
Keywords: ...
Cells; Controlled drug delivery; Cytology; Magnetohydrodynamics; Remote control; Targeted drug delivery; Ultrasonic imaging; doxorubicin; ferromagnetic material; iron nanoparticle; iron oxide nanoparticle; self assembled nanomaterial; Bio-hybrids; Cell delivery; Clusters model; In-vivo; Magnetic actuation; Micro robots; Microrobot aggregation; Rotating magnetic fields; Sperm; Ultrasound imaging; animal cell; Article; cell viability; controlled study; cytotoxicity; drug delivery system; echography; female; human; human cell; in vivo study; magnetic field; magnetism; magneto hydrodynamic model; male; nanopharmaceutics; nonhuman; particle size; sperm; spermatozoon; static electricity; statistical model; ultrasound; viscosity; Aspect ratio.
Abstract: ...
Individual biohybrid microrobots have the potential to perform biomedical in vivo tasks such as remote-controlled drug and cell delivery and minimally invasive surgery. This work demonstrates the formation of biohybrid sperm-templated clusters under the influence of an external magnetic field and essential functionalities for wireless actuation and drug delivery. Ferromagnetic nanoparticles are electrostatically assembled around dead sperm cells, and the resulting nanoparticle-coated cells are magnetically assembled into three-dimensional biohybrid clusters. The aim of this clustering is threefold: First, to enable rolling locomotion on a nearby solid boundary using a rotating magnetic field; second, to allow for noninvasive localization; third, to load the cells inside the cluster with drugs for targeted therapy. A magneto-hydrodynamic model captures the rotational response of the clusters in a viscous fluid, and predicts an upper bound for their step-out frequency, which is independent of their volume or aspect ratio. Below the step-out frequency, the rolling velocity of the clusters increases nonlinearly with their perimeter and actuation frequency. During rolling locomotion, the clusters are localized using ultrasound images at a relatively large distance, which makes these biohybrid clusters promising for deep-tissue applications. Finally, we show that the estimated drug load scales with the number of cells in the cluster and can be retained for more than 10 h. The aggregation of microrobots enables them to collectively roll in a predictable way in response to an external rotating magnetic field, and enhances ultrasound detectability and drug loading capacity compared to the individual microrobots. The favorable features of biohybrid microrobot clusters place emphasis on the importance of the investigation and development of collective microrobots and their potential for in vivo applications. © 2022 The Author(s). Published by IOP Publishing Ltd.
document
Schouten, Martijn; Abelmann, Leon; Krijnen, Gijs;
Additive Manufacturing,
Volume 56, 2022. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.1016/j.addma.2022.102890
Keywords: ...
Calibration; Extrusion; Fabrication; Image processing; Inductive sensors; Optical data processing; Printing presses; 3-D printing; 3D-printing; Calibration method; Calibration procedure; Detection coils; Fused filament fabrication; Inductive method; Metallics; Multi materials; Optical-; 3D printers.
Abstract: ...
In this work an optical and inductive calibration procedures for calibrating multi-material fused filament fabrication 3D printers in the x and y directions is presented. The inductive calibration is based on the principle that the inductance of a detection coil placed on the print bed changes when the (metallic) extrusion nozzle passes it. This calibration method shows a repeatability of up to 2µm. To determine the accuracy of this calibration method, another calibration method is proposed that directly measures the position of the deposited material. During this alternative process, a calibration structure is printed on an A4-format sheet of paper using every tool. The paper is subsequently scanned using a digital scanner, and the resulting image is analyzed using an image-processing script. Using this method as a reference, it was determined that the inductive method has an accuracy of approximately 45µm. For applications where this accuracy is sufficient, the inductive method provides a fast solution that requires little to no user interaction. For more demanding applications, the optical calibration might be the better choice, since it is more time-consuming but yields a more accurate solution. It is expected that the accurate calibration of tool offsets will reduce both the chance of poor adhesion between materials and the mixing of filaments due to local over- and under-extrusion at material interfaces. © 2022 The Author(s)
document
Soyarslan, Celal; Havinga, Jos; Abelmann, Leon; van den Boogaard, Ton;
Key Engineering Materials,
Volume 926 KEM, pp. 2040 – 2049, 2022. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.4028/p-3no5jw
Abstract: ...
We investigate the predictive performance of specific analytical and numerical methods to determine the effective magnetic properties of two-phase steels at the macroscale. We utilize various mixture rules reported in the literature for the former, some of which correspond to rigorous bounds, e.g., Voigt (arithmetic) and Reuss (harmonic) averages. For the latter, we employ asymptotic homogenization together with the finite element method (FEM) and periodic boundary conditions (PBC). The voxel-based discretization of the representative volume element is conducted with digital image processing on the existing micrographs of DP600-grade steel. We show that unlike the considered isotropic mixture rules, which use only the phase volume fraction as the statistical microstructural descriptor, finite element method-based first-order asymptotic homogenization allows prediction of both phase content and directional dependence in the magnetic permeability by permitting an accurate consideration of the underlying phase geometry. © 2022 The Author(s). Published by Trans Tech Publications Ltd, Switzerland.
document
Van Renselaar, Erwin; Keitel, Benedikt; Dinc, Mehmet; Mizaikoff, Boris; Susarrey-Arce, Arturo; Gardeniers, Han J. G. E.; Abelmann, Leon; Khalil, Islam S. M.;
conference, 2022. All Open Access, Green Open Access. DOI: 10.1109/MARSS55884.2022.9870509
Keywords: ...
Drug delivery; MEMS; Battery pack; Localised; Material removal; Micro robots; Miniature devices; Power; Power densities; Power electronic devices; Scaling rules; Various functions; Reynolds number.
Abstract: ...
There is an increasing need for wireless autonomous micro electromechanical systems (MEMS) and microrobots that can perform various functions such as sensing, diagnosis, locomotion, actuation, implantation, material removal, manipulation, and localized drug delivery. A major problem with these systems is the production, storage, and transduction of power at the micro scale. In addition, these miniature devices cannot use existing battery packs that are commonly used to power electronic devices. These MEMS and microrobots need on-board power sources that are miniaturized to their size. Together with the energy of an external source, some basic functions of microrobots can be powered simultaneously. This study seeks to develop a theoretical framework based on a chemo-electromagnetic model for use in the design of microrobots with full energetic autonomy. We first conceive a microrobot design and derive its mathematical model; the design consists of an on-board fuel generator, electrochemical device, electromagnetic device, and a locomotion mechanism. Then we present numerical simulations to show the relationship between the consumption rate of the H2 source, power density, and angular and translational velocities at low Reynolds number. We find that power density decreases approximately linearly with the diameter, while the relative velocity with respect to the body-length is approximately inversely proportional to the size, making downscaling favourable for this class of untethered devices. © 2022 IEEE.
document
Magdanz, Veronika; Klingner, Anke; Abelmann, Leon; Khalil, Islam S. M.;
conference, 2022. All Open Access, Green Open Access. DOI: 10.1109/MARSS55884.2022.9870506
Keywords: ...
Cytology; Electrostatics; MEMS; Nanomagnetics; Nanoparticles; Reynolds number; Rigid structures; Self assembly; Stiffness; Bending stiffness; Bending wave; Bio-hybrids; Electrostatic self-assembly; Functionalized; Membrane potentials; Rigid body rotation; Sperm cells; Swimming speed; Transverse bending; Cells.
Abstract: ...
Cell membrane potential affects the electrostatic self-assembly of magnetizable nanoparticles around the flagellum of sperm cells, leading to the formation of biohybrid microrobots (i.e. IRONSperm) with various bending stiffness. Here we explain the influence of bull sperm cell membrane potential on the formation of two types of IRONSperm samples that are produced by electrostatic self-assembly. The first is a proximal-coated soft body with nanoparticles concentrated on the head to maintain high flexibility of the flagellum and create a passively propagating transverse bending wave under the influence of an external rotating magnetic field. The second is a rigid-body with nanoparticles approximately uniformly distributed along the length to provide arbitrary geometry that maintains a constant chiral shape and propel by rotation about its long axis. We present a magneto-elastohydrodynamic model to predict the swimming speed at low Reynolds number for rigid IRONSperm with arbitrary shapes, and show that decreasing the bending stiffness allows the model to capture the behavior of its soft counterpart. While the response of a rigid chiral IRONSperm is distinguished by a greater swimming speed with a smooth decay with frequency, the benefit of a soft flagellum in certain scenarios would present a much smaller range of frequencies for wireless actuation. © 2022 IEEE.
document
Groenhuis, Vincent; Rolff, Gijs; Bosman, Koen; Abelmann, Leon; Stramigioli, Stefano;
conference, 2022. All Open Access, Green Open Access. DOI: 10.1109/IROS47612.2022.9981190
Keywords: ...
Calibration; Stepping motors; Systematic errors; Absolute position; Calibration techniques; Coil current; Position detection; Sensorless; Shock resistance; Smoothing techniques; Space efficiencies; Stepper motor; Stochastic measurement; Stochastic systems.
Abstract: ...
Absolute position detection in sensorless electric stepper motors potentially allows for higher space efficiency, improved shock resistance, simplified installation, reduced number of parts and lowered cost. A prototype is demonstrated measuring 42 × 42 × 34 mm3 with seven coils arranged in a star configuration. The rotor is φ 25.8 × 12.5 mm2 and has 51 teeth which are irregularly spaced. At the driver side, the coil currents are measured during motion in order to reconstruct the absolute position of the motor. Calibration and smoothing techniques are used to reduce systematic and stochastic measurement errors, respectively. The motor is able to detect and correct its position after externally-induced stalls at the tested motor speeds from 40 rpm to 108 rpm. The holding torque is 0.23 N m at an armature current of 1 A; on average the torque is 7% lower than that of a reference bipolar stepper motor with the same dimensions. The results show that dynamic position sensing and correction are possible for a range of velocities, but not at standstill. The driver requires seven current sensors and sufficient computational power, and proper calibration of motor intrinsics is required beforehand. The presented technology could make existing 3-D printers and other machines with open-loop stepper motors more robust and increase the range of operating speeds and accelerations, without the adverse side-effects of increased complexity and cost associated with dedicated position sensors. © 2022 IEEE.
document
Song, Suk-Heung; Yoon, Jinsik; Jeong, Yongkyo; Jung, Yong-Gyun; Abelmann, Leon; Park, Wook;
Journal of Magnetism and Magnetic Materials,
Volume 539, 2021. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2021.168341
Keywords: ...
Automation; Dispensers; Glass; Magnetic bubbles; Suspensions (components); Automatic dispenser; Glass-coated particle; Low-costs; Magnetic metals; Magnetic particle; Mass production process; Metal core; Particle arrays; Rod-shape particle; Rod-shaped; Self assembly.
Abstract: ...
We develop a low-cost, mass-production process for creating rod-shaped glass-coated magnetic particles consisting of a magnetic metal core and glass shell structure. We investigate their magnetic properties by analyzing their optical absorbance in suspension as a function of the orientation of a 1 mT magnetic field. From the response we derive that the magnetization of the particles is 0.1 MA/m. We demonstrate an automated system that quantifies and dispenses a large amount of RGMPs by magnetic self-assembly on a high-volume plate patterned with an array of holes. This automatic dispenser can provide packaging forms with the smallest unit of RGMPs for in-vitro diagnostics and is expected to reduce the time and effort required for the assembly and packaging process. © 2021 Elsevier B.V.
document
Klein, Y. P.; Abelmann, L.; Gardeniers, J. G. E.;
IEEE Transactions on Magnetics,
Volume 57, Issue 7, 2021. All Open Access, Green Open Access. DOI: 10.1109/TMAG.2021.3077301
Keywords: ...
Magnetic fields; Magnetization; Monte Carlo methods; Permanent magnets; Sensitivity analysis; Active shimming; Different sizes; Field homogeneity; General designs; Magnet assembly; Magnet configurations; Magnetic field homogeneity; Positioning error; Nuclear magnetic resonance.
Abstract: ...
We optimized the magnetic field homogeneity of two canonical designs for mobile microfluidic nuclear magnetic resonance (NMR) applications: two parallel magnets with an air gap and a modified Halbach array. Along with the influence of the sample length, general design guidelines will be presented. For a fair comparison, the sensitive length of the sample has been chosen to be the same as the gap size between the magnets to ensure enough space for the transmitting and receiving unit, as well as basic electric shimming components. Keeping the compactness of the final device in mind, a box with an edge length 5 times the gap size has been defined, in which the complete magnet configuration should fit. With the chosen boundary conditions, the simple parallel cuboid configuration reaches the best homogeneity without active shimming ( 0.5 B s, 41 ppm), while the pseudo-Halbach configuration has the highest field strength ( 0.9 B s , 994 ppm), assuming perfect magnets. However, permanent magnet configurations suffer from imperfections, such as magnetization, fabrication, and positioning errors, which results in worse magnetic field homogeneities than expected from simulations using a fixed optimized parameter set. We present a sensitivity analysis for a magnetic cube and the results of studies of the variations in the magnetization and angle of magnetization of magnets purchased from different suppliers, composed of different materials and coatings, and of different sizes. We performed a detailed Monte Carlo simulation on the effect of the measured distribution of magnetic properties on the mentioned configurations. The cuboid design shows a mean homogeneity of 430 ppm (std. dev. 350 ppm), the Pseudo-Halbach has a mean homogeneity of 1086 ppm (std dev. 8 ppm). © 1965-2012 IEEE.
document
Sung, Baeckkyoung; Abelmann, Leon;
Data in Brief,
Volume 34, 2021. All Open Access, Gold Open Access, Green Open Access. DOI: 10.1016/j.dib.2021.106716
Abstract: ...
This dataset shows the agglomerate dimension and structure of oleic acid-coated superparamagnetic nanoparticles (SPIONs), which are dispersed in the nematic fluid of a thermotropic liquid crystal (LC), 4-cyano-4′-pentylbiphenyl (5CB). The analysed datasets were acquired from the raw images of the SPION-5CB mixtures obtained using cryogenic transmission electron microscopy (cryo-TEM) and polarised optical microscopy. The image data were quantitatively analysed to extract statistical information on the sizes of SPIONs and their agglomerates and the inter-particle spacing of the agglomerated SPIONs. This dataset supports the fundamental understanding on how colloidal nanospheres behave in an anisotropic fluid, and has a potential to be used as a part of database for automated design of new hybrid materials. © 2021 The Author(s)
document
Groenhuis, Vincent; Rolff, Gijs; Bosman, Koen; Abelmann, Leon; Stramigioli, Stefano;
IEEE Robotics and Automation Letters,
Volume 6, Issue 4, pp. 7201 – 7208, 2021. All Open Access, Green Open Access. DOI: 10.1109/LRA.2021.3097077
Keywords: ...
Agricultural robots; Degrees of freedom (mechanics); Compact solutions; Mechanical design; Mechanical systems; Multiple degrees of freedom; Multiple joints; Multiple rotors; Revolutions per minutes; Robotic systems; Stepping motors.
Abstract: ...
Multi-axis stepper motors offer a compact solution to actuate multiple degrees of freedom in a mechanical system by a single device. This research presents an electric stepper motor with three coaxial shafts driven by a single stator. The motor dimensions are 42 × 42 × 44 mm3 (excluding output shafts), its mass is 0.326 kg and it includes three rotors of height 7 mm and different number of teeth. The maximum torque for one rotor at low speed and 1 A current is 0.10 N m, which is comparable to that of a conventional stepper motor with similar rotor size. When multiple rotors are driven simultaneously, then the total power has to be distributed over the three rotors, resulting in 42% lower torque on average. The maximum no-load speed is 4000 revolutions per minute. The coaxial output shaft configuration poses significant challenges but also unique opportunities in actuating multiple joints of a robotic system. In many applications, the mechanical design can be redesigned to make effective use of the multi-motor design. An example of a three-DOF robot arm is demonstrated that can be efficiently driven by the proposed motor. © 2016 IEEE.
document
Stevens, Michiel; Liu, Peng; Niessink, Tom; Mentink, Anouk; Abelmann, Leon; Terstappen, Leon;
Diagnostics,
Volume 11, Issue 6, 2021. All Open Access, Gold Open Access, Green Open Access. DOI: 10.3390/diagnostics11061020
Keywords: ...
epithelial cell adhesion molecule; ferrofluid; antigen expression; Article; cell separation; cellular distribution; circulating tumor cell; comparative study; controlled study; enrichment culture; finite element analysis; flow rate; human; human cell; immunomagnetic separation; male; measurement; prediction.
Abstract: ...
Due to the low frequency of circulating tumor cells (CTC), the standard CellSearch method of enumeration and isolation using a single tube of blood is insufficient to measure treatment effects consistently, or to steer personalized therapy. Using diagnostic leukapheresis this sample size can be increased; however, this also calls for a suitable new method to process larger sample inputs. In order to achieve this, we have optimized the immunomagnetic enrichment process using a flow-through magnetophoretic system. An overview of the major forces involved in magnetophoretic separation is provided and the model used for optimizing the magnetic configuration in flow through immunomagnetic enrichment is presented. The optimal Halbach array element size was calculated and both optimal and non-optimal arrays were built and tested using anti-EpCAM ferrofluid in combination with cell lines of varying EpCAM antigen expression. Experimentally measured distributions of the magnetic moment of the cell lines used for comparison were combined with predicted recoveries and fit to the experimental data. Resulting predictions agree with measured data within measurement uncertainty. The presented method can be used not only to optimize magnetophoretic separation using a variety of flow configurations but could also be adapted to optimize other (static) magnetic separation techniques. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
document
Sung, Baeckkyoung; Kim, Min-Ho; Abelmann, Leon;
Bioengineering and Translational Medicine,
Volume 6, Issue 1, 2021. All Open Access, Gold Open Access, Green Open Access. DOI: 10.1002/btm2.10190
Keywords: ...
Gels; Gene therapy; Hybrid materials; Hydrogels; Magnetism; Medical applications; Nanostructured materials; Physicochemical properties; Structural design; catalase; chitosan; collagen; diclofenac; doxorubicin; fluorouracil; gadolinium; graphene; graphene oxide; hyaluronic acid; hydrogel; macrogol; magnetic microgel; magnetic nanoparticle; methotrexate; microgel (material); nanocomposite; nanogel; nanomaterial; nanoparticle; polymer; polyvinyl alcohol; reactive oxygen metabolite; superoxide dismutase; unclassified drug; Anticancer treatment; Biological environments; Biomedical applications; Engineering principles; Inorganic nanoparticle; Micro and nanostructures; Multifunctional composites; Physico-chemical mechanisms; biocatalysis; biodegradability; biomanipulation; biomedicine; bioseparation; cancer chemotherapy; cancer gene therapy; cancer therapy; crystal structure; decellularization; drug delivery system; drug diffusion; electrospinning; encapsulation; entropy; enzyme immobilization; exosome; fluorescence microscopy; gene therapy; hydrogen bond; hydrophobicity; hysteresis; magnetic field; microfluidics; nanofabrication; nanomedicine; personalized medicine; photodynamic therapy; photoluminescence; photothermal therapy; polymerization; regenerative medicine; Review; tissue engineering; tissue regeneration; Magnetic nanoparticles.
Abstract: ...
Soft micro- and nanostructures have been extensively developed for biomedical applications. The main focus has been on multifunctional composite materials that combine the advantages of hydrogels and colloidal particles. Magnetic microgels and nanogels can be realized by hybridizing stimuli-sensitive gels and magnetic nanoparticles. They are of particular interest since they can be controlled in a wide range of biological environments by using magnetic fields. In this review, we elucidate physical principles underlying the design of magnetic microgels and nanogels for biomedical applications. Particularly, this article provides a comprehensive and conceptual overview on the correlative structural design and physical functionality of the magnetic gel systems under the concept of colloidal biodevices. To this end, we begin with an overview of physicochemical mechanisms related to stimuli-responsive hydrogels and transport phenomena and summarize the magnetic properties of inorganic nanoparticles. On the basis of the engineering principles, we categorize and summarize recent advances in magnetic hybrid microgels and nanogels, with emphasis on the biomedical applications of these materials. Potential applications of these hybrid microgels and nanogels in anticancer treatment, protein therapeutics, gene therapy, bioseparation, biocatalysis, and regenerative medicine are highlighted. Finally, current challenges and future opportunities in the design of smart colloidal biodevices are discussed. © 2020 The Authors. Bioengineering & Translational Medicine published by Wiley Periodicals LLC on behalf of American Institute of Chemical Engineers.
document
O'Connor, Jonathan S.; Kim, Heesoo; Gwag, Eunheui; Abelmann, Leon; Sung, Baeckkyoung; Manz, Andreas;
conference, 2021. All Open Access, Green Open Access. DOI: 10.1109/MEMS51782.2021.9375385
Keywords: ...
Cell culture; Cooling systems; Drops; Gels; MEMS; Surface active agents; Channel temperature; Gelatin microgels; HepG2 cell line; High throughput; Human liver cells; Micro-fluidic devices; Rectangular channel; Surfactant-free; 3D printers.
Abstract: ...
In this work, we describe the rapid prototyping of a microfluidic device for the surfactant free encapsulation of human liver cells (HepG2 cell line) in gelatin microgels, for the purpose of 3D tissue mimics in high-throughput cytotoxicity screening. Chips with rectangular channels of approximately 260 μm high by 350 μm wide produced a droplet size of 130±12 μm at a rate of 7.9±0.6 drops per second. Integrated water heating and cooling systems were efficient at regulating channel temperature, preventing the coalescence of droplets within the device without any need for surfactants. HepG2 cell viability two hours after microgel generation was 96.5%. © 2021 IEEE.
document
Van De Loosdrecht, M. M.; Abelmann, L.; Ten Haken, B.;
Biomedical Physics and Engineering Express,
Volume 7, Issue 1, 2020. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.1088/2057-1976/abce90
Keywords: ...
Humans; Magnetic Fields; Magnetics; Magnetite Nanoparticles; Signal-To-Noise Ratio; Harmonic analysis; Iron oxides; Magnetometry; Nanomagnetics; superparamagnetic iron oxide nanoparticle; magnetite nanoparticle; Clinical application; Detection methods; Experimental comparison; External magnetic field; Field strengths; Magnetic detection; Nonlinear magnetic response; Nonlinear magnetics; Second harmonic detection; Superparamagnetic iron oxide nanoparticles; Article; excitation; intermethod comparison; magnetic particle spectroscopy; magnetometry; signal noise ratio; spectroscopy; human; magnetic field; magnetism; signal noise ratio; Signal to noise ratio.
Abstract: ...
Superparamagnetic iron oxide nanoparticles (SPIONs) are promising for clinical applications, because they have a characteristic nonlinear magnetic response when an external magnetic field is applied. This nonlinearity enables the distinct detection of SPIONs and makes measurements less sensitive to the human body and surgical steel instruments. In clinical applications, only a limited field strength for the magnetic detection is allowed. The signal to noise ratios (SNRs) of four nonlinear magnetic detection methods are compared. These methods include differential magnetometry and three variations of magnetic particle spectroscopy: frequency mixing, second harmonic detection and third harmonic detection. All methods were implemented on the same hardware and experimentally compared for various field strengths. To make the comparison fair, the same power was supplied to the excitation coil each time. In general, the SNR increases with increasing field strength. The SNR per drive field of all methods stabilizes or even decreases for field strengths above 6 mT. The second harmonic detection has the best SNR and the most room for improvement. © 2020 The Author(s). Published by IOP Publishing Ltd.
document
Sung, Baeckkyoung; Yan, Huan; Kim, Chanjoong; Abelmann, Leon;
Physics Letters, Section A: General, Atomic and Solid State Physics,
Volume 384, Issue 36, 2020. All Open Access, Green Open Access. DOI: 10.1016/j.physleta.2020.126927
Keywords: ...
Aggregates; Crystal structure; Glass transition; High resolution transmission electron microscopy; Iron metallography; Magnetic nanoparticles; Metal nanoparticles; Nematic liquid crystals; Textures; Thermotropic liquid crystals; Aggregated structure; Cryogenic transmission electron microscopy; Iron oxide nanoparticle; Local distributions; Local heterogeneity; Nematic isotropic phase transition; Nematic-isotropic; Polarized microscopy; Iron oxides.
Abstract: ...
We elucidate the local distribution and aggregated structure of iron oxide nanoparticles (IONPs; 6 nm in diameter) doped in the matrix of a nematic liquid crystal (LC), 4-cyano-4'-pentylbiphenyl, utilizing in situ cryogenic transmission electron microscopy and polarized light microscopy. We show that tens of IONPs aggregate into a sphere-like morphology, and the aggregates combine into elongated clusters with a length of hundreds of nm. With the IONP-doped LC matrix confined to a thin glass cell, we study the nematic-isotropic (N-I) phase transition, and suggest that local heterogeneity of LC textures as seen in polarized microscopy is caused by the existence of IONP aggregate clusters. These clusters act also as nuclei for the formation of isotropic domains upon heating. © 2020 Elsevier B.V.
document
L{\"o}thman, Per A.; Hageman, Tijmen A. G.; Elwenspoek, Miko C.; Krijnen, Gijs J. M.; Mastrangeli, Massimo; Manz, Andreas; Abelmann, Leon;
Advanced Materials Interfaces,
Volume 7, Issue 5, 2020. All Open Access, Green Open Access. DOI: 10.1002/admi.201900963
Keywords: ...
Boltzmann equation; Higher order statistics; Kinetic energy; Random processes; Self assembly; Stochastic systems; Thermodynamics; Three dimensional computer graphics; Turbulence; Turbulent flow; Boltzmann distribution; Boltzmann statistics; Directional component; Macroscopic particles; magnetics; Self assembly process; Thermodynamic description; Thermodynamic theory; Kinetics.
Abstract: ...
The extent to which one can use a thermodynamic description of turbulent flow as a source of stochastic kinetic energy for 3D self-assembly of magnetically interacting macroscopic particles is investigated. It is confirmed that the speed of the objects in the flow field generated in this system obeys the Maxwell–Boltzmann distribution, and their random walk can be defined by a diffusion coefficient following from the Einstein relation. However, it is discovered that the analogy with Brownian dynamics breaks down when considering the directional components of the velocity. For the vectorial components, neither the equipartition theorem nor the Einstein relation is obeyed. Moreover, the kinetic energy estimated from the random walk of individual objects is one order of magnitude higher than the value estimated from Boltzmann statistics on the interaction between two spheres with embedded magnets. These results show that introducing stochastic kinetic energy into a self-assembly process by means of turbulent flow can to a great extent be described by standard thermodynamic theory, but anisotropies and the specific nature of the interactions need to be taken into account. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
document
Abelmann, Leon; Hageman, Tijmen A. G.; L{\"o}thman, Per A.; Mastrangeli, Massimo; Elwenspoek, Miko C.;
Science Advances,
Volume 6, Issue 19, 2020. All Open Access, Gold Open Access, Green Open Access. DOI: 10.1126/sciadv.aba2007
Keywords: ...
Crystals; Antiparallel state; Dipolar forces; Dipolar interaction; Micrometer ranges; One-dimensional chains; Regular structure; Three-dimensional crystals; Three-dimensional structure; article; controlled study; crystal; dipole; tumor spheroid; Self assembly.
Abstract: ...
Interaction between dipolar forces, such as permanent magnets, generally leads to the formation of one-dimensional chains and rings. We investigated whether it was possible to let dipoles self-assemble into three-dimensional structures by encapsulating them in a shell with a specific shape. We found that the condition for self-assembly of a three-dimensional crystal is satisfied when the energies of dipoles in the parallel and antiparallel states are equal. Our experiments show that the most regular structures are formed using cylinders and cuboids and not by spheroids. This simple design rule will help the self-assembly community to realize three-dimensional crystals from objects in the micrometer range, which opens up the way toward previously unknown metamaterials. Copyright © 2020 The Authors,
document
Solsona, Miguel; Nieuwelink, Anne-Eva; Odijk, Mathieu; Meirer, Florian; Abelmann, Leon; Olthuis, Wouter; Weckhuysen, Bert M.; van den Berg, Albert;
conference, 2020.
Keywords: ...
Catalyst activity; Catalysts; Fluid catalytic cracking; Magnetic moments; Iron concentrations; Magnetophoresis; On chips; Particle trajectories; Screening.
Abstract: ...
We demonstrate an on-chip particle activity sorter, focused on iron concentration and based on magnetophoresis. This device was used for fast sorting of stepwise homogenously distributed [Fe]s. The preliminary results are very encouraging. We show that we can sort particles on magnetic moment, with a spread of a factor of four. XRF measurements confirm that the spread in magnetic moment is due to an increase in [Fe] concentration. This results fits well with particle trajectory simulations. © 17CBMS-0001.
document
Solsona, Miguel; Nieuwelink, Anne-Eva; Papadimitriou, Vasileios A.; Eijkel, Jan C. T.; Meirer, Florian; Abelmann, Leon; Olthuis, Wouter; Weckhuysen, Bert M.; van den Berg, Albert;
conference, 2020.
Keywords: ...
Catalysts; Fluid catalytic cracking; Polarization; Concentration polarization; Deactivation process; Pore blockages; Porous catalysts; Single particle; Catalyst deactivation.
Abstract: ...
Understanding the deactivation process in porous catalysts is of tremendous economic significance. We demonstrate the feasibility of using the concentration polarization method to obtain the pore accessibility distribution at single particle level for the first time. By using this technique we could measure the pore blockage caused by Fe in fluid catalytic cracking particles as evidenced by correlating it to the activity. We expect this new single particle technique to increase our understanding of the deactivation processes occurring in porous catalysts. © 17CBMS-0001.
document
Hageman, Tijmen A. G.; Pichel, Marc P.; L{\"o}thman, Per A.; Cho, Jiung; Choi, Miri; Korkmaz, Nuriye; Manz, Andreas; Abelmann, Leon;
Archives of Microbiology,
Volume 201, Issue 10, pp. 1427 – 1433, 2019. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.1007/s00203-019-01713-0
Keywords: ...
Bacteriological Techniques; Magnetospirillum; Microfluidics; Time Factors; article; illumination; magnetic field; Magnetospirillum gryphiswaldense; nonhuman; rotation; Magnetospirillum; microbiological examination; microfluidics; physiology; procedures; time factor.
Abstract: ...
We controlled and observed individual magneto-tactic bacteria (Magnetospirillum gryphiswaldense) inside a 5μm-high microfluidic channel for over 4 h. After a period of constant velocity, the duration of which varied between bacteria, all observed bacteria showed a gradual decrease in their velocity of about 25nm/s2. After coming to a full stop, different behaviour was observed, ranging from rotation around the centre of mass synchronous with the direction of the external magnetic field, to being completely immobile. Our results suggest that the influence of the high-intensity illumination and the presence of the channel walls are important parameters to consider when performing observations of such long duration. © 2019, The Author(s).
document
Solsona, Miguel; Keizer, Hans; de Boer, Hans L.; Klein, Yannick P.; Olthuis, Wouter; Abelmann, Leon; van den Berg, Albert;
conference, 2019.
Keywords: ...
Magnetic materials; Janus particles; Magnus forces; Micro-particles; Rotating magnetic fields; Shape anisotropy; Trajectory deflection; Magnetic anisotropy.
Abstract: ...
Here we report the first study of the trajectory deflection of Janus particles rotated with a rotating magnetic field inside a liquid. Also, we developed a model able to predict the deflection of these particles. We believe that the Magnus force can be used to sort cells and microparticles based on shape, size or even magnetic material shape anisotropy. © 2019 CBMS-0001.
document
Pichel, M. P.; Hageman, T. A. G.; Khalil, I. S. M.; Manz, A.; Abelmann, L.;
Journal of Magnetism and Magnetic Materials,
Volume 460, pp. 340 – 353, 2018. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2018.04.004
Keywords: ...
Bacteria; Control engineering; Drag; Fluidic devices; Microfluidics; Torque; Trajectories; Accurate measurement; Drag torque; Magnetic response; Magnetic torques; Magnetospirillum gryphiswaldense; Magnetotactic Bacteria; Microfluidic channel; Rotating magnetic fields; Magnetism.
Abstract: ...
In this study we modelled and measured the U-turn trajectories of individual magnetotactic bacteria under the application of rotating magnetic fields, ranging in amplitude from 1 to 12 mT. The model is based on the balance between rotational drag and magnetic torque. For accurate verification of this model, bacteria were observed inside 5 μm tall microfluidic channels, so that they remained in focus during the entire trajectory. From the analysis of hundreds of trajectories and accurate measurements of bacteria and magnetosome chain dimensions, we confirmed that the model is correct within measurement error. The resulting average rate of rotation of Magnetospirillum gryphiswaldense is 0.74 ± 0.03 rad/mTs. © 2018 Elsevier B.V.
document
Solsona, Miguel; Nieuwelink, Anne-Eva; Meirer, Florian; Abelmann, Leon; Odijk, Mathieu; Olthuis, Wouter; Weckhuysen, Bert M.; van den Berg, Albert;
Angewandte Chemie - International Edition,
Volume 57, Issue 33, pp. 10589 – 10594, 2018. All Open Access, Green Open Access. DOI: 10.1002/anie.201804942
Keywords: ...
Catalysis; Catalysts; Fluid catalytic cracking; Iron; Magnetic moments; Magnetic properties; Microfluidics; Screening; Catalyst particles; Deactivation process; Fluid catalytic cracking(FCC); High throughput; Magnetophoresis; Particle heterogeneity; Particle sorting; Solid catalysts; Catalytic cracking.
Abstract: ...
A better understanding of the deactivation processes taking place within solid catalysts is vital to design better ones. However, since inter-particle heterogeneities are more a rule than an exception, particle sorting is crucial to analyse single catalyst particles in detail. Microfluidics offers new possibilities to sort catalysts at the single particle level. Herein, we report a first-of-its-kind 3D printed magnetophoretic chip able to sort catalyst particles by their magnetic moment. Fluid catalytic cracking (FCC) particles were separated based on their Fe content. Magnetophoretic sorting shows that large Fe aggregates exist within 20 % of the FCC particles with the highest Fe content. The availability of Brønsted acid sites decreases with increasing Fe content. This work paves the way towards a high-throughput catalyst diagnostics platform to determine why specific catalyst particles perform better than others. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
document
Ipparthi, Dhananjay; Hageman, Tijmen A. G.; Cambier, Nicolas; Sitti, Metin; Dorigo, Marco; Abelmann, Leon; Mastrangeli, Massimo;
Physical Review E,
Volume 98, Issue 4, 2018. All Open Access, Green Open Access. DOI: 10.1103/PhysRevE.98.042137
Keywords: ...
Kinetic energy; Molecular dynamics; Self assembly; Diffusive motions; Experimental system; Macroscopic particles; Random walk modeling; Translational velocity; Two dimensional spaces; Two-dimension; Kinetics.
Abstract: ...
We present an experimental study of the kinetics of orbitally-shaken, sliding macroscopic particles confined to a two-dimensional space bounded by walls. Discounting the forcing action of the external periodic actuation, the particles undergo a qualitative transition from a ballistic to a diffusive motion regime with time. Despite the deterministic input of kinetic energy provided by the shaker, the particles show translational velocities and diffusivity consistent with a confined random walk model. Such experimental system may therefore represent a suitable macroscopic analog to investigate aspects of molecular dynamics and self-assembly. © 2018 American Physical Society.
document
Hageman, T. A. G.; L{\"o}thman, P. A.; Dirnberger, M.; Elwenspoek, M. C.; Manz, A.; Abelmann, L.;
Journal of Applied Physics,
Volume 123, Issue 2, 2018. All Open Access, Green Open Access. DOI: 10.1063/1.5007029
Keywords: ...
Boltzmann equation; Brownian movement; Flow of water; Spheres; Characteristic time; Macroscopic self-assembly; Maxwell-Boltzmann distribution; Physical simulator; Random walk modeling; Self assembly process; Trajectory analysis; Turbulent water flow; Self assembly.
Abstract: ...
We built and characterised a macroscopic self-assembly reactor that agitates magnetic, centimeter-sized particles with a turbulent water flow. By scaling up the self-assembly processes to the centimeter-scale, the characteristic time constants also drastically increase. This makes the system a physical simulator of microscopic self-assembly, where the interaction of inserted particles is easily observable. Trajectory analysis of single particles reveals their velocity to be a Maxwell-Boltzmann distribution and it shows that their average squared displacement over time can be modelled by a confined random walk model, demonstrating a high level of similarity to the Brownian motion. The interaction of two particles has been modelled and verified experimentally by observing the distance between two particles over time. The disturbing energy (analogue to temperature) that was obtained experimentally increases with sphere size and differs by an order of magnitude between single-sphere and two-sphere systems (approximately 80 μJ versus 6.5 μJ, respectively). © 2018 Author(s).
document
Duan, Lian; Huang, Xiaomin; Djuemo, Irving; Abelmann, Leon; Manz, Andreas; Yobas, Levent;
conference, 2018.
Keywords: ...
Aerosols; Drop formation; Glass; Mass spectrometry; Silicon; Direct observations; Electrospray ionization (ESI); Electrospraying; Emitter; Low resolution; Micro-fabrication techniques; Nanonozzle; Separation chip; Electrospray ionization.
Abstract: ...
We demonstrate here self-enclosed integrated glass nanonozzle emitters on silicon for electrospray ionization and present a technique for direct experimental observation of electrospraying small droplets from such emitters. The emitters feature a 500-nm-radius cylindrical lumen batch-fabricated using a low-resolution photolithography and standard microfabrication techniques. Thus, it is amenable to integration with an upstream separation chip. Copyright© (2018) by Chemical and Biological Microsystems Society.All rights reserved.
document
El-Din, Nermeen S.; Klingner, Anke; Ewis, Mohamed; Yousry, Noura; Ahmed, Ola; Gomaa, Iman; Hageman, Tijmen; Pichel, Marc; Mitwally, Mohamed E.; Abelmann, Leon; Khalil, Islam S. M.;
conference, 2018. All Open Access, Green Open Access. DOI: 10.1109/EMBC.2018.8512676
Keywords: ...
Humans; Magnetospirillum; MCF-7 Cells; Models, Biological; Movement; Oxygen; oxygen; biological model; human; Magnetospirillum; MCF-7 cell line; metabolism; movement (physiology); physiology.
Abstract: ...
We investigate the sensing capabilities of magnetotactic bacteria (Magnetospirillum gryphiswaldense strain MSR1) to MCF-7 breast cancer cells. Cancer cells are allowed to grow inside a capillary tube with depth of 200 μ m and motion of magnetotactic bacteria is investigated under the influence of oxygen gradient and geomagnetic field. The influence of cancer cells is modeled to predict the oxygen gradient within the capillary tube in three-dimensional space. Our experimental motion analysis and count of motile magnetotactic bacteria indicate that they migrate towards less-oxygenated regions within the vicinity of cancer cells. Bands of magnetotactic bacteria with average concentration of 18.8±2.0% are observed in close proximity to MCF-7 cells (h = 20~ μ m), whereas the concentration at proximity of 190~ μ m is 5.0 ± 6.8%. © 2018 IEEE.
document
Vries, Jeroen De; Bolhuis, Thijs; Abelmann, Leon;
New Journal of Physics,
Volume 19, Issue 9, 2017. All Open Access, Gold Open Access, Green Open Access. DOI: 10.1088/1367-2630/aa8082
Keywords: ...
Anisotropy; Chemical activation; Energy barriers; Extrapolation; Magnetic materials; Magnetism; Temperature distribution; Anomalous hall effects; Magnetic elements; Magnetic reversal; Perpendicular anisotropy; Switching field distribution; Temperature dependence; Temperature dependent; Temperature-dependent measurements; Switching.
Abstract: ...
Using the highly sensitive anomalous Hall effect we have been able to measure the reversal of a single magnetic island, of diameter 220 nm, in an array consisting of more than 80 of those islands. By repeatedly traversing the hysteresis loop, we measured the thermally induced fluctuation of the switching field of the islands at the lower and higher ends of the switching field distribution. Based on a novel easy-to-use model, we determined the switching field in the absence of thermal activation, and the energy barrier in the absence of an external field from these fluctuations. By measuring the reversal of individual dots in the array as a function of temperature, we extrapolated the switching field and energy barrier down to 0 K. The extrapolated values are not identical to those obtained from the fluctation of the switching field at room temperature, because the properties of the magnetic material are temperature dependent. As a result, extrapolating from temperature dependent measurements overestimates the energy barrier by more than a factor of two. To determine fundamental parameters of the energy barrier between magnetisation states, measuring the fluctuation of the reversal field at the temperature of application is therefore to be preferred. This is of primary importance to applications in data storagea and magnetic logic. For instance in fast switching, where the switching field in the absence of thermal activation plays a major role, or in long term data stability, which is determined by the energy barrier in the absence of an external field. © 2017 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
document
Abelmann, Leon;
, 2017. DOI: 10.1016/B978-0-12-803224-4.00029-7
Keywords: ...
Magnetism; Nanocantilevers; Scanning probe microscopy; Coated tips; Fourier; Magnetic stray fields; Resonating cantilevers; Tip-sample distance; Magnetic force microscopy.
Abstract: ...
Magnetic force microscopy (MFM) is a scanning probe microscopy technique which images the magnetic stray field above flat specimens. This article is intended for researchers either working with MFM instrumentation or analysing the results measured by operators. We will discuss the theory behind the technique including the different measurement modes, image formation and techniques for interpreting the images. Next the MFM instrumentation will be discussed, including system aspects, feedback loops and available MFM tips. An extensive list of literature for further reading is provided. © 2017 Elsevier Ltd. All rights reserved.
document
Khalil, Islam S. M.; Tabak, Ahmet Fatih; Hageman, Tijmen; Ewis, Mohamed; Pichel, Marc; Mitwally, Mohamed E.; El-Din, Nermeen Serag; Abelmann, Leon; Sitti, Metin;
conference, 2017. DOI: 10.1109/ICRA.2017.7989705
Keywords: ...
Robotics; Targeted drug delivery; Background flow; Controlled motions; Hydrodynamic model; Magnetospirillum gryphiswaldense; Magnetotactic Bacteria; Microfluidic chip; Resistive force theory; Surface interactions; Bacteria.
Abstract: ...
Magnetotactic bacteria have the potential to controllably reach stagnant fluids inside the human body and achieve targeted drug delivery. In this application, motion of the magnetotactic bacteria is influenced by the near-surface effects such as the background flows and surface interactions. Here, we provide a hydrodynamic model of bipolarly-flagellated magnetotactic bacteria (Magnetospirillum gryphiswaldense strain MSR-1) based on the resistive-force theory to resemble the helical body and the two flagella bundles, and investigate their swimming characteristics in two environments, i.e., free-space and near flat walls. The free-space is studied using capillary tubes with depth of 200 ßm, whereas the effect of the flat walls is investigated using microfluidic chips with depth of 5 μm. We find that the linear speeds of bacteria near- and far-surface are 36±16.4 μm/s (mean±s.d.) and 46±6.8 μm/s, respectively, whereas their respective angular velocities are 12.5±5.7 rad/s and 13.5±5.0 rad/s. © 2017 IEEE.
document
Woldering, L{\' e}on A.; Been, Auke J.; Alink, Laurens; Abelmann, Leon;
Physica Status Solidi - Rapid Research Letters,
Volume 10, Issue 2, pp. 176 – 184, 2016. All Open Access, Green Open Access. DOI: 10.1002/pssr.201510298
Keywords: ...
Hydrophilicity; Hydrophobicity; Magnetic levitation; Magnetic levitation vehicles; Nanotechnology; Silicon; 3D self-assembly; Functional structure; Hydrophobic interactions; Macro-particles; Paramagnetic fluid; Polymer spheres; Scaling limits; Silicon particles; Self assembly.
Abstract: ...
Today's micro- and nano-fabrication is essentially two-dimensional, with very limited possibilities of accessing the third dimension. The most viable way to mass-fabricate functional structures at the nano-scale, such as electronics or MEMS, with equal feature sizes in all directions, is by three-dimensional self-assembly. Up to now, three-dimensional self-assembly has mainly been restricted to crystals of polymer spheres. We report on two- and three-dimensional self-assembly of silicon cubes, levitated in a paramagnetic fluid. We demonstrate the benefits of templating and study the effect of a change in hydrophilicity of the cubes. These experiments bring us one step closer to three-dimensional self-assembly of anisotropic, semiconducting units, which is a crucial milestone in overcoming the scaling limits imposed by contemporary 2D microfabrication. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
document
Legrain, Antoine; Berenschot, Erwin J. W.; Abelmann, Leon; Bico, Jos{\' e}; Tas, Niels R.;
Soft Matter,
Volume 12, Issue 34, pp. 7186 – 7194, 2016. All Open Access, Green Open Access. DOI: 10.1039/c6sm00910g
Keywords: ...
Silicon nitride; Silicon wafers; 3D microstructures; Batch fabrication; Capillary assembly; Controllable structures; Macroscopic scale; Micrometer scale; Model experiments; Self-assembly technique; Self assembly.
Abstract: ...
We show the self-assembly through twisting and bending of side by side ribbons under the action of capillary forces. Micro-ribbons made of silicon nitride are batch assembled at the wafer scale. We study their assembly as a function of their dimensions and separating distance. Model experiments are carried out at the macroscopic scale where the tension in ribbons can easily be tuned. The process is modeled considering the competition between capillary, elastic and tension forces. Theory shows a good agreement for macroscale assemblies, while the accuracy is within 30% at the micrometer scale. This simple self-assembly technique yields highly symmetric and controllable structures which could be used for batch fabrication of functional 3D micro-structures. © 2016 The Royal Society of Chemistry.
document
Nazeer, H.; Nguyen, M. D.; Rijnders, G.; Abelmann, L.; Sardan Sukas, {\"O}.;
Microelectronic Engineering,
Volume 161, pp. 56 – 62, 2016. All Open Access, Green Open Access. DOI: 10.1016/j.mee.2016.04.004
Keywords: ...
Crystal orientation; Deposition; Elastic moduli; Epitaxial growth; Lead; Nanocantilevers; Pulsed laser deposition; Pulsed lasers; Residual stresses; Silicon; Thermal expansion; X ray diffraction; Cantilever bending; Crystal direction; Mechanical parameters; Preferred orientations; Resonance frequencies; Silicon cantilever; Thin film composition; X-ray diffraction data; Thin films.
Abstract: ...
We investigated the residual stress and Young's modulus of Pb(ZrxTi1 - x)O3 (PZT) thin films with a (110) preferred orientation and a composition x ranging from 0.2 to 0.8. The films are grown by pulsed laser deposition on silicon cantilevers aligned along the <110> and <100> silicon crystal directions. Changes in resonance frequency and static bending of the cantilevers are used to determine the Young's modulus and residual stress respectively. The Young's modulus was found to be in the range of 100-200 GPa. The residual stress is tensile and shows a sharp increase from about 50 to 250 MPa at a composition of x = 0.2 to 0.4. These mechanical parameters clearly depend on the cantilever orientation with respect to the silicon crystal, which we suspect to be linked to the epitaxial growth of the films. The variation in stress with composition can be explained by the difference in thermal expansion between silicon and PZT, if we assume an intrinsic stress of 200-300 MPa to be already present immediately after deposition. Strain calculated from X-ray diffraction data leads to unreasonably high residual stress values, at least one order of magnitude higher than measured by cantilever bending. © 2016 Elsevier B.V. All rights reserved.
document
Van Den Beld, Wesley T. E.; Cadena, Natalia L.; Bomer, Johan; De Weerd, Eddy L.; Abelmann, Leon; Van Den Berg, Albert; Eijkel, Jan C. T.;
Lab on a Chip,
Volume 15, Issue 13, pp. 2872 – 2878, 2015. All Open Access, Green Open Access. DOI: 10.1039/c5lc00199d
Keywords: ...
Magnetics; Microfluidic Analytical Techniques; Microspheres; Models, Theoretical; Rotation; ferromagnetic material; microsphere; polystyrene; algorithm; Article; dipole; flow measurement; flow rate; fluid flow; force; lab on a chip; magnetic field; microfluidics; microscopy; priority journal; rotation; viscosity; devices; magnetism; microfluidic analysis; theoretical model.
Abstract: ...
We demonstrate a novel, flexible and programmable method to pump liquid through microchannels in lab-on-a-chip systems without the use of an external pump. The pumping principle is based on the rotation of ferromagnetic Janus microspheres around permalloy disks, driven by an external rotating magnetic field. By placing the disks close to the edge of the microchannel, a pumping rate of at least 0.3 nL min-1 was measured using tracking microspheres. Geometric programming of the pumping direction is possible by positioning the magnetic disk close to the side wall. A second degree of freedom in the pumping direction is offered by the rotational direction of the external magnetic field. This method is especially suited for flow-controlled recirculation of chemical and biological species in microchannels - for example, medium recirculation in culture chambers - opening the way towards novel, portable, on-chip applications without the need for external fluidic or electrical connections. © The Royal Society of Chemistry.
document
Nazeer, Hammad; Bhaskaran, Harish; Woldering, L{\' e}on A.; Abelmann, Leon;
Thin Solid Films,
Volume 592, pp. 69 – 75, 2015. All Open Access, Green Open Access. DOI: 10.1016/j.tsf.2015.08.049
Keywords: ...
Antimony compounds; Digital storage; Elastic moduli; Germanium compounds; Residual stresses; Strain; Tellurium compounds; Crucial parameters; GeSbTe; Micro-cantilevers; Non-volatile; Non-volatile data; Phase Change; Phase change films; Phase change thin films; Phase change materials.
Abstract: ...
The mechanical properties of phase change materials alter when the phase is transformed. In this paper, we report on experiments that determine the change in crucial parameters such as Young's modulus and residual stress for two of the most widely employed compositions of phase change films, Ge1Sb2Te4 and Ge2Sb2Te5, using an accurate microcantilever methodology. The results support understanding of the exact mechanisms that account for the phase transition, especially with regard to stress, which leads to drift in non-volatile data storage. Moreover, detailed information on the change in mechanical properties will enable the design of novel low-power nonvolatile MEMS. © 2015 Elsevier B.V.
document
Krijnen, B.; Brouwer, D. M.; Abelmann, L.; Herder, J. L.;
Sensors and Actuators, A: Physical,
Volume 234, pp. 321 – 330, 2015. All Open Access, Green Open Access. DOI: 10.1016/j.sna.2015.09.005
Keywords: ...
Control; Frequency domain analysis; Low pass filters; Mechanisms; MEMS; Notch filters; Q factor measurement; Thermal conductivity; Vacuum; Closed-loop behavior; Electrostatic comb drives; Integral controllers; Integrated sensors; Q-factors; Reduced resolution; Thermal displacement sensors; Vacuum environment; Controllers.
Abstract: ...
We investigate the applicability of a MEMS stage in a vacuum environment. The stage is suspended by a flexure mechanism and is actuated by electrostatic comb-drives. The position of the stage is measured by an integrated sensor based on the conductance of heat through air. The vacuum behavior of the sensor and the stage is identified. A model for thermal conductivity and viscous damping as a function of the vacuum pressure is presented and validated by measuring the decreasing sensor response and the increasing Q-factor for decreasing pressure. We have identified the system in the frequency domain, which is used to compare the closed-loop behavior with three different controllers: an integral controller, an integral controller with low-pass filter, and an integral controller with notch filter. The integral controller can become unstable due to the high Q-factor in vacuum. Adding a low-pass or a notch filter improves the stability at low pressures. Since the integral controller with notch filter shows the lowest settling time, this is the preferred controller. Overall, we are able to control the position of the MEMS stage at a pressure of 1 mbar with a reduced resolution of approximately 1.1 μm, but with a good settling time of 2.2 ms. © 2015 Elsevier B.V.© 2015 Elsevier B.V. All rights reserved.
document
Park, J. K.; Campos, C. D. M.; Neu{\v z}il, P.; Abelmann, L.; Guijt, R. M.; Manz, A.;
Lab on a Chip,
Volume 15, Issue 17, pp. 3495 – 3502, 2015. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.1039/c5lc00523j
Keywords: ...
Citric Acid; Equipment Design; Fluorescein; Isotachophoresis; Lab-On-A-Chip Devices; Models, Chemical; Spectrometry, Mass, Electrospray Ionization; citric acid; fluorescein; analytical equipment; Article; electric field; electrospray mass spectrometry; free flow isotachophoresis; free flow isotachophoresis device; hydrodynamics; isotachophoresis; microfluidics; microtechnology; optical resolution; priority journal; proteomics; chemical model; devices; electrospray mass spectrometry; equipment design; isotachophoresis; lab on a chip.
Abstract: ...
We present the online coupling of a free-flow isotachophoresis (FFITP) device to an electrospray ionization mass spectrometer (ESI-MS) for continuous analysis without extensive sample preparation. Free-flow-electrophoresis techniques are used for continuous electrophoretic separations using an electric field applied perpendicular to the buffer and sample flow, with FFITP using a discontinuous electrolyte system to concurrently focus a target analyte and remove interferences. The online coupling of FFITP to ESI-MS decouples the separation and detection timeframe because the electrophoretic separation takes place perpendicular to the flow direction, which can be beneficial for monitoring (bio)chemical changes and/or extensive MSn studies. We demonstrated the coupling of FFITP with ESI-MS for simultaneous concentration of target analytes and sample clean-up. Furthermore, we show hydrodynamic control of the fluidic fraction injected into the MS, allowing for fluidically controlled scanning of the ITP window. Future applications of this approach are expected in monitoring biochemical changes and proteomics. © The Royal Society of Chemistry 2015.
document
Pondman, Kirsten M.; Bunt, Nathan D.; Maijenburg, A. Wouter; Van Wezel, Richard J. A.; Kishore, Uday; Abelmann, Leon; Ten Elshof, Johan E.; Ten Haken, Bennie;
Journal of Magnetism and Magnetic Materials,
Volume 380, pp. 299 – 306, 2015. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2014.10.101
Keywords: ...
Blood; Cell culture; Drug delivery; Drug interactions; Endothelial cells; Hemodynamics; Magnetic moments; Magnetism; Magnets; Nanoparticles; Nanowires; Toxicity; Endothelial cell line; High magnetic moments; Immune response; In-vivo experiments; Magnetic drug delivery; Magnetic nano-particles; Negative side effects; Systemic administration; Nanomagnetics.
Abstract: ...
Magnetic drug delivery is a promising method to target a drug to a diseased area while reducing negative side effects caused by systemic administration of drugs. In magnetic drug delivery a therapeutic agent is coupled to a magnetic nanoparticle. The particles are injected and at the target location withdrawn from blood flow by a magnetic field. In this study a FePd nanowire is developed with optimised properties for magnetic targeting. The nanowires have a high magnetic moment to reduce the field gradient needed to capture them with a magnet. The dimensions and the materials of the nanowire and coating are such that they are dispersable in aqueous media, non-cytotoxic, easily phagocytosed and not complement activating. This is established in several in-vitro tests with macrophage and endothelial cell lines. Along with the nanowires a magnet is designed, optimised for capture of the nanowires from the blood flow in the hind leg of a rat. The system is used in a pilot scale in-vivo experiment. No negative side effects from injection of the nanowires were found within the limited time span of the experiment. In this first pilot experiment no nanowires were found to be targeted by the magnet, or in the liver, kidneys or spleen, most likely the particles were removed during the fixation procedure. © 2014 Elsevier B.V. All rights reserved.
document
Krijnen, Bram; Swinkels, Koen R.; Brouwer, Dannis M.; Abelmann, Leon; Herder, Just L.;
Journal of Microelectromechanical Systems,
Volume 24, Issue 5, pp. 1659, 2015. All Open Access, Green Open Access. DOI: 10.1109/JMEMS.2015.2452791
document
Legrain, A.; Berenschot, J. W.; Tas, N. R.; Abelmann, L.;
Microelectronic Engineering,
Volume 140, pp. 60 – 66, 2015. All Open Access, Green Open Access. DOI: 10.1016/j.mee.2015.06.004
Keywords: ...
Electrodes; Platinum; Silicon nitride; Capillary force; Conductive electrodes; Different layers; Electronic functionality; Fabrication yield; Folding process; Plasma cleaning; Platinum electrodes; Hinges.
Abstract: ...
Recently, we demonstrated controllable 3D self-folding by means of capillary forces of silicon-nitride micro-objects made of rigid plates connected to each other by flexible hinges (Legrain et al., 2014). In this paper, we introduce platinum electrodes running from the substrate to the plates over these bendable hinges. The fabrication yield is as high as (77 ± 2)% for hinges with a length less than 75 μm. The yield reduces to (18 ± 2)% when the length increases above 100 μm. Most of the failures in conductivity are due to degradation of the platinum/chromium layer stack during the final plasma cleaning step. The bi-layer hinges survive the capillary folding process, even for extremely small bending radii of 5 μm, nor does the bending have any impact on the conductivity. Stress in the different layers deforms the hinges, which does not affect the conductivity. Once assembled, the conductive hinges can withstand a current density of (1.6 ± 0.4) × 106 A/cm2. This introduction of conductive electrodes to elastocapillary self-folded silicon-based micro-objects extends the range of their possible applications by allowing an electronic functionality of the folded parts. © 2015 Elsevier B.V.All rights reserved.
document
Geerlings, Jo{\" e}l; Sarajlic, Edin; Berenschot, Erwin J. W.; Sanders, Remco G. P.; Siekman, Martin H.; Abelmann, Leon; Tas, Niels R.;
Applied Physics Letters,
Volume 107, Issue 12, 2015. All Open Access, Green Open Access, Hybrid Gold Open Access. DOI: 10.1063/1.4931354
Keywords: ...
Electric fields; Liquids; Nanotechnology; Sodium deposits; Sodium sulfate; Substrates; Wetting; Contact less; Contactless deposition; Deposition current; Liquid deposition; Non-contact; Polar liquids; Scanning probes; Simple modeling; Deposition.
Abstract: ...
A technique for contactless liquid deposition on the nanoscale assisted by an electric field is presented. By the application of a voltage between the liquid inside a (FluidFM) nanofountain pen AFM probe and a substrate, accurate contactless deposition is achieved. This technique allows for the deposition of polar liquids on non-wetting substrates. Sodium sulfate dried deposits indicate that the spot size and height increases with t0.33±0.04 and t0.35±0.10, respectively. The minimum observed diameter was 70nm. By measuring the probe deflection and the electric deposition current, we confirm that deposition is truly non-contact. We propose a simple model based on a constant stream of liquid to the substrate, which explains our observations qualitatively. © 2015 Author(s).
document
Krijnen, Bram; Swinkels, Koen R.; Brouwer, Dannis M.; Abelmann, Leon; Herder, Just L.;
Journal of Microelectromechanical Systems,
Volume 24, Issue 6, pp. 1720 – 1729, 2015. All Open Access, Green Open Access. DOI: 10.1109/JMEMS.2015.2432054
Keywords: ...
Electromechanical devices; Electrostatic actuators; Electrostatics; Mechanisms; MEMS; Transfer functions; Displacement sensor; Electrostatic comb drives; Fabrication process; Flexure mechanism; Geometric transfer functions; Kinematic relations; Micro electromechanical system (MEMS); Positioning stage; Position control.
Abstract: ...
In this paper, we design, fabricate, and validate a large-stroke 3-degree-of-freedom (DOF) positioning stage with integrated displacement sensors for feedback control in a single-mask microelectromechanical systems (MEMS) fabrication process. Three equal shuttles exactly define the position of the stage in x, y, and Rz. The kinematic relation between the shuttle positions and the stage position is given by the geometric transfer function. By increasing the order of this geometric transfer function, the stage error can be reduced. Each shuttle consists of a flexure mechanism, a position sensor, and electrostatic comb drive actuators for actuation along a straight line. The range of motion of the stage is limited by electrostatic pull-in of these comb drives. Three parameters of the stage, the leafspring length, the eccentricity, and the tangential arm, have been varied to find their influence on the stage range of motion. These simulation results can be used to design stages with different specifications. Position control of the individual shuttles is applied to control the position of the stage. The stroke of the 3DOF stage is verified up to 161 μm in x, 175 μm in y, and 325 mrad in Rz. This exceeds the range of motion of existing stages. [2014-0314] © 2015 IEEE.
document
Nazeer, Hammad; Nguyen, Minh D.; Sukas, {\"O}zlem Sardan; Rijnders, Guus; Abelmann, Leon; Elwenspoek, Miko C.;
Journal of Microelectromechanical Systems,
Volume 24, Issue 1, pp. 166 – 173, 2015. All Open Access, Green Open Access. DOI: 10.1109/JMEMS.2014.2323476
Keywords: ...
Ceramic materials; Deposition; Electromechanical devices; Lead; MEMS; Microelectromechanical devices; Piezoelectricity; Pulsed laser deposition; Pulsed lasers; Thin films; Zirconium; Compositional dependence; Coupling coefficient; Flexural resonance frequency; Piezoelectric coefficient; Piezoelectric property; Preferred orientations; PZT; Young's Modulus; Elastic moduli.
Abstract: ...
In this contribution, we report on the compositional dependence of the mechanical and piezoelectric properties of Pb(ZrxTi1-x)O3 (PZT) thin films fabricated by pulsed laser deposition (PLD). These films grow epitaxially on silicon with a (110) preferred orientation and have excellent piezoelectric properties, which make them outstanding candidates for application in microelectromechanical system devices. Vibrometric measurements on capacitors showed that the effective longitudinal piezoelectric coefficient (d33,f) of 100-nm thick PZT films has a maximum value of 72 pm/V for a composition of x = 0.52. The Young's modulus was determined by measuring the difference in the flexural resonance frequencies of cantilevers before and after the deposition of the PZT thin films. The compositional dependence of the Young's modulus shows an increase in value for the Zr-rich compositions, which is in agreement with the trend observed in their bulk ceramic counterparts. From the obtained dielectric constant and d33,f, we show that the calculated coupling coefficients of the PLD-PZT thin films have higher values for most of the compositions than their ceramic counterparts. [2013-0039] © 2014 IEEE.
document
Hageman, T. A. G.; Pichel, M. P.; Altmeyer, M. O.; Manz, A.; Abelmann, L.;
conference, 2015.
Keywords: ...
Bacteria; Control; Magnetic fields; Erase head; Magnetotactic Bacteria; Unidirectional magnetic fields; Magnetism.
Abstract: ...
We show for the first time that an alternating unidirectional magnetic field generated by a magnetic erase head allows planar manipulation of magneto-tactic bacteria (MTB), and is not restricted to parallel directions only. We used squared-shaped magnetic fields of approximately 4 mT while sweeping from 0.25 to 10 Hz, and found that at frequencies of over 3 Hz the mean orthogonal velocity becomes constant. The erase head offers a significant reduction in size and complexity over conventional manipulators. © 15CBMS-0001.
document
Khalil, Islam S. M.; Dijkslag, Herman C.; Abelmann, Leon; Misra, Sarthak;
Applied Physics Letters,
Volume 104, Issue 22, 2014. All Open Access, Green Open Access. DOI: 10.1063/1.4880035
Keywords: ...
Cobalt; Flexible structures; Frequency response; Magnetic fields; Magnetic heads; Nickel; Average speed; Cobalt-nickel; Magnetic field line; Micro robots; Propulsion mechanisms; Propulsion system; Thrust forces; Weak magnetic fields; Propulsion.
Abstract: ...
In this work, a propulsion system similar in motion to a sperm-cell is investigated. This system consists of a structure resembling a sperm-cell with a magnetic head and a flexible tail of 42 μm and 280 μm in length, respectively. The thickness, length, and width of this structure are 5.2 μm, 322 μm, and 42 μm, respectively. The magnetic head includes a 200 nm-thick cobalt-nickel layer. The cobalt-nickel layer provides a dipole moment and allows the flexible structure to align along oscillating weak (less than 5mT) magnetic field lines, and hence generates a propulsion thrust force that overcomes the drag force. The frequency response of this system shows that the propulsion mechanism allows for swimming at an average speed of 158 ± 32 μm/s at alternating weak magnetic field of 45 Hz. In addition, we experimentally demonstrate controlled steering of the flexible structure towards reference positions. © 2014 AIP Publishing LLC.
document
Geerlings, J.; Sarajlic, E.; Berenschot, J. W.; Siekman, M. H.; Jansen, H. V.; Abelmann, L.; Tas, N. R.;
Journal of Micromechanics and Microengineering,
Volume 24, Issue 10, 2014. All Open Access, Green Open Access. DOI: 10.1088/0960-1317/24/10/105013
Keywords: ...
Electrostatic actuators; Silicon nitride; AFM probe; in-plane tip; KOH etching; Video rates; Atomic force microscopy.
Abstract: ...
In this paper a micromachining method for batch fabrication of in-plane atomic force microscope (AFM) probes that consist of a sharp silicon nitride tip on a monocrystalline silicon cantilever is presented. The tips are realized by conformal deposition of silicon nitride inside an anisotropically etched cavity inside a silicon wafer. The best measured radius of the sharp tips was 8 nm. Our fabrication method is fully compatible with silicon-on-insulator (SOI) micromachining, allowing a straightforward monolithic integration of the AFM probes with high-aspect-ratio monocrystalline silicon MEMS. The fabrication method allows for lateral cantilevers, which oscillate in the plane of the fabrication wafer. This allows for simple integration of micromechanical transducers, opening the way towards dedicated probes for high speed AFMs. To demonstrate the innovation potential of this method, three different probe designs were fabricated: a plane passive AFM probe, a probe with integrated electrostatic actuator, and a probe which allows scanning on vertical sidewalls. The passive probes were successfully tested in a commercial AFM set-up. Correct operation of the probes with integrated actuator was demonstrated by actuation under a laser vibrometer. © 2014 IOP Publishing Ltd.
document
Legrain, A.; Janson, T. G.; Berenschot, J. W.; Abelmann, L.; Tas, N. R.;
Journal of Applied Physics,
Volume 115, Issue 21, 2014. All Open Access, Green Open Access. DOI: 10.1063/1.4878460
Keywords: ...
Physical properties; Physics; 3D microstructures; Bending stiffness; Fabrication process; Folded structures; Folding modeling; Hydro-mechanical; Micro-objects; Pumping systems; Silicon nitride.
Abstract: ...
We present a technique for the controllable capillary folding of planar silicon nitride templates into 3D micro-structures by means of through-wafer liquid application. We demonstrate for the first time hydro-mechanical, repeatable, actuation of capillary folded structures via the addition or retraction of water on demand. Silicon nitride objects with a central through-wafer tube are connected to a dedicated pumping system to enable assembly. When remaining wetted, structures can be assembled and reopened up to several dozens of times and still reach the same final folding angle. Objects were actuated up to 60 times without signs of wear. Extracted curves from our self-folding experiments are in agreement with our two-dimensional elastocapillary folding model. When structures are allowed to dry in between foldings, we observe an increase in the bending stiffness of the hinges, by a factor 50% after first folding and subsequent drying. This stiffening causes a decrease of the finally achieved angle. Residue from the fabrication process found on the structures after folding is suspected to be the cause of the stiffening. © 2014 AIP Publishing LLC.
document
Kokorian, J.; Engelen, J. B. C.; De Vries, J.; Nazeer, H.; Woldering, L. A.; Abelmann, L.;
Thin Solid Films,
Volume 550, pp. 298 – 304, 2014. All Open Access, Green Open Access. DOI: 10.1016/j.tsf.2013.11.074
Keywords: ...
Atomic force microscopy; Crystal structure; Deposition; Elastic moduli; Surface roughness; X ray diffraction; Average surface roughness; C-axis orientations; Diamagnetic levitation; Peak-to-peak values; Polycrystalline textures; Template stripping; X-ray diffraction measurements; Young's Modulus; Bismuth.
Abstract: ...
In this paper we present a method to deposit thin films of bismuth with sub-nanometer surface roughness for application to diamagnetic levitation. Evaporated films of bismuth have a high surface roughness with peak to peak values in excess of 100 nm and average values on the order of 20 nm. We expose the smooth backside of the films using a template stripping method, resulting in a great reduction of the average surface roughness, to 0.8 nm. Atomic force microscope and X-ray diffraction measurements show that the films have a polycrystalline texture with preferential c-axis orientation. On the back side of the film, fine grains are grouped into larger clusters. Cantilever resonance shift measurements indicate that the Young's modulus of the films is on the order of 20 GPa. © 2013 Elsevier B.V.
document
Khalil, Islam S. M.; Abelmann, Leon; Misra, Sarthak;
IEEE Transactions on Magnetics,
Volume 50, Issue 10, 2014. All Open Access, Green Open Access. DOI: 10.1109/TMAG.2014.2323940
Keywords: ...
Disturbance compensation; Disturbance force; Magnetic; Micro manipulation; Model mismatch; Radio.
Abstract: ...
Magnetic systems have the potential to control the motion of microparticles and microrobots during targeted drug delivery. During their manipulation, a nominal magnetic force-current map is usually derived and used as a basis of the control system design. However, the inevitable mismatch between the nominal and actual force-current maps along with external disturbances affects the positioning accuracy of the motion control system. In this paper, we devise a control system that allows for the realization of the nominal magnetic force-current map and the point-to-point positioning of paramagnetic microparticles. This control is accomplished by estimating and rejecting the 2-D disturbance forces using an inner loop based on a disturbance force observer. In addition, an outer loop is utilized to achieve stable dynamics of the overall magnetic system. The control system is implemented on a magnetic system for controlling microparticles of paramagnetic material, which experience magnetic forces that are related to the gradient of the field-squared. We evaluate the performance of our control system by analyzing the transient- and steady-state characteristics of the controlled microparticle for two cases. The first case is done without estimating and rejecting the mismatch and the disturbance forces, whereas the second case is done while compensating for these disturbance forces. We do not only obtain 17% faster response during the transient state, but we are also able to achieve 23% higher positioning accuracy in the steady state for the second case (compensating disturbance forces). Although the focus of this paper is on the wireless magnetic-based control of paramagnetic microparticle, the presented control system is general and can be adapted to control microrobots. © 2014 IEEE.
document
Pichel, Marc P.; Hageman, Tijmen A. G.; Altmeyer, Matthias O.; Abelmann, Leon; Manz, Andreas;
conference, 2014.
Keywords: ...
Bacteria; Dynamic models; Magnetic field measurement; Magnetic fields; Magnetism; Alternating directions; Field strengths; Magnetic manipulation; Magnetotactic Bacteria; Microfluidic channel; Microfluidics.
Abstract: ...
We measured for the first time the U-turn trajectory of individual magneto-tactic bacteria (MTB) under reversal of the magnetic field, as a function of the field strength. The measurement was performed using shallow 5 micrometer deep microfluidic channels and a setup which allowed for magnetic fields with rapid alternating directions at varying magnitudes up to 60 mT. © 14CBMS.
document
Geerlings, J.; Sarajlic, E.; Berenschot, J. W.; Sanders, R. G. P.; Abelmann, L.; Tas, N. R.;
conference, 2014. DOI: 10.1109/MEMSYS.2014.6765583
Keywords: ...
Atomic force microscopy; Deposition; Drops; Electric fields; MEMS; Spray nozzles; Capillary nozzle; Droplet deposition; Electrospray deposition; External pressures; Fluorocarbon coatings; Fully integrated; High electric fields; Nano-scale aperture; Probes.
Abstract: ...
Electrospray deposition utilizes a high electric field to extract liquid droplets from a capillary nozzle. In this contribution we demonstrate non-contact droplet deposition by electrospray from atomic force microscopy (AFM) probes with a fully integrated microfluidic system, so called FluidFM probes. Electrospray experiments were performed using probes with a pyramidal tip with a sub-micron size aperture in a dedicated setup. The onset voltage as function of the gap between the probe tip and the substrate was measured and compared with a numerical model. Onset voltages in the range 360-410 V were found at 8.5 μm gap height. We observed a reduction in onset voltage with an increase in external pressure. Wetting of the outside of the tip could be reduced by applying a fluorocarbon coating. © 2014 IEEE.
document
Hatakeyama, K.; Sarajlic, E.; Siekman, M. H.; Jalabert, L.; Fujita, H.; Tas, N.; Abelmann, L.;
conference, 2014. All Open Access, Green Open Access. DOI: 10.1109/MEMSYS.2014.6765840
Keywords: ...
Atomic force microscopy; Electric properties; Infrared imaging; MEMS; Microelectrodes; Nanocantilevers; Nanowires; Scanning; Silicon nitride; Thermoanalysis; Corner lithography; Localized thermal analysis; Micro-thermal analysis; Of thermal phenomenon; Platinum nanowires; Resistive elements; Scanning thermal microscopy; Wafer scale fabrication; Probes.
Abstract: ...
Scanning Thermal Microscopy (SThM) and micro-thermal analysis allow the study of thermal phenomena at micro-and nanoscale. We present a novel scanning resistive probe aimed for thermal imaging and localized thermal analysis. The probe features an AFM cantilever with a sharp pyramidal tip. Metal nanowires are integrated at the inner edges of the pyramidal tip forming an electrical cross-junction at the apex. The nanometer-sized cross-junction, addressable through microelectrodes, can be utilized both as a local temperature sensor and a heater. We have fabricated a first prototype of the probe with a 150 μm long, 36 μm wide and 0.5 μm thick silicon nitride cantilever. Platinum nanowires, 300 nm wide and 100 nm thick, are successfully integrated using a wafer-scale fabrication process based on corner lithography. We have experimentally characterized electrical and thermal properties of the probe demonstrating its proper functioning. © 2014 IEEE.
document
Van Den Beld, Wesley T. E.; Cadena, Natalia L.; De Weerd, Eddy L.; Abelmann, Leon; Bomer, Johan G.; Van Den Berg, Albert; Eijkel, Jan C. T.;
conference, 2014.
Keywords: ...
Degrees of freedom (mechanics); Magnetism; Mathematical programming; Microchannels; Microspheres; Nickel alloys; Nonvolatile storage; Optical pumping; Pumps; Bidirectional pumping; Geometric programming; Magnetic microspheres; Permalloy; Rotating; Rotating magnetic fields; Rotation directions; Rotational frequency; Rotating disks.
Abstract: ...
We report geometrically programmable bidirectional pumping in microchannels using magnetic microspheres which rotate around magnetic disks under influence of an external rotating magnetic field. Geometric programming of the pumping direction is obtained by locating the magnetic disks on the inside or the outside curve of a microchannel as shown in Figure 1. A second degree of freedom in pumping direction is offered by the rotation direction of the external field. Pumping rate is controlled by the rotational frequency. © 14CBMS.
document
Krijnen, B.; Brouwer, D. M.; Abelmann, L.; Herder, J. L.;
conference, 2014.
Keywords: ...
Damping; Electrostatic actuators; Nanotechnology; Position control; Precision engineering; Q factor measurement; Comb drive; Control stability; Lower pressures; MEMS stage; Position sensors; Q-factors; Sensor response; Vacuum pressure; Thermal conductivity.
Abstract: ...
A flexure-based MEMS stage with electrostatic actuators and an integrated thermal position sensor was designed and fabricated. Both the thermal conductivity and the viscosity of air decrease for lower pressure. This was measured as a lower sensor response and higher Q-factor of the MEMS stage. For the first time, we considered the control stability of a MEMS stage as a function of decreasing pressure. We conclude that stable position control of the stage is possible for vacuum pressures down to 1 mbar.
document
Porter, Benjamin F.; Abelmann, Leon; Bhaskaran, Harish;
Nanotechnology,
Volume 24, Issue 40, 2013. All Open Access, Green Open Access. DOI: 10.1088/0957-4484/24/40/405304
Keywords: ...
Assembly; Electric fields; Gating and feeding; Surface plasmon resonance; Assembly process; Design parameters; Directed assembly; Nano-assemblies; Nano-manufacturing; Nonlinear poisson-boltzmann equation; Optimum design parameters; Single nanoparticle; Nanoparticles.
Abstract: ...
Techniques to reliably pick-and-place single nanoparticles into functional assemblies are required to incorporate exotic nanoparticles into standard electronic circuits. In this paper we explore the use of electric fields to drive and direct the assembly process, which has the advantage of being able to control the nano-assembly process at the single nanoparticle level. To achieve this, we design an electrostatic gating system, thus enabling a voltage-controllable nanoparticle picking technique. Simulating this system with the nonlinear Poisson-Boltzmann equation, we can successfully characterize the parameters required for single particle placement, the key being single particle selectivity, in effect designing a system that can achieve this controllably. We then present the optimum design parameters required for successful single nanoparticle placement at ambient temperature, an important requirement for nanomanufacturing processes. © 2013 IOP Publishing Ltd.
document
de Vries, Jeroen; Bolhuis, Thijs; Abelmann, Leon;
Journal of Applied Physics,
Volume 113, Issue 17, 2013. DOI: 10.1063/1.4801399
Keywords: ...
Alloys; Energy barriers; Magnetic materials; Multilayer films; Multilayers; Anomalous hall effects; Co/Pt multilayer; Ion beam etching; Laser interference lithography; Magnetic island; Magnetic layers; Switching field distribution; Thermal switching; Switching.
Abstract: ...
Two Co/Pt multilayer samples have been fabricated with a difference in the number of bilayers, leading to a total magnetic layer thickness of 3 nm and 20 nm. From these films, large arrays of magnetic islands have been patterned using laser interference lithography and ion beam etching. We have investigated the switching field distribution (SFD) of approximately 80 islands and thermal switching field distribution SFDT of individual islands of both samples using the anomalous Hall effect. We compare the results of these measurements with the (SFDT) of a previously investigated alloy with a magnetic layer thickness of 20 nm by comparing the results of over 1000 hysteresis loops of a single weak island and a single strong island. We found that that the energy barrier for the multilayer islands increases with increasing switching field, whereas it was previously found that the energy barrier for the alloy stays constant with varying switching fields. When comparing the two multilayer samples, we observe that the grain size, anisotropy, and switching field distribution are more or less independent on thickness, whereas the switching field at both 0 K and 300 K decreases with film thickness. © 2013 AIP Publishing LLC.
document
Engelen, Johan B. C.; Khatib, Mohammed G.; Abelmann, Leon; Elwenspoek, Miko C.;
Sensors and Actuators, A: Physical,
Volume 199, pp. 353 – 365, 2013. All Open Access, Green Open Access. DOI: 10.1016/j.sna.2013.05.020
Keywords: ...
Actuators; Analytical models; Electrodynamics; Electrostatics; Energy efficiency; Energy utilization; MEMS; Models; Probes; Virtual storage; Comb-drive actuator; Electrodynamic actuators; Electrostatic comb drives; Energy cost; Energy efficient; High-acceleration; Nano-positioner; Nanopositioners; Electrostatic actuators.
Abstract: ...
We investigate the energy consumption and seek-time performance of different actuator types for nanopositioners, with emphasis on their use in a parallel-probe-based data-storage system. Analytical models are derived to calculate the energy consumption and performance of electrodynamic (coil and permanent magnet) and comb-drive actuators. The equations are used to simulate the operation of probe-storage devices with these actuator types under a realistic file system load. The electrostatic comb-drive actuators are more energy efficient than the electrodynamic actuators, by an order of magnitude for slow movements and a factor of 2.5 for high-acceleration movements. Overall in a probe-storage device, comb-drive actuation is a factor of 3.3 more energy efficient than electrodynamic actuation, at the same level of performance. The analytical model presented in this work can be used to direct the optimization of nanopositioners and their use, for example, in terms of the data layout on the medium and the 'shutdown' policy of probe-storage devices. © 2013 Elsevier B.V.
document
Legrain, A.; Janson, T. G.; Berenschot, J. W.; Krijnen, G. J. M.; Abelmann, L.; Tas, N. R.;
conference, 2013. All Open Access, Green Open Access. DOI: 10.1109/NEMS.2013.6559787
Keywords: ...
Three dimensional; 3D microstructures; 3D Structure; Folded structures; Hydro-mechanical; On demands; Silicon nitride.
Abstract: ...
We present the controllable capillary folding of planar silicon nitride templates into 3D micro-structures by means of through-wafer liquid application. We demonstrate for the first time hydro-mechanical, repeatable, actuation of capillary folded structures via addition or retraction of water on demand. © 2013 IEEE.
document
Khalil, Islam S. M.; Pichel, Marc P.; Reefman, Bart A.; Sukas, Ozlem Sardan; Abelmann, Leon; Misra, Sarthak;
conference, 2013. All Open Access, Green Open Access. DOI: 10.1109/ICRA.2013.6631367
Keywords: ...
Bacteria; Closed loop control systems; Control systems; Fabrication; Channel wall; Channel widths; Closed-loop control; Magnetotactic Bacteria; Manipulation system; Positioning accuracy; Steady state; Robotics.
Abstract: ...
We demonstrate the closed-loop control of a magnetotactic bacterium (MTB), i.e., Magnetospirillum magnetotacticum, within a micro-fabricated maze using a magnetic-based manipulation system. The effect of the channel wall on the motion of the MTB is experimentally analyzed. This analysis is done by comparing the characteristics of the transient- and steady-states of the controlled MTB inside and outside a micro-fabricated maze. In this analysis, the magnetic dipole moment of our MTB is characterized using a motile technique (the u-turn technique), then used in the realization of a closed-loop control system. This control system allows the MTB to reach reference positions within a micro-fabricated maze with a channel width of 10 μm, at a velocity of 8 μm/s. Further, the control system positions the MTB within a region-of-convergence of 10 μm in diameter. Due to the effect of the channel wall, we observe that the velocity and the positioning accuracy of the MTB are decreased and increased by 71% and 44%, respectively. © 2013 IEEE.
document
Khalil, Islam S. M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G.; Abelmann, Leon; Misra, Sarthak;
conference, 2013. All Open Access, Green Open Access. DOI: 10.1109/EMBC.2013.6610745
Keywords: ...
Bacteria; Drug Delivery Systems; Ferric Compounds; Magnetic Fields; Magnetic Phenomena; Motion; Nanoparticles; Robotics; Bacteria; Drug delivery; Jets; Magnetic fields; Motion control; Nanoparticles; ferric ion; ferric oxide; nanoparticle; Drug delivery system; Iron oxide nanoparticle; Magnetic field gradient; Magnetic microrobots; Magnetotactic Bacteria; Motion controller; Point-to-point motion; Targeted drug delivery systems; bacterium; chemistry; drug delivery system; magnetic field; magnetism; metabolism; motion; procedures; robotics; ultrastructure; Nanomagnetics.
Abstract: ...
Development of targeted drug delivery systems using magnetic microrobots increases the therapeutic indices of drugs. These systems have to be incorporated with precise motion controllers. We demonstrate closed-loop motion control of microrobots under the influence of controlled magnetic fields. Point-to-point motion control of a cluster of iron oxide nanoparticles (diameter of 250 nm) is achieved by pulling the cluster towards a reference position using magnetic field gradients. Magnetotactic bacterium (MTB) is controlled by orienting the magnetic fields towards a reference position. MTB with membrane length of 5 μm moves towards the reference position using the propulsion force generated by its flagella. Similarly, self-propelled microjet with length of 50 μm is controlled by directing the microjet towards a reference position by external magnetic torque. The microjet moves along the field lines using the thrust force generated by the ejecting oxygen bubbles from one of its ends. Our control system positions the cluster of nanoparticles, an MTB and a microjet at an average velocity of 190 μm/s, 28 μm/s, 90 μm/s and within an average region-of-convergence of 132 μm, 40 μm, 235 μm, respectively. © 2013 IEEE.
document
Alink, Laurens; Groenland, J. P. J.; De Vries, Jeroen; Abelmann, Leon;
IEEE Transactions on Magnetics,
Volume 48, Issue 11, pp. 4574 – 4577, 2012. All Open Access, Green Open Access. DOI: 10.1109/TMAG.2012.2201138
Keywords: ...
Fourier series; Bit-patterned media; Channel modeling; Fourier-series expansion; High density; Jitter noise; Laser interference lithography; Magnetic island; Media noise; Model-based OPC; Jitter.
Abstract: ...
We measured the fluctuation in shape of magnetic islands in bit patterned media fabricated by laser interference lithography. This fluctuation can be accurately described by a model based on a Fourier series expansion of the perimeter of the islands. The model can be easily linked to amplitude and jitter noise. We show that the amplitude and jitter noise are in principle correlated, and the jitter noise increases with increasing island area. The correlation is small for media prepared by laser interference lithography, but expected to gain importance for high density bit patterned media. © 1965-2012 IEEE.
document
Koelmans, W. W.; Peters, T.; Berenschot, E.; De Boer, M. J.; Siekman, M. H.; Abelmann, L.;
Nanotechnology,
Volume 23, Issue 13, 2012. DOI: 10.1088/0957-4484/23/13/135301
Keywords: ...
Atomic force microscopy; Nanotips; Standards; AFM; Cantilever arrays; Contact modes; Convex corners; Data storage; Fabrication process; Free end; Load forces; Nano scale; Nano-manufacturing; Nanometres; Non-contact mode; Optical contact lithography; Probe-based; Process flows; Relative standard error; Resonance frequencies; Self-aligned; Sharp tip; Single-mask; Standard errors; Tip-sample distance; Tip-sample interaction; Wafer-scale; Nanocantilevers.
Abstract: ...
Cantilever arrays are employed to increase the throughput of imaging and manipulation at the nanoscale. We present a fabrication process to construct cantilever arrays with nanotips that show a uniform tipsample distance. Such uniformity is crucial, because in many applications the cantilevers do not feature individual tipsample spacing control. Uniform cantilever arrays lead to very similar tipsample interaction within an array, enable non-contact modes for arrays and give better control over the load force in contact modes. The developed process flow uses a single mask to define both tips and cantilevers. An additional mask is required for the back side etch. The tips are self-aligned in the convex corner at the free end of each cantilever. Although we use standard optical contact lithography, we show that the convex corner can be sharpened to a nanometre scale radius by an isotropic underetch step. The process is robust and wafer-scale. The resonance frequencies of the cantilevers within an array are shown to be highly uniform with a relative standard error of 0.26% or lower. The tipsample distance within an array of up to ten cantilevers is measured to have a standard error around 10nm. An imaging demonstration using the AFM shows that all cantilevers in the array have a sharp tip with a radius below 10nm. The process flow for the cantilever arrays finds application in probe-based nanolithography, probe-based data storage, nanomanufacturing and parallel scanning probe microscopy. © 2012 IOP Publishing Ltd.
document
Engelen, Johan B. C.; De Boer, Hylco; Beekman, Jethro G.; Fortgens, Laurens C.; De Graaf, Derk B.; Vocke, Sander; Abelmann, Leon;
Journal of Microelectromechanical Systems,
Volume 21, Issue 2, pp. 262 – 269, 2012. All Open Access, Green Open Access. DOI: 10.1109/JMEMS.2011.2179016
Keywords: ...
Electromechanical devices; MEMS; Musical instruments; Resonators; Ambient pressures; Audible frequency; Audio signal; Capacitive displacement sensors; Comb drive; Electrostatic tuning; Many resonators; Mass spring systems; Measurement results; MEMS technology; Micro-instrument; MP3 files; Quality factors; Sine-wave; Tunable resonators; Tuning ratio; Instruments.
Abstract: ...
The Micronium is a musical instrument fabricated from silicon using microelectromechanical system (MEMS) technology. It isto the best of our knowledgethe first musical micro-instrument fabricated using MEMS technology, where the actual sound is generated by mechanical microstructures. The Micronium consists of mass-spring systems that are designed to resonate at audible frequencies. Their displacement is measured by comb drives and is used as the audio signal to drive a loudspeaker. The instrument's sounds are pure sine waves. An extensive set of measurements of individual resonators is presented and discussed. Quality factor measurements at various ambient pressures show that an ambient pressure of 1 mbar results in a note duration of 1 s. The realized frequency deviates considerably from the designed resonator frequency. Measurement results of many resonators are shown to obtain understanding of this deviation. Initial experiments with electrostatic tuning using variable-gap comb drives show a tuning ratio of 5% maximum, depending on the resonator frequency. An audio recording of the instrument is included as a supplementary MP3 file. © 2012 IEEE.
document
Delalande, M.; De Vries, J.; Abelmann, L.; Lodder, J. C.;
Journal of Magnetism and Magnetic Materials,
Volume 324, Issue 7, pp. 1277 – 1280, 2012. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2011.09.037
Keywords: ...
Hall effect; Magnetic storage; Multilayers; Nucleation; Angular dependence; Anomalous Hall effects; Co/Pt multilayer; Depinning; Depinning fields; Domain nucleation; Easy axis; In-plane; Magnetic reversal; Nucleation field; Perpendicular anisotropy; Separate analysis; Magnetic domains.
Abstract: ...
Co/Pt multilayer dots with perpendicular anisotropy and with diameters of 250 and 350 nm were fabricated on top of a Hall cross configuration. The angular dependence of the magnetic reversal of the individual dot was investigated by Anomalous Hall effect measurements. At near in-plane angles (85° with the magnetic easy axis) the dot switches partially into a stable two-domain state. This allows for separate analysis of the angular dependence of both the field required for nucleation of a reversed domain, and the field required for depinning of the domain wall. The angular dependence of the depinning field fits accurately to a 1/cos(θ) behavior, whereas the angular dependence of the nucleation field shows a minimum close to 45°. The latter dependency can be accurately fitted to the modified Kondorsky model proposed by Schumacher [1]. © 2011 Elsevier B.V. All rights reserved.
document
Khalil, Islam S. M.; Metz, Roel M. P.; Abelmann, Leon; Misra, Sarthak;
conference, 2012. All Open Access, Green Open Access. DOI: 10.1109/IROS.2012.6386184
Keywords: ...
Elasticity; Intelligent systems; Nanosensors; Observability; Tissue; Applied current; Contact forces; Electronic complexity; Force estimation; Force sensing; Interaction forces; Magnetic system; Manipulation system; Micro particles; Physical force; Soft tissue; Wireless sensing; Estimation.
Abstract: ...
This work investigates the utilization of microparticles for the wireless sensing of interaction forces in magnetic-based manipulation systems. The proposed force estimation approach allows for using microparticles in sensing the interaction forces at hard-to-reach regions to avoid the mechanical and electronic complexities associated with physical force sensors. Based on the velocity of the microparticle and the applied currents at each of the electromagnets of the magnetic system, an interaction force observer is designed to estimate the contact forces between the microparticle and a soft-tissue simulant with different elasticities. Experimentally, a magnetic system is utilized to steer a microparticle towards a soft-tissue simulant to carry out force sensing. The experimental results show that forces in the range of nano-Newton can be estimated without nano-force sensors. The estimated interaction forces due to this contact can be used either in sensing and diagnosis applications, or in the realization of a force control system. © 2012 IEEE.
document
Van Den Beld, Wesley T. E.; De Weerd, Eddy L.; Abelmann, Leon; Bomer, Johan G.; Van Den Berg, Albert; Eijkel, Jan C. T.;
conference, 2012.
Keywords: ...
Biocompatibility; Magnetic fields; Microfluidics; Microspheres; Nickel alloys; Optical pumping; Pumps; Culture chambers; Magnetic microspheres; Microfluidic pumps; Permalloy; Recirculations; Rotating; Rotating magnetic fields; Superparamagnetic microspheres; Rotating disks.
Abstract: ...
We demonstrate a novel, flexible and biocompatible method to pump liquid through microchannels without the use of an external pump. The pumping principle is based on the rotation of superparamagnetic microspheres around permalloy disks, driven by an external in-plane rotating magnetic field. By placing the permalloy disks close to the edge of the channel, a net flow of 9 μm/s was generated in the middle of the channel. This pumping principle is especially suited for flow controlled medium recirculation in culture chambers, opening ways towards portable, on-chip closed cell culturing [1].
document
Khalil, Islam S. M.; Keuning, Jasper D.; Abelmann, Leon; Misra, Sarthak;
conference, 2012. All Open Access, Green Open Access. DOI: 10.1109/BioRob.2012.6290856
Keywords: ...
Biomagnetism; Motion control; Paramagnetism; Experimental verification; External magnetic field; Human bodies; Magnetic system; Micro-particles; Minimally invasive surgery; Modeling and control; Paramagnetic microparticles; Planning procedure; Position tracking errors; Potential field; Prototype system; Static and dynamic obstacles; Steady state; Motion planning.
Abstract: ...
This work investigates modeling and control of microparticles that could be guided inside the human body using external magnetic fields. Proposed areas of applications for these microparticles include but not limited to minimally invasive surgeries, diagnosis and sensing. The problem is formulated by modeling a magnetic prototype system which has been developed for the purpose of wireless motion control of microparticles. A control system is devised based on the way-point approach to control the navigation of the microparticles in a fluid. In addition, a path planning procedure based on a combination of the potential field and the A approaches is investigated in order to control the motion of the microparticles in the presence of static and dynamic obstacles. The experimental verification is conducted on a magnetic system designed for manipulation of microparticles. The experimental results demonstrates the motion control of microparticles with maximum steady state position tracking error of 8.6 μm within a 2.4 mm×1.8 mm workspace. © 2012 IEEE.
document
Burouni, Narges; Sarajlic, Edin; Siekman, Martin; Abelmann, Leon; Tas, Niels;
conference, 2012. All Open Access, Green Open Access. DOI: 10.1109/NEMS.2012.6196729
Keywords: ...
Atomic force microscopy; Electric properties; Infrared imaging; Nanocantilevers; Silicon nitride; Atomic force microscope (AFM); Corner lithography; Cross junction; Local temperature; Optical contact lithography; Scanning microscopy; Scanning probes; Silicon-nitride nanowires; Temperature changes; Tip apex; Nanowires.
Abstract: ...
We present a novel 3D nanowire pyramid as scanning microscopy probe for thermal imaging and atomic force microscopy. This probe is fabricated by standard micromachining and conventional optical contact lithography. The probe features an AFM-type cantilever with a sharp pyramidal tip composed of four freestanding silicon nitride nanowires with a diameter of 60 nm. The nanowires, which are made of silicon nitride coated by metal, form an electrical cross junction at the apex of the tip, addressable through the electrodes integrated on the cantilever. The cross junction on the tip apex can be utilized to produce heat and detect local temperature changes. Electrical and thermal properties of the probe were experimentally determined. The temperature changes in the nanowires due to Joule heating can be sensed by measuring the resistance of the nanowires. We employed the scanning probe in an atomic force microscope. © 2012 IEEE.
document
Nazeer, H.; Woldering, L. A.; Abelmann, L.; Nguyen, M. D.; Rijnders, G.; Elwenspoek, M. C.;
Microelectronic Engineering,
Volume 88, Issue 8, pp. 2345 – 2348, 2011. All Open Access, Green Open Access. DOI: 10.1016/j.mee.2011.01.028
Keywords: ...
Deposition; Elastic moduli; Elasticity; Finite element method; Nanocantilevers; Natural frequencies; Pulsed laser deposition; Silicon; Thin films; Vapor deposition; Cantilever; DRIE; PZT; Resonance frequency; Young's Modulus; Crystal orientation.
Abstract: ...
The Young's modulus of thin films can be determined by deposition on a micronsized Si cantilever and measuring the resonance frequency before and after deposition. The accuracy of the method depends strongly on the initial determination of the mechanical properties and dimensions of the cantilever. We discuss the orientation of the cantilever with respect to the Si crystal, and the inevitable undercut of the cantilever caused by process inaccuracies. By finite element modelling we show that the Young's modulus should be used instead of the analytical plate modulus approximation for the effective Young's modulus of Si cantilevers used in this work for both the 〈1 0 0〉 and 〈1 1 0〉 crystal orientation. Cantilever undercut can be corrected by variation of the cantilever length. As an example, the Young's modulus of PbZr0.52Ti0.48O3 (PZT) thin films deposited by pulsed laser deposition (PLD) was determined to be 99 GPa, with 1.4 GPa standard error. © 2011 Elsevier B.V. All rights reserved.
document
Nazeer, H.; Nguyen, M. D.; Woldering, L. A.; Abelmann, L.; Rijnders, G.; Elwenspoek, M. C.;
Journal of Micromechanics and Microengineering,
Volume 21, Issue 7, 2011. All Open Access, Green Open Access. DOI: 10.1088/0960-1317/21/7/074008
Keywords: ...
Deposition; Elastic moduli; Elasticity; Epitaxial films; Epitaxial growth; Nanocantilevers; Natural frequencies; Pulsed laser deposition; Semiconducting silicon compounds; Silicon wafers; Vapor deposition; Analytical relations; Crystal direction; Effective length; Epitaxial PZT; Epitaxially grown; Finite-element; Flexural rigidities; In-plane orientation; Micro-cantilevers; Over-etching; PZT; PZT thin film; Resonance frequencies; Standard errors; Young's Modulus; Pulsed lasers.
Abstract: ...
We determined the Young's modulus of pulsed laser deposited epitaxially grown PbZr0.52Ti0.48O3 (PZT) thin films on microcantilevers by measuring the difference in cantilever resonance frequency before and after deposition. By carefully optimizing the accuracy of this technique, we were able to show that the Young's modulus of PZT thin films deposited on silicon is dependent on the in-plane orientation, by using cantilevers oriented along the 〈1 1 0〉 and 〈1 0 0〉 silicon directions. Deposition of thin films on cantilevers affects their flexural rigidity and increases their mass, which results in a change in the resonance frequency. An analytical relation was developed to determine the effective Young's modulus of the PZT thin films from the shift in the resonance frequency of the cantilevers, measured both before and after the deposition. In addition, the appropriate effective Young's modulus valid for our cantilevers' dimensions was used in the calculations that were determined by a combined analytical and finite-element (FE) simulations approach. We took extra care to eliminate the errors in the determination of the effective Young's modulus of the PZT thin film, by accurately determining the dimensions of the cantilevers and by measuring many cantilevers of different lengths. Over-etching during the release of cantilevers from the handle wafer caused an undercut. Since this undercut cannot be avoided, the effective length was determined and used in the calculations. The Young's modulus of PZT, deposited by pulsed laser deposition, was determined to be 103.0 GPa with a standard error of ±1.4 GPa for the 〈1 1 0〉 crystal direction of silicon. For the 〈1 0 0〉 silicon direction, we measured 95.2 GPa with a standard error of ±2.0 GPa. © 2011 IOP Publishing Ltd.
document
Shao, Xiaoying; Alink, Laurens; Groenland, J. P. J.; Abelmann, Leon; Slump, Cornelis H.;
IEEE Transactions on Magnetics,
Volume 47, Issue 10, pp. 2559 – 2562, 2011. All Open Access, Green Open Access. DOI: 10.1109/TMAG.2011.2157668
Keywords: ...
Digital storage; Jitter; Magnetic storage; Magnetism; 2D coding; 2D-ISI; Bit-patterned media; Magnetic bit patterned medias; Patterned medias; Probe storage; Storage capacity; Two-dimensional coding; Intersymbol interference.
Abstract: ...
This paper presents a simple code to combat the two-dimensional inter-symbol interference (2D-ISI) effect that is present in data storage on magnetic bit patterned media. Whether the ISI effect is constructive or destructive depends on the surrounding bits. Therefore, we propose a simple 2D coding scheme to mitigate the ISI effect. With this 2D coding scheme in square patterned media, every 2-by-3 array has one redundant bit which has the opposite or same value of one of its adjacent bits. Compared to the 2D coding scheme in under the condition of the same areal density, the proposed 2D coding scheme increases the allowable bit-position jitter in square patterned media by 1% at a BER of 10-4; while it allows the effective storage capacity to be increased by around 5.5%. © 2011 IEEE.
document
Koelmans, W. W.; Sebastian, A.; Abelmann, L.; Despont, M.; Pozidis, H.;
Nanotechnology,
Volume 22, Issue 35, 2011. DOI: 10.1088/0957-4484/22/35/355706
Keywords: ...
Electric contacts; Nanotechnology; Platinum; Probes; Scanning probe microscopy; Silicides; Application area; Conductive probe; Data storage; Electrical contacts; Electrical sensing; Force modulation; Force modulation technique; Imaging experiments; Materials research; Nano scale; Platinum silicides; Probe-based; Semiconductor metrology; Tip wear; Electric properties.
Abstract: ...
Scanning probe microscopy employing conductive probes is a powerful tool for the investigation and modification of electrical properties at the nanoscale. Application areas include semiconductor metrology, probe-based data storage and materials research. Conductive probes can also be used to emulate nanoscale electrical contacts. However, unreliable electrical contact and tip wear have severely hampered the widespread usage of conductive probes for these applications. In this paper we introduce a force modulation technique for enhanced nanoscale electrical sensing using conductive probes. This technique results in lower friction, reduced tip wear and enhanced electrical contact quality. Experimental results using phase-change material stacks and platinum silicide conductive probes clearly demonstrate the efficacy of the proposed technique. Furthermore, conductive-mode imaging experiments on specially prepared platinum/carbon samples are presented to demonstrate the widespread applicability of this technique. © 2011 IOP Publishing Ltd.
document
Woldering, L{\' e}on A.; Abelmann, Leon; Elwenspoek, Miko C.;
Journal of Applied Physics,
Volume 110, Issue 4, 2011. All Open Access, Green Open Access. DOI: 10.1063/1.3624604
Keywords: ...
Crystals; Diamonds; Energy gap; Optical properties; Photonic band gap; Self assembly; Structures (built objects); Band gaps; Band structure calculation; Electronic systems; Hard spheres; Self-assembled; Silicon micromachining; Silicon particles; Crystal structure.
Abstract: ...
Recently, a silicon micromachining method to produce tetrahedral silicon particles was discovered. In this report we determine, using band structure calculations, the optical properties of diamond-lattice photonic crystals when assembled from such particles. We show that crystal structures built from silicon tetrahedra are expected to display small stop gaps. Wide photonic band gaps appear when truncated tetrahedral particles are used to build the photonic crystals. With truncated tetrahedral particles, a bandgap with a width of 23.6% can be achieved, which is more than twice as wide compared to band gaps in self-assembled diamond-lattices of hard-spheres. The width of the bandgap is insensitive to small deviations from the optimal amount of truncation. This work paves the way to a novel class of silicon diamond-lattice bandgap crystals that can be obtained through self-assembly. Such a self-assembly approach would allow for easy integration of these highly photonic crystals in existing silicon microfluidic and -electronic systems. © 2011 American Institute of Physics.
document
Abelmann, Leon;
Journal of Micromechanics and Microengineering,
Volume 21, Issue 7, 2011. All Open Access, Bronze Open Access. DOI: 10.1088/0960-1317/21/7/070201
document
Krijnen, B.; Hogervorst, R. P.; Van Dijk, J. W.; Engelen, J. B. C.; Woldering, L. A.; Brouwer, D. M.; Abelmann, L.; Soemers, H. M. J. R.;
Journal of Micromechanics and Microengineering,
Volume 21, Issue 7, 2011. All Open Access, Green Open Access. DOI: 10.1088/0960-1317/21/7/074007
Keywords: ...
Actuators; Electrostatic actuators; Capacitance model; Conductive heat transfer; Differential sensors; Displacement sensor; Doping concentration; Full-scale ranges; Operating temperature; Resistively heated; Sensor designs; Sensor resolution; Sensor sensitivity; Silicon structures; Single-mask; Thermal displacement sensors; Sensors.
Abstract: ...
This work presents a MEMS displacement sensor based on the conductive heat transfer of a resistively heated silicon structure towards an actuated stage parallel to the structure. This differential sensor can be easily incorporated into a silicon-on-insulator-based process, and fabricated within the same mask as electrostatic actuators and flexure-based stages. We discuss a lumped capacitance model to optimize the sensor sensitivity as a function of the doping concentration, the operating temperature, the heater length and width. We demonstrate various sensor designs. The typical sensor resolution is 2 nm within a bandwidth of 25 Hz at a full scale range of 110 μm. © 2011 IOP Publishing Ltd.
document
Gemelli, Marcellino; Abelmann, Leon; Engelen, Johan B. C.; Khatib, Mohammed G.; Koelmans, Wabe W.; Zaboronski, Oleg;
, 2011. DOI: 10.1007/978-3-642-14752-4_3
Abstract: ...
This chapter gives an overview of probe-based data storage research over the last three decades, encompassing all aspects of a probe recording system. Following the division found in all mechanically addressed storage systems, the different subsystems (media, read/write heads, positioning, data channel, and file system) will be discussed. In the media subsection various recording media will be treated, such as polymer based, phase change, ferroelectric and magnetic. In the probe array subsection various generations of thermal probes will be discussed, as well as examples of alternative write probes using currents, electric or magnetic fields, and different principles for data detection. Special attention is paid to parallel readout of probe arrays. In the positioning section, examples will be shown of electric and magnetic scanners, either precision engineered or realized by micromachining technologies, or combinations thereof. In the systems subsection the data channel will be discussed, including the read/write electronics circuitry, data detection, and coding algorithms. Special attention is paid to the writing strategy and considerations for probe-based storage file systems. © Springer-Verlag Berlin Heidelberg 2011.
document
Keuning, Jasper D.; De Vries, Jeroen; Abelmann, Leon; Misra, Sarthak;
conference, 2011. All Open Access, Green Open Access. DOI: 10.1109/IROS.2011.6048703
Keywords: ...
Finite element method; Intelligent robots; Machine design; Magnetic moments; Paramagnetic materials; Paramagnetism; Position control; Average diameter; Finite element method simulation; Image-based; Magnetic behavior; Magnetic control; Microscopic image; Paramagnetic microparticles; Vibrating sample magnetometer; Robotics.
Abstract: ...
This paper describes the design of a system for controlling the position of spherical paramagnetic microparticles that have an average diameter of 100 μm. The focus of this study lies in designing and implementing a system that uses microscopic images and electromagnets. Preliminary experiments have been done to verify the feasibility of the system to track and control the position of these particles. A vibrating sample magnetometer was used to determine the magnetic moment of the particles. Finite element method simulations were used to verify the magnetic behavior of the designed setup. The system was used to position the particles within 8.4μm of a setpoint, achieving speeds of up to 235μm s -1. We also demonstrated that the particle could follow a circular and a figure-eight path. © 2011 IEEE.
document
Sarajlic, E.; Siekman, M. H.; Fujita, H.; Abelmann, L.; Tas, N.;
conference, 2011. All Open Access, Green Open Access. DOI: 10.1109/MEMSYS.2011.5734480
Keywords: ...
Actuators; Atomic force microscopy; Electrostatic force; Friction; Mechanical engineering; Mechanics; MEMS; Monolithic integrated circuits; Nanocantilevers; Probes; Reactive ion etching; Scanning tunneling microscopy; AFM imaging; AFM probe; Circular plates; Electrostatic modulation; Flexural modes; Free end; Friction and wear; Monolithically integrated; New operation modes; Normal forces; Probe configuration; Scanning force microscopy; Sharp tip; Tip-sample contact; Tip-sample interaction; Electrostatic actuators.
Abstract: ...
A successful approach to drastically reduce or even completely eliminate friction and wear in scanning force microscopy is the use of electrostatic modulation of the normal force acting on the tip-sample contact. In this paper we have devised, fabricated and experimentally characterized a novel electrostatically actuated AFM probe. The probe consists of a flexible cantilever that has an electrostatic circular plate actuator with a built-in sharp tip monolithically integrated at its free end. This unique probe configuration will allow for the vibro-flexural mode operation in which vibration of the tip relative to the cantilever is generated and controlled by the integrated plate actuator, while the tip-sample interaction is resolved by deflection of the cantilever. We envision that this new operation mode will result in an efficient electrostatic force modulation, which in the end will enable us to control friction and wear during AFM imaging.
document
Khatib, Mohammed G.; Abelmann, Leon;
conference, 2011.
Keywords: ...
Energy efficiency; Virtual storage; Buffer capacity; Buffer sizes; Buffering requirements; Design spaces; Emerging technologies; Energy efficient; layout; MEMSDevices; Non-functional requirements; Optimal energy; Secondary storage; Storage devices; Streaming applications; Three orders of magnitude; Ultrahigh density; Design.
Abstract: ...
Emerging nanotechnology-based systems encounter new non-functional requirements. This work addresses MEMS storage, an emerging technology that promises ultrahigh density and energy-efficient storage devices. We study the buffering requirement of MEMS storage in streaming applications. We show that capacity and lifetime of a MEMS device dictate the buffer size most of the time. Our study shows that trading off 10% of the optimal energy saving of a MEMS device reduces its buffer capacity by up to three orders of magnitude. © 2011 EDAA.
document
Van Honschoten, J. W.; Legrain, A.; Berenschot, J. W.; Abelmann, L.; Tas, N. R.;
conference, 2011. DOI: 10.1109/MEMSYS.2011.5734418
Keywords: ...
Data storage equipment; Geometry; Lithography; Mechanical engineering; Mechanics; MEMS; Reactive ion etching; Silicon nitride; Basic elements; Capillary force; Corner lithography; Intersection plane; Micro assembly; Planar geometries; Silicon molds; Three-dimensional data; Three-dimensional shape; Three dimensional.
Abstract: ...
This paper presents the realization of micrometer sized silicon nitride tetrahedra with well-defined angles that are folded out of a planar geometry using capillary forces. The required specific three-dimensional shape is achieved by a well-defined folding sequence. Using the favorable properties of the recently developed corner lithography technique, a programmable stop hinge is micro-machined by etching specifically defined intersection planes of the silicon mold. Tetrahedra were successfully folded by capillarity validating this new technique. The demand for such a microstructure has become very large since it can form the essential basic element for future three-dimensional data storage systems.
document
Koelmans, W. W.; Van Honschoten, J.; De Vries, J.; Vettiger, P.; Abelmann, L.; Elwenspoek, M. C.;
Nanotechnology,
Volume 21, Issue 39, 2010. All Open Access, Green Open Access. DOI: 10.1088/0957-4484/21/39/395503
Keywords: ...
Electromagnetic Fields; Interferometry; Lab-On-A-Chip Devices; Nanotechnology; Optics and Photonics; Atomic force microscopy; Bandwidth; Natural frequencies; Array of cantilevers; Available bandwidth; Beam deflection; Biological sensing; Cantilever arrays; Data storage; Diode pairs; Dynamic modes; Multi frequency; Nano scale; Nanomechanical response; Optical beam deflection; Optical readout; Probe-based; Quality factors; Received signals; Resonant frequencies; Single lasers; article; electromagnetic field; instrumentation; interferometry; lab on a chip; methodology; nanotechnology; optics; Nanocantilevers.
Abstract: ...
Parallel frequency readout of an array of cantilevers is demonstrated using optical beam deflection with a single laser-diode pair. Multi-frequency addressing makes the individual nanomechanical response of each cantilever distinguishable within the received signal. Addressing is accomplished by exciting the array with the sum of all cantilever resonant frequencies. This technique requires considerably less hardware compared to other parallel optical readout techniques. Readout is demonstrated in beam deflection mode and interference mode. Many cantilevers can be readout in parallel, limited by the oscillators' quality factor and available bandwidth. The proposed technique facilitates parallelism in applications at the nano-scale, including probe-based data storage and biological sensing. © 2010 IOP Publishing Ltd.
document
Elwenspoek, Miko; Abelmann, Leon; Berenschot, Erwin; Van Honschoten, Joost; Jansen, Henri; Tas, Niels;
Journal of Micromechanics and Microengineering,
Volume 20, Issue 6, 2010. DOI: 10.1088/0960-1317/20/6/064001
Keywords: ...
Electric properties; Magnetic properties; Mechanical properties; Phase interfaces; Phase transitions; Stiction; Three dimensional; Disordered regions; Dynamic property; Electrical and magnetic property; First-order phase transitions; Kinetic process; Macroscopic systems; Mechanical interconnections; Static friction; Technological challenges; Three-dimensional structure; Self assembly.
Abstract: ...
We review aspects of static self-assembly with regard to the synthesizing of new types of three-dimensional materials made of specifically designed particles in the 100 nm to 10 μm range. Mechanical interconnection technologies based on static friction used in the assembly of macroscopic systems (such as screws and nails) are unsuitable for self-assembly. An analogy of self-assembly with first-order phase transitions is used to argue that self-assembly is a process requiring interfaces separating assembled and disordered regions. Available types of interaction are reviewed with emphasis on scaling. We discuss at some length how interaction and dynamic properties scale with respect to the particle size. Chains of particles seem to be of particular importance as they might form three-dimensional structures similar to proteins. These structures are constrained by the sequence of the particles and by their interactions between themselves and with the solvent. Using chains might provide a viable route to complex, inhomogeneous, supermaterials and systems. Kinetic processes, specifically nucleation and the relationship between self-assembly and thermodynamic phase transitions form a major part of this paper. Finally we review some applications of self-assembly, notably in MEMS, and put forward some ideas for the assembly of new types of (smart) supermaterials with interesting optical, mechanical, electrical and magnetic properties and describe some of the technological challenges we face when attempting to realize these materials and systems thereof. © 2010 IOP Publishing Ltd.
document
Alexandrou, M.; Nutter, P. W.; Delalande, M.; De Vries, J.; Hill, E. W.; Schedin, F.; Abelmann, L.; Thomson, T.;
Journal of Applied Physics,
Volume 108, Issue 4, 2010. All Open Access, Green Open Access. DOI: 10.1063/1.3475485
Keywords: ...
Finite element method; Hall effect; Magnetic field effects; Nanostructured materials; Nanostructures; Platinum; Three dimensional; Anomalous Hall effects; Bit-patterned media; Co/Pt multilayer; Cross structures; Magnetic nanostructures; Magnetic switching; Nano-islands; Numerical simulation studies; Output voltages; Patterned magnetic nanostructure; Seed layer; Spatial sensitivity; Switching behaviors; Switching field distribution; Theoretical study; Three dimensional finite element model; Switching.
Abstract: ...
Obtaining an accurate profile of the spatial sensitivity of Hall cross structures is crucial if such devices are to be used to analyze the switching behavior of magnetic nanostructures and determine the switching field distribution of bit patterned media. Here, we have used the anomalous Hall effect to investigate the switching of patterned Co/Pt multilayer magnetic nanoislands, where the Hall cross has been integrated into the Pt seed layer. Using the anomalous Hall output voltage we have observed the magnetic switching of individual islands, allowing the spatial sensitivity across a Hall cross structure to be determined. The experimental results agree well with numerical simulation studies, using a three-dimensional finite element model, and with existing theoretical studies, where the spatial sensitivity of two-dimensional Hall cross structures have been found numerically. © 2010 American Institute of Physics.
document
Abelmann, Leon; Tas, Niels; Berenschot, Erwin; Elwenspoek, Miko;
Micromachines,
Volume 1, Issue 1, pp. 1 – 18, 2010. All Open Access, Gold Open Access, Green Open Access. DOI: 10.3390/mi1010001
Keywords: ...
Crosstalk; Data storage equipment; Electric connectors; Memory architecture; MEMS; Self assembly; Silicon wafers; Associative network; Bit density; Corner lithography; Data storage; Electrical connection; Magnetic; Magnetic rings; Nano-sized elements; Non-volatile data; Non-volatile memories; Ring core; Self-assembled; Single crystal silicon; Non-volatile memory; Three dimensional.
Abstract: ...
The continuous increase in capacity of non-volatile data storage systems will lead to bit densities of one bit per atom in 2020. Beyond this point, capacity can be increased by moving into the third dimension. We propose to use self-assembly of nanosized elements, either as a loosely organised associative network or into a cross-point architecture. When using principles requiring electrical connection, we show the need for transistor-based cross-talk isolation. Cross-talk can be avoided by reusing the coincident current magnetic ring core memory architecture invented in 1953. We demonstrate that self-assembly of three-dimensional ring core memories is in principle possible by combining corner lithography and anisotropic etching into single crystal silicon. © 2010 by the authors. licensee Molecular Diversity Preservation International, Basel, Switzerland.
document
Engelen, Johan B. C.; Abelmann, Leon; Elwenspoek, Miko C.;
Journal of Micromechanics and Microengineering,
Volume 20, Issue 10, 2010. All Open Access, Green Open Access. DOI: 10.1088/0960-1317/20/10/105003
Keywords: ...
Drives; Electric potential; Optimization; Voltage regulators; Analytical expressions; Analytical solutions; Comb drive; Comb-drive fingers; Commonly used; Constant force; External loads; Finger shape; Finite element analysis; Force Curve; Graphical methods; Large displacements; Unit cells; Finite element method.
Abstract: ...
This work presents the analytical solution, finite-element analysis, realization and measurement of comb drives with finger shapes optimized for shock-resistant actuation. The available force for actuating an external load determines how large shock forces can be compensated for. The optimized finger shape provides much more available force than the standard straight finger shape, especially at large displacements. A graphical method is presented to determine whether stable voltage control is possible for a given available force curve. An analytical expression is presented for the finger shape that provides a constant large available force over the actuation range. The new finger shape is asymmetric, and the unit-cell width is equal to the unit-cell width of standard straight fingers that are commonly used, and can be used in all applications where a large force is required. Because the unit-cell width is not increased, straight fingers can be replaced by the new finger shape without changing the rest of the design. It is especially suited for shock-resistant positioning and for applications where a constant force is desired. © 2010 IOP Publishing Ltd.
document
Nguyen, M. D.; Nazeer, H.; Karakaya, K.; Pham, S. V.; Steenwelle, R.; Dekkers, M.; Abelmann, L.; Blank, D. H. A.; Rijnders, G.;
Journal of Micromechanics and Microengineering,
Volume 20, Issue 8, 2010. All Open Access, Green Open Access. DOI: 10.1088/0960-1317/20/8/085022
Keywords: ...
Atomic force microscopy; Computer simulation; Deposition; Electrodes; Finite element method; Lead; Mathematical models; MEMS; Microelectromechanical devices; Nanocantilevers; Natural frequencies; Piezoelectricity; Pulsed laser deposition; Semiconducting silicon compounds; Zirconium; Analytical model; Cantilever displacement; Conductive oxides; Finite element simulations; Initial bending; Laser doppler; Micro electro mechanical system; Oxide layer; Pb(Zr , Ti)O; Piezoelectric stack; Quality factors; Resonance frequencies; Silicon cantilever; Silicon-on-insulator substrates; Tip displacement; Vibrometers; White-light interferometer; Pulsed lasers.
Abstract: ...
This paper reports on the piezoelectric-microelectromechanical system micro-fabrication process and the behavior of piezoelectric stacks actuated silicon cantilevers. All oxide layers in the piezoelectric stacks, such as buffer-layer/bottom-electrode/film/top-electrode: YSZ/SrRuO3/Pb(Zr, Ti)3/SrRuO3, were grown epitaxially on the Si template of silicon-on-insulator substrates by pulsed laser deposition. By using an analytical model and finite element simulation, the initial bending of the cantilevers was calculated. These theoretical analyses are in good agreement with the experimental results which were determined using a white light interferometer. The dependences of the cantilever displacement, resonance frequency and quality factor on the cantilever geometry have been investigated using a laser-Doppler vibrometer. The tip displacement ranged from 0.03 to 0.42 μm V?1, whereas the resonance frequency and quality factor values changed from 1010 to 18.6 kHz and 614 to 174, respectively, for the cantilevers with lengths in the range of 100-800 μm. Furthermore, the effect of the conductive oxide electrodes on the stability of the piezoelectric displacement of the cantilevers has been studied. © 2010 IOP Publishing Ltd.
document
Engelen, J. B. C.; Delalande, M.; F{\`e}bre, A. J.; Bolhuis, T.; Shimatsu, T.; Kikuchi, N.; Abelmann, L.; Lodder, J. C.;
Nanotechnology,
Volume 21, Issue 3, 2010. All Open Access, Green Open Access. DOI: 10.1088/0957-4484/21/3/035703
Keywords: ...
Hall effect; Hysteresis; Hysteresis loops; Magnetic field effects; Magnetic materials; Platinum; Rotating machinery; Semiconductor quantum dots; Shock absorbers; Switching; Anomalous Hall effects; Arrhenius models; Co-Pt dot; Continuous films; Dot array; High field; High sensitivity; Large arrays; Laser interference lithography; Magnetic dot arrays; Magnetic reversal; Perpendicular magnetic anisotropy; Switching field; Switching field distribution; Thermally induced; Magnetic anisotropy.
Abstract: ...
Magnetic dot arrays with perpendicular magnetic anisotropy were fabricated by patterning Co80Pt20-alloy continuous films by means of laser interference lithography. As commonly seen in large dot arrays, there is a large difference in the switching field between dots. Here we investigate the origin of this large switching field distribution, by using the anomalous Hall effect (AHE). The high sensitivity of the AHE permits us to measure the magnetic reversal of individual dots in an array of 80 dots with a diameter of 180nm. By taking 1000 hysteresis loops we reveal the thermally induced switching field distribution SFDT of individual dots inside the array. The SFD T of the first and last switching dots were fitted to an Arrhenius model, and a clear difference in switching volume and magnetic anisotropy was observed between dots switching at low and high fields. © 2010 IOP Publishing Ltd.
document
Abelmann, Leon;
, 2010. DOI: 10.1016/B978-0-12-374413-5.00029-4
Abstract: ...
Magnetic force microscopy (MFM) is a scanning probe microscopy technique which images the magnetic stray field above flat specimens. This article is intended for researchers either working with MFM instrumentation or analysing the results measured by operators. We will discuss the theory behind the technique including the different measurement modes, image formation and techniques for interpreting the images. Next the MFM instrumentation will be discussed, including system aspects, feedback loops and available MFM tips. An extensive list of literature for further reading is provided. © 2010 Elsevier Ltd. All rights reserved.
document
Sarajlic, E.; Vermeer, R.; Delalande, M. Y.; Siekman, M. H.; Huijink, R.; Fujita, H.; Abelmann, L.;
conference, 2010. All Open Access, Green Open Access. DOI: 10.1109/MEMSYS.2010.5442498
Keywords: ...
Atomic force microscopy; Composite micromechanics; Conductive materials; Electric properties; Electric wire; Fabrication; Mechanical engineering; Mechanics; Micromachining; Nanocantilevers; Nanowires; Reactive ion etching; Scanning; Silicon nitride; Thermodynamic properties; AFM; Batch fabrication; Cross junction; Gold layer; Hall magnetometers; Local temperature; Magnetic imaging; Optical contact lithography; Probe tips; Scanning microscopy; Silicon-nitride nanowires; Thermal properties; Tip apex; Probes.
Abstract: ...
We present a process for batch fabrication of a novel scanning microscopy probe for thermal and magnetic imaging using standard micromachining and conventional optical contact lithography. The probe features an AFM-type cantilever with a sharp pyramidal tip composed of four freestanding silicon nitride nanowires coated by conductive material. The nanowires form an electrical cross junction at the apex of the tip, addressable through the electrodes integrated on the cantilever. The cross junction on the tip apex can be utilized to produce heat and detect local temperature changes or to serve as a miniaturized Hall magnetometer enabling, in principle, thermal and magnetic imaging by scanning the probe tip over a surface. We have successfully fabricated a first probe prototype with a nanowire tip composed of 140 nm thick and 11 μ m long silicon nitride wires metallized by 6 nm titan and 30 nm gold layers. We have experimentally characterized electrical and thermal properties of the probe demonstrating its proper functioning. ©2010 IEEE.
document
Engelen, Johan B. C.; Abelmann, Leon; Elwenspoek, Miko C.;
conference, 2010. All Open Access, Green Open Access. DOI: 10.1109/MEMSYS.2010.5442414
Keywords: ...
Mechanical engineering; Optimization; Reactive ion etching; Analytical expressions; Analytical solutions; Comb drive; Comb-drive fingers; External loads; Finger shape; Unit cells; Mechanics.
Abstract: ...
This work presents the analytical solution, realization and measurement of a comb drive with finger shapes optimized for shock-resistant actuation. The available force for actuating an external load determines how large shock forces can be compensated for. An analytical expression is presented for the finger shape that provides a constant large available force over the actuation range. The finger shape is asymmetric, resulting in a 20% smaller unit cell width compared to a symmetric shape. This finger shape provides 4 times more available force than the standard straight finger shape. ©2010 IEEE.
document
Engelen, J. B. C.; Rothuizen, H. E.; Drechsler, U.; Stutz, R.; Despont, M.; Abelmann, L.; Lantz, M. A.;
Microelectronic Engineering,
Volume 86, Issue 4-6, pp. 1230 – 1233, 2009. All Open Access, Green Open Access. DOI: 10.1016/j.mee.2008.11.032
Keywords: ...
Actuators; Aspect ratio; Data storage equipment; Drives; Electrostatics; Finite element method; MEMS; Microelectromechanical devices; Probes; Reactive ion etching; Scanning; Comb drive; Data storage applications; Data storages; Deep reactive ion etchings; DRIE; Finger shapes; Finite-element analysis (FEA); In planes; Out-of-plane directions; Probe storage; Prototype devices; Shock resistances; Electrostatic actuators.
Abstract: ...
In this work we describe the design, fabrication, and testing of a mass-balanced planar x/y-scanner designed for parallel-probe data storage applications. The scanner is actuated by comb drives, whose finger shape is improved using finite-element analysis to increase the force output. A mass-balancing concept is used for in-plane shock resistance; in the out-of-plane direction passive shock resistance is achieved using 1:40 aspect-ratio springs that are fabricated by deep reactive ion etching through the full thickness of a 400 μm wafer. A prototype device is presented and its performance is reported. © 2008 Elsevier B.V. All rights reserved.
document
Brombacher, Christoph; Saitner, Marc; Pfahler, Christian; Plettl, Alfred; Ziemann, Paul; Makarov, Denys; Assmann, Daniel; Siekman, Martin H.; Abelmann, Leon; Albrecht, Manfred;
Nanotechnology,
Volume 20, Issue 10, 2009. All Open Access, Green Open Access. DOI: 10.1088/0957-4484/20/10/105304
Keywords: ...
Anisotropy; Cobalt; Crystallization; Macromolecular Substances; Magnetics; Materials Testing; Membranes, Artificial; Molecular Conformation; Nanostructures; Nanotechnology; Particle Size; Platinum; Surface Properties; Magnetic anisotropy; Magnetic multilayers; Nanostructures; Plasma etching; Plasmas; Polystyrenes; nanomaterial; polystyrene; cobalt; nanomaterial; platinum; Co/pt multilayers; Domain nucleations; Domain-wall pinning; Etching time; Isotropic plasmas; Linear dependences; Magnetic nanostructures; Magnetic reversals; Packed arrays; Particle arrays; Particle locations; Particle systems; Perpendicular magnetic anisotropies; Perpendicular medias; Polystyrene particles; Single domains; Sub-50 nm; anisotropy; article; chemical reaction; film; magnetism; particle size; periodicity; priority journal; anisotropy; artificial membrane; chemistry; conformation; crystallization; macromolecule; materials testing; methodology; nanotechnology; surface property; ultrastructure; Magnetic bubbles.
Abstract: ...
Plasma etching of densely packed arrays of polystyrene particles leads to arrays of spherical nanostructures with adjustable diameters while keeping the periodicity fixed. A linear dependence between diameter of the particles and etching time was observed for particles down to sizes of sub-50nm. Subsequent deposition of Co/Pt multilayers with perpendicular magnetic anisotropy onto these patterns leads to an exchange-decoupled, single-domain magnetic nanostructure array surrounded by a continuous magnetic film. The magnetic reversal characteristic of the film-particle system is dominated by domain nucleation and domain wall pinning at the particle locations, creating a percolated perpendicular media system. © 2009 IOP Publishing Ltd.
document
Been, Auke J.; Folkertsma, Gerrit A.; Verputten, Hein H. J.; Bolhuis, Thijs; Abelmann, Leon;
Journal of Electron Microscopy,
Volume 58, Issue 4, pp. 251 – 252, 2009. All Open Access, Green Open Access. DOI: 10.1093/jmicro/dfp002
Keywords: ...
Electric lines; Electron microscopy; Timing circuits; % reductions; Disturbance; Electric circuitry; Electric power lines; Electrical power; Instrumentation; Magnetic-field; Power lines; Time varying; Time-varying magnetic fields; Magnetic fields.
Abstract: ...
Time-varying magnetic fields generated by electrical power lines in the laboratory can disturb electron microscope imaging. Modern microscopes require these fields to be below 10 nT 2. We calculated and measured magnetic fields from straight and twisted current-carrying wires, and show that without twisting, this value cannot be reached.
document
Engelen, J. B. C.; Lantz, M. A.; Rothuizen, H. E.; Abelmann, L.; Elwenspoek, M. C.;
conference, 2009. All Open Access, Green Open Access. DOI: 10.1109/SENSOR.2009.5285744
Keywords: ...
Actuators; Electrostatics; Finite element method; MEMS; Microelectromechanical devices; Microsystems; Piezoelectric transducers; Probes; Solid-state sensors; Comb drive; Comb fingers; Comb-drive actuator; Finger shape; Finite element analysis; Large-stroke; MEMS probes; Probe storage; Electrostatic actuators.
Abstract: ...
In this work we describe an electrostatic mass-balanced planar x/y-scanner, using an optimized comb finger shape, designed for parallel-probe storage applications. We show a new stepped comb finger shape design, that has superior force/displacement characteristics leading to a larger stroke at the same voltage and a larger available force compared to straight or tapered shapes. ©2009 IEEE.
document
Onoue, T.; Siekman, M.; Abelmann, L.; Lodder, J. C.;
Journal of Physics D: Applied Physics,
Volume 41, Issue 15, 2008. All Open Access, Green Open Access. DOI: 10.1088/0022-3727/41/15/155008
Keywords: ...
Crystallography; Magnetic anisotropy; Magnetic materials; Magnetic recording; Thick films; Capacitive currents; Current source; Cylindrical domains; Demagnetizing fields; External fields; Film-thickness; Heating processes; Magnetic probe recording; Perpendicular magnetic anisotropy; Perpendicular medium; Magnetic properties.
Abstract: ...
The possibility of magnetic probe recording into a continuous perpendicular medium is discussed. By applying a current from the tip to the medium, a very localized area can be heated and bits as small as 80 nm in diameter could be written. This value is close to the calculated minimum diameter of reversed cylindrical domains in our perpendicular medium. A current can be injected directly from the tip to the medium by means of a current source, or one can use capacitive currents. We prefer the first method, since the current, and therefore the heating process, can be controlled more precisely. The energy required to write a bit is in the order of 1 nJ. Calculations show that most of the heat is dissipated at the tip end. Demagnetizing fields of the surrounding material play an important role and are so strong that bits can be written without applying an external field. By decreasing the film thickness, the demagnetizing fields are reduced, and selective overwriting of previously written bits could be demonstrated. © 2008 IOP Publishing Ltd.
document
Le F{\`e}bre, A. J.; Abelmann, L.; Lodder, J. C.;
Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures,
Volume 26, Issue 2, pp. 724 – 729, 2008. All Open Access, Green Open Access. DOI: 10.1116/1.2894898
Keywords: ...
Annealing; Atomic force microscopy; Silicon; Titanium compounds; High resolution positioning; Nanometer distances; Field emission.
Abstract: ...
The dependence of the field emission effect on distance is applied for displacement sensing and high-resolution positioning. Silicon atomic force microscopy probes were used as a field emission source by applying voltages up to 400 V between this probe and a counter-electrode sample consisting of TiW sputtered on a silicon wafer. From current-voltage characteristics measured for distances varying from 50 to 950 nm, values for the field enhancement factor were determined which show a dependence on the electrode separation. This dependence can be correctly described by a model the authors developed using finite-element calculations and is determined by the emitter geometry and tip radius. Feedback to the probe position was used to maintain a constant current to apply this distance dependence for positioning. When increasing the applied voltage from 5 to 40 V for a constant current of 3 nA, the probe position is raised ∼90 nm. The nonlinear sensitivity of this positioning method is determined by the varying field enhancement and can be fitted by the same calculated model. Using feedback, the field emitter can be positioned with high lateral resolution and scanned over a conducting surface. Increasing the bias voltage from 3 to 50 V results in an increase in the emitter-sample distance and a decrease in lateral resolution. Damage to the scanned surface has to be prevented by using a current-limiting resistor and by annealing the probe and sample under ultra high vacuum conditions before use. © 2008 American Vacuum Society.
document
Hartel, Pieter H.; Abelmann, Leon; Khatib, Mohammed G.;
conference, 2008.
Keywords: ...
Magnetization; Virtual storage; Local heating; Magnetic dots; Magnetic medium; Patterned medias; Probe storage; Read/write operations; Storage systems; Tamper-evident; Magnetic storage.
Abstract: ...
We propose a tamper-evident storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual magnetic dots. We report on measurements showing that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. We discuss the main issues of designing a tamper-evident storage device and file system using the properties of the medium. © 2015 OSA - The Optical Society. All rights reserved.
document
Murillo, R.; Siekman, M. H.; Bolhuis, T.; Abelmann, L.; Lodder, J. C.;
Microsystem Technologies,
Volume 13, Issue 2, pp. 177 – 180, 2007. DOI: 10.1007/s00542-006-0143-x
Keywords: ...
Cobalt compounds; Magnetic anisotropy; Magnetometers; Optical switches; Thermodynamic stability; Torque; Energy barriers; Magnetic force microscopy; Nanodots; Switching field distribution; Nanostructured materials.
Abstract: ...
The thermal dependence and distribution of the switching fields of arrays of magnetic Co50Ni50/Pt nanodots has been studied. These dots, with a diameter of 90 nm, are arranged in a hexagonal pattern with a periodicity of 300 nm. Field-dependent magnetic force microscopy was used to measure the switching field distribution of the array, which was found to range from 80 to 192 kA/m, a value which is confirmed by vibrating sample magnetometer measurements. Additionally, the temperature dependence on the collective behaviour of the switching fields of the array has been investigated. The energy barrier at zero field was estimated to have a value in between 1.8×10-19 and 2.1×10-19 J. Combining this value with the effective anisotropy determined by torque measurements, the switching volume can be estimated to lie in between 1.2×103 and 1.4×103 nm3. © Springer-Verlag 2007.
document
Alonso-Gonz{\'a}lez, Pablo; Gonz{\'a}lez, Luisa; Gonz{\'a}lez, Yolanda; Fuster, David; Fern{\'a}ndez-Mart{\'i}nez, Iv{\'a}n; Martín-S{\'a}nchez, Javier; Abelmann, Leon;
Nanotechnology,
Volume 18, Issue 35, 2007. All Open Access, Green Open Access. DOI: 10.1088/0957-4484/18/35/355302
Keywords: ...
Etching; Indium arsenide; Lithography; Molecular beam epitaxy; Oxidation; Semiconductor growth; Substrates; ozone; quantum dot; article; chemical binding; geometry; laser; optical resolution; oxidation; priority journal; quality control; ultraviolet radiation; Laser interference lithography; Optical quality; Patterning technologies; Semiconductor quantum dots.
Abstract: ...
This work presents a selective ultraviolet (UV)-ozone oxidation-chemical etching process that has been used, in combination with laser interference lithography (LIL), for the preparation of GaAs patterned substrates. Further molecular beam epitaxy (MBE) growth of InAs results in ordered InAs/GaAs quantum dot (QD) arrays with high optical quality from the first layer of QDs formed on the patterned substrate. The main result is the development of a patterning technology that allows the engineering of customized geometrical displays of QDs with the same optical quality as those formed spontaneously on flat non-patterned substrates. © IOP Publishing Ltd.
document
Luttge, R.; Van Wolferen, H. A. G. M.; Abelmann, L.;
Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures,
Volume 25, Issue 6, pp. 2476 – 2480, 2007. All Open Access, Green Open Access. DOI: 10.1116/1.2800328
Keywords: ...
Interferometry; Lithography; Thin Films; Laser interferometry; Photoresists; Thin films; Chemical amplification; Chemical amplified resist; Lloyd mirror; Nanoarrays; Nanolithography.
Abstract: ...
The authors report on the progress of laser interference lithography at 266 nm laser wavelength with a chemical amplified resist containing a polyvinyl derivate dissolved in propylene glycol monoethyl ether ester. A continuous-wave deep-UV source combined with a Lloyd mirror is a simple and useful tool for the fabrication of nanoscale periodic structures generally called nanoarrays. Aiming for a robust pattern transfer technique to fabricate nanoarrays into magnetic materials, the authors investigated the utility of a chemical amplification positive tone resist, despite the relatively high theoretical resolution limit of 133 nm (λ2) pattern period for the laser source used. Taking advantage of this new type of resist, the authors demonstrated for the first time the fabrication of an 18 Gbit in.2 dot pattern on a platinum thin film. © 2007 American Vacuum Society.
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
Physica B: Condensed Matter,
Volume 387, Issue 1-2, pp. 328 – 332, 2007. DOI: 10.1016/j.physb.2006.04.028
Keywords: ...
Cobalt compounds; Magnetic fields; Multilayers; Optical resolving power; Scanning tunneling microscopy; Full-width half-maximum (FWHM); High-density magnetic recording; Magnetic force microscopy (MFM); Magnetic recording.
Abstract: ...
A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. Magnetic marks were formed by a scanning tunneling microscopy (STM)-based thermal magnetic mechanism on a perpendicular CoNi/Pt multilayered film. Magnetic force microscopy (MFM) was applied to display those marks. The MFM signal is dependent of the lift-height during MFM scanning: smaller lift-height leads to higher resolution of the MFM image and a double-peak signal line, while higher lift-height leads to lower resolution and a single-peak signal line. Theoretical calculation of the magnetic field from the mark was executed. It agrees well with experiments, and demonstrates the method of mark size measurement in perpendicular media: full-width half-maximum (FWHM) of the measured MFM signal. © 2006 Elsevier B.V. All rights reserved.
document
Groenland, J. P. J.; Abelmann, L.;
IEEE Transactions on Magnetics,
Volume 43, Issue 6, pp. 2307 – 2309, 2007. All Open Access, Green Open Access. DOI: 10.1109/TMAG.2007.893137
Keywords: ...
Bit error rate; Computer simulation; Magnetic force microscopy; Pattern matching; Redundancy; Signal encoding; Intertrack interference; Patterned media; Perpendicular magnetic recording; Two-dimensional coding; Magnetic recording.
Abstract: ...
The effect of intertrack intersymbol interference in a magnetic patterned medium is studied. A 2-D channel code is proposed, dedicated to perpendicularly magnetized media without soft underlayer, which exhibit read pulses showing overshoot. Read pulse shapes were investigated using a magnetic-force microscope tip scanning the patterned medium row by row. To test different codes, a bit-detection simulation program was developed to generate large amounts of data on which bit error rates can be measured. Application of the 2-D channel code, which implies recording of particular dot positions with fixed bits ("ones," "zeros") resulted in the elimination of 2-D worst case bit patterns and a subsequent reduction of detected-bit errors. The accompanying redundancy of 22% is inevitable for this type of 2-D code. © 2007 IEEE.
document
Le F{\`e}bre, A. J.; Siekman, M.; Abelmann, L.; Lodder, J. C.;
conference, 2007. All Open Access, Green Open Access. DOI: 10.1109/SENSOR.2007.4300644
Keywords: ...
Actuators; Atomic force microscopy; Field emission; Microscopic examination; Microsystems; Scanning probe microscopy; Sensors; Transducers; Constant Current; Displacement sensing; Electrode gaps; Experimental data; Exponential relation; Field emission currents; Field emission sources; Field emissions; Fowler-Nordheim equations; International conferences; Linear regime; Nanometer resolutions; Nm resolution; Probe recording; Probe tips; Sensor; Sensor performances; Solid-state sensors; Imaging techniques.
Abstract: ...
Field emission is used as a displacement sensing method, exploiting the exponential relation between field emission current and electrode gap. Atomic force microscopy (AFM) probes have been used as field emission source to measure I/V characteristics which were found to correspond well to theory. The field emission sensor was operated in a more linear regime by using feedback on the position of the probe in order to maintain a constant current. The sensitivity of the sensor for displacement was found to be 0.26 V/nm at a range of ∼100 nm. From the experimental data, typical parameters for the Fowler-Nordheim equation were deduced and used to model the sensor performance. The measurements confirm that field emission can be applied to sense the distance between a probe tip and sample with <20 nm resolution. ©2007 IEEE.
document
F{\`e}bre, Alexander; Abelmann, L.; Lodder, J. C.;
conference, 2007. All Open Access, Green Open Access. DOI: 10.1109/IVNC.2007.4481005
document
F{\`e}bre, A. J.; Luttge, R.; Abelmann, L.; Lodder, J. C.;
conference, 2007. All Open Access, Gold Open Access, Green Open Access. DOI: 10.1088/1742-6596/61/1/135
Abstract: ...
An integrated method using field-emission to control the tip-sample distance for non-contact magnetic probe recording is presented, adopting the exponential relation between current and electric field as feedback. I/V characteristics that correspond well to field emission theory are measured using a probe coated with a 100 nm conductive diamond layer. By using feedback to control the tip-sample distance at constant current, the distance was increased by 2.8 nm per volt applied bias. The method was tested by scanning a probe coated with 20 nm chromium over a conducting nanopatterned sample, at bias voltages of 0.5V, 5.0V and 50.0V. The measurements confirm that field emission can be applied to control the tip-sample distance, with sufficient resolution and current stability for magnetic probe recording. © 2007 IOP Publishing Ltd.
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
Journal of Applied Physics,
Volume 99, Issue 2, 2006. DOI: 10.1063/1.2162272
Keywords: ...
Cobalt alloys; Computer simulation; Magnetic domains; Magnetic field effects; Mathematical models; Multilayers; Platinum; Scanning tunneling microscopy; Thin films; Threshold voltage; Field emission current; Heating sources; Probe based storage systems; Synthesized models; Magnetic recording.
Abstract: ...
A method of heat-assisted magnetic recording potentially suitable for probe-based storage systems is characterized. In this work, field-emission current from a scanning tunneling microscope tip is used as the heating source. Pulse voltages of 2-7 V were applied to a CoNiPt multilayered film. During heating, various external magnetic fields were applied. Experimental results show that a positive magnetic field increases mark size while a negative field decreases mark size, compared to the case of writing without an external field in which an average mark size of 170 nm was achieved. In addition, a positive field reduces the threshold voltage of writing as well. A synthesized model is built to quantitatively simulate the experimental results. It includes the model of emission current, heat transfer, and dynamics of magnetic domains in the film. Simulation results show that the calculated mark size in various cases is consistent with experimental results. Based on this model, we will be able to figure out the proposals to achieve small marks for the goal of 1 Tbit in.2 recording density. © 2006 American Institute of Physics.
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
Physica B: Condensed Matter,
Volume 381, Issue 1-2, pp. 204 – 208, 2006. DOI: 10.1016/j.physb.2006.01.007
Keywords: ...
Field emission cathodes; Magnetic recording; Multilayers; Substrates; Thermal conductivity; Bare silicon; High density magnetic recording; Multilayered film; Oxidized silicon; Heat transfer.
Abstract: ...
A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 3-7 V with a duration of 500 ns were applied to a CoNi/Pt multilayered film which is fabricated on a bare silicon and oxidized silicon, respectively. For both substrates, write threshold voltage of 4 V was observed. Above threshold, mark size was 170 and 260 nm for the films on bare silicon and oxidized silicon, respectively. A model of 2-D heat transfer in a multilayered film structure was applied and the mark size difference was explained by the thermal conductivity of the substrate. © 2006 Elsevier B.V. All rights reserved.
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
Journal of Physics D: Applied Physics,
Volume 39, Issue 12, pp. 2485 – 2487, 2006. DOI: 10.1088/0022-3727/39/12/002
Keywords: ...
Electric potential; Heat treatment; Magnetic films; Magnetic recording; Magnetic storage; Magnetic probe recording; Multilayered film; Pulse voltages; Ultra-high recording density; Multilayers.
Abstract: ...
A method of heat-assisted magnetic recording potentially suitable for probe-based storage systems is characterized. Field emission current from a scanning tunnelling microscope tip is used as the heating source. Pulse voltages of 5 V were applied to a granular CoNi/Pt multilayered film. Experimental results show that an average mark size of 90-120 nm was achieved with the minimum of 70 nm. A model of dynamic domain formation is built to quantitatively explain the experimental results. It agrees with experiments. Based on this model, we will be able to figure out the proposals to achieve small marks for ultra-high recording density. © 2006 IOP Publishing Ltd.
document
Davelaar, G. G.; Abelmann, L.;
Synthese,
Volume 153, Issue 3, pp. 457 – 458, 2006. DOI: 10.1007/s11229-006-9095-z
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
Journal of Applied Physics,
Volume 100, Issue 5, 2006. DOI: 10.1063/1.2336505
Keywords: ...
Cobalt alloys; Coercive force; Magnetic domains; Magnetic recording; Platinum; Scanning tunneling microscopy; Field emission current; Magnetic domain dynamics; Recording density; Thermal-magnetically formed marks; Multilayers.
Abstract: ...
We characterized a method of heat-assisted magnetic recording, which is potentially suitable for probe-based storage systems. The field emission current from a scanning tunneling microscope tip was used as the heating source. Various pulse voltages were applied to two types of CoNi/Pt multilayered films: one is strongly coupled with low coercivity, and the other is weakly coupled with high coercivity. Experimental results show that marks achieved in strongly coupled medium are larger than that in granular one. An external magnetic field was then applied to those marks. For weak fields (lower than the coercivity of the medium) the size of marks changes distinctly in the strongly coupled medium but not in the granular one. A model of magnetic domain dynamics is built to quantitatively explain the experimental results. It agrees with experiments. Based on this model, we will be able to figure out the proposals to achieve small marks for ultrahigh recording density. © 2006 American Institute of Physics.
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
Journal of Magnetism and Magnetic Materials,
Volume 305, Issue 1, pp. 16 – 23, 2006. DOI: 10.1016/j.jmmm.2005.11.022
Keywords: ...
Cobalt compounds; Magnetic recording; Platinum; Probes; Scanning tunneling microscopy; Silicon; Substrates; Heat assisted magnetic recording (HAMR); High density perpendicular recording; Probe recording; Multilayers.
Abstract: ...
A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2-7 V were applied to a CoNi/Pt multilayered film fabricated on either bare silicon or oxidized silicon substrates. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm on the film fabricated on bare silicon substrate when the pulse voltage is above a threshold voltage. The mark size becomes 260 nm when they are written on the identical film fabricated on an oxidized silicon substrate. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. A synthesized model, which contains the calculation of the emission current, the simulation of heat transfer during heating, and the study of magnetic domain formation, was introduced to explain experimental results. The simulation agrees well with the experiments. © 2005 Elsevier B.V. All rights reserved.
document
Onoue, T.; Siekman, M. H.; Abelmann, L.; Lodder, J. C.;
Journal of Magnetism and Magnetic Materials,
Volume 287, Issue SPEC. ISS., pp. 501 – 506, 2005. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2004.10.083
Keywords: ...
Coercive force; Demagnetization; Electric currents; Magnetic field effects; Magnetic films; Magnetic storage; Multilayers; Heat assist; Magnetic force microscopy; Probe recording; Magnetic recording.
Abstract: ...
Heat-assisted magnetic probe recording on a CoNi/Pt multilayered film is demonstrated by delivering a current through a magnetic force microscopy tip into the recording medium, in combination with an external magnetic field. Without local heating by the probe, no bits could be written because the external field exceeds a level that demagnetizes the medium in its entirety due to local variations in the coercivity of the medium. In contrast, magnetic bits were successfully written by the heat-assisted magnetic probe recording into a saturated medium even if there was no external field, because of the demagnetization field from the surrounding of the heated area. A magnetic bit as small as 80 nm in diameter was obtained by this method. © 2004 Elsevier B.V. All rights reserved.
document
Murillo, R.; Van Wolferen, H. A.; Abelmann, L.; Lodder, J. C.;
Microelectronic Engineering,
Volume 78-79, Issue 1-4, pp. 260 – 265, 2005. All Open Access, Green Open Access. DOI: 10.1016/j.mee.2005.01.004
Keywords: ...
Antireflection coatings; Data storage equipment; Ion beams; Lithography; Magnetic materials; Photoresists; Spin coating; Laser interference lithography; Magnetic dots; Nanodots; Patterned media; Nanostructured materials.
Abstract: ...
A method of fabrication of patterned magnetic nanodots by means of laser interference lithography is presented. This method includes the use of a diluted positive photoresist, and modifications in the etching angle and acceleration voltage of the ion beam etching process. Vertical standing waves were suppressed by using a high exposure dose (supra-exposure) instead of an antireflective coating. Field dependent magnetic force microscopy was used to measure the switching field distribution, which was found to range from 80 to 192 kA/m. © 2005 Published by Elsevier B.V.
document
Craus, C. B.; Onoue, T.; Ramst{\"o}ck, K.; Geerts, W. G. M. A.; Siekman, M. H.; Abelmann, L.; Lodder, J. C.;
Journal of Physics D: Applied Physics,
Volume 38, Issue 3, pp. 363 – 370, 2005. DOI: 10.1088/0022-3727/38/3/002
Keywords: ...
Atomic force microscopy; Computer simulation; Etching; Ion beams; Magnetic anisotropy; Magnetic domains; Magnetoresistance; Microelectromechanical devices; Parameter estimation; Photolithography; Demagnetizing energy; Ion beam etching; Micromagnetic simulations; Scanning probe microscopy (SPM); Magnetic recording.
Abstract: ...
We present our results on the development of magnetic sensors for application in magnetic probe recording. Successful writing experiments on a magnetic medium with perpendicular anisotropy show that magnetic domains of 130 nm can be reversed in a heat-assisted process. For reading purposes we propose a magnetoresistive sensor. The optimization of the shape of the sensor was performed using micromagnetic simulations with the requirement that the sensor has to be capable of both read and write operations. At this stage, the experimental realization of the sensor was carried out at a wafer-base level. The fabrication technique consists of a combination of optical lithography and focused ion beam etching.
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
conference, 2005.
document
Dao, N.; Kikuchi, N.; Abelmann, L.; Lodder, J. C.;
conference, 2005. All Open Access, Green Open Access. DOI: 10.1109/intmag.2005.1464357
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
IEEE Transactions on Magnetics,
Volume 40, Issue 4 II, pp. 2549 – 2551, 2004. DOI: 10.1109/TMAG.2004.830220
Keywords: ...
Diffusion; Field emission cathodes; Magnetic recording; Magnetic storage; Probes; Scanning tunneling microscopy; Size determination; Thermal effects; Threshold voltage; Field emission; High-density recording; Prolate spheroidal coordinates; Multilayers.
Abstract: ...
A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, Held emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2-7 V with a duration of 500 ns were applied to a CoNi/Pt multilayered film. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm when the pulse voltage is above a threshold voltage. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. The emission area of our tip-sample system derived from an analytic expression for field emission current is approximately equal to the mark size, and is largely independent of pulse voltage. This emission area is large compared to lateral heat diffusion in the film. Thus higher applied voltages lead to higher peak temperatures in the model of the write process, but the mark diameter remains relatively unchanged.
document
Onoue, T.; Siekman, M. H.; Abelmann, L.; Lodder, J. C.;
Journal of Magnetism and Magnetic Materials,
Volume 272-276, Issue III, pp. 2317 – 2318, 2004. All Open Access, Green Open Access. DOI: 10.1016/j.jmmm.2003.12.940
Keywords: ...
Cobalt compounds; Magnetic amplifiers; Magnetic couplings; Magnetic materials; Magnetization; Multilayers; Probes; Thin films; CoNi/Pt multilayer; Exchange coupling; Magnetic bits; Probe recording; Magnetic recording.
Abstract: ...
Reversed single magnetic bits of 130nm in diameter were successfully written in a CoNi/Pt multilayered film by means of magnetic probe recording. A weak exchange coupled layer deposited onto a stronger exchange coupled layer effectively induces a local magnetic reversal, which results in the formation of small and stable magnetic bits. © 2003 Elsevier B.V. All rights reserved.
document
Zhang, Li; Bain, James A.; Zhu, Jian-Gang; Abelmann, Leon; Onoue, Takahiro;
conference, 2004. DOI: 10.1115/nano2004-46057
Keywords: ...
Approximation theory; Electric potential; Magnetooptical effects; Metallic films; Scanning tunneling microscopy; Superparamagnetism; Surface tension; Emission current; Heat-assisted magnetic recording (HAMR); Magnetic probe recording; Pulse voltage; Magnetic recording.
Abstract: ...
A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. The tip is made of Ir/Pt alloy. Pulse voltages of 3-7 V with a duration of 500ns were applied to a CoNi/Pt multilayered film. Written by a blunt tip (radius 1000nm), marks are formed with a nearly uniform mark size of 170nm when the pulse voltage is above 4 V. While sharp tip (radius 50 nm) writing achieves no mark. The emission area of our tipsample system derived from an analytic expression for field emission current is approximately equal to the mark size, and is largely independent of pulse voltage. For the blunt tip, the emission region is almost the same as the mark size. While for the sharp tip, the initially formed mark is too small, so that the domain wall surface tension shrinks the mark and it crashes finally. Copyright © 2004 by ASME.
document
Saito, Hitoshi; Van den Bos, Arnout; Abelmann, Leon; Lodder, J. Cock;
IEEE Transactions on Magnetics,
Volume 39, Issue 5 II, pp. 3447 – 3449, 2003. All Open Access, Green Open Access. DOI: 10.1109/TMAG.2003.816178
Keywords: ...
Computer simulation; Magnetization; Optical resolving power; Thermal noise; Magnetic force microscopy (MFM); Magnetic domains.
Abstract: ...
The transfer functions of tips with various sharpened tip ends were calculated and the resolution of these tips was estimated by considering the resolution limit due to thermal noise at room temperature. The tip having an ellipsoidal tip end (ellipsoidal tip) is found to be a suitable candidate for high-resolution magnetic force microscopy. Sharpening of the flat tip end makes zero signal frequencies disappear for tips with ellipticities larger than tan 45°. The sensitivity shows a maximum around an ellipticity of tan 80°. The ellipsoidal tip shows a much smaller tip thickness dependence compared to the tip having a flat tip end because only the tip end mainly contributes to signals in case of the ellipsoidal tip.
document
Abelmann, L.; Bolhuis, T.; Hoexum, A. M.; Krijnen, G. J. M.; Lodder, J. C.;
IEE Proceedings: Science, Measurement and Technology,
Volume 150, Issue 5, pp. 218 – 221, 2003. All Open Access, Green Open Access. DOI: 10.1049/ip-smt:20030693
Keywords: ...
Cellular arrays; Computer architecture; Data recording; Magnetic heads; Microactuators; Robots; Storage allocation (computer); Mass data storage system architecture; Storage robots; Data storage equipment.
Abstract: ...
The authors propose a concept in mass data storage system architecture, in which thousands of read/write heads, storage robots or StoBots move independently over a large, flat storage medium. This concept, which has not been previously proposed, offers new degrees of freedom in data storage systems design, which could lead to a superior performance over conventional systems such as hard disks and tape. The impact of different file system architectures on the access time and data-rate of the StoBot drive is investigated.
document
Saito, H.; Van Den Bos, A. G.; Abelmann, L.; Lodder, J. C.;
conference, 2003. All Open Access, Green Open Access. DOI: 10.1109/INTMAG.2003.1230602
Keywords: ...
Artificial intelligence; Magnetic domains; Magnetic films; Magnetic force microscopy; Magnetic recording; Frequency; Magnetic force; Perpendicular magnetic recording; Shape; Signal resolution; Magnetism.
Abstract: ...
In this paper, we calculate MFM signals for tips with various tip-end shapes and discuss the effect of tip sharpening of MFM sensitivity and resolution. © 2003 IEEE.
document
Phillips, G. N.; Siekman, M.; Abelmann, L.; Lodder, J. C.;
Applied Physics Letters,
Volume 81, Issue 5, pp. 865 – 867, 2002. All Open Access, Green Open Access. DOI: 10.1063/1.1497434
Keywords: ...
Aspect ratio; Atomic force microscopy; Cobalt; Focused ion beams; Ions; Magnetic force microscopy; Magnetism; Thermal evaporation; Ambient conditions; Atomic force microscopes; Co films; CoNi/Pt multilayer; Focused ion beam milling; High aspect ratio; High resolution; Magnetic elements; Magnetic images; Magnetic shape; Nm resolution; Magnetic anisotropy.
Abstract: ...
Atomic force microscope tips coated by the thermal evaporation of a magnetic 30 nm thick Co film have been modified by focused ion beam milling with Ga+ ions to produce tips suitable for magnetic force microscopy. Such tips possess a planar magnetic element with high magnetic shape anisotropy, an extremely high aspect ratio of greater than 30:1, and an end radius of less than 25 nm. These tips have been used in a commercial atomic force microscope under ambient conditions to obtain 30 nm resolution magnetic images of an established CoNi/Pt multilayer reference sample. © 2002 American Institute of Physics.
document
Phillips, Gavin N.; Eisenberg, Martin; Draaisma, Eddie A.; Abelmann, Leon; Lodder, J. Cock;
IEEE Transactions on Magnetics,
Volume 38, Issue 5 II, pp. 3528 – 3535, 2002. All Open Access, Green Open Access. DOI: 10.1109/TMAG.2002.802743
Keywords: ...
Finite element method; Ion implantation; Magnetic flux; Magnetic recording; Magnetic tape; Magnetoresistance; Microscopic examination; Ion beam trimming; Magnetic microscopy; Magnetic heads.
Abstract: ...
Thin-film yoke-type magnetoresistive (MR) tape heads with eight channels have been used for scanning magnetoresistance microscopy. The NiFe read flux guides of the channels have been trimmed down from 12 μm to widths varying between 5 μm and 100 nm by focused ion-beam milling with Ga + ions. The tape-bearing surface of the milled regions has been reconstructed in situ by the local deposition of Pt. Tracks with a minimum bit length of 1 μm have been written on Co-Ni-O metal evaporated tape and Co-γ-Fe 2O 3 particulate tape with trimmed and untrimmed write channels and have been successfully imaged with all the trimmed read channels. A linear decrease in readback voltage across the MR sensor is observed for channels possessing flux guides trimmed down to 2 μm, in agreement with finite-element modeling of the trimmed heads. The severe attenuation in readback voltage observed for flux guides trimmed below 2 μm is attributed to a combination of micromagnetic effects. Additionally, damage to the NiFe from Ga + ion implantation may make a minor contribution to the loss in sensor performance. A 65% drop in readback voltage is observed for a channel possessing a flux guide that was trimmed by 98.3% to 200 nm.
document
Sindhu, S.; Haast, M. A. M.; Ramst{\"o}ck, K.; Abelmann, L.; Lodder, J. C.;
Journal of Magnetism and Magnetic Materials,
Volume 238, Issue 2-3, pp. 246 – 251, 2002. DOI: 10.1016/S0304-8853(01)00919-2
Keywords: ...
Cobalt compounds; Computer simulation; Electron energy levels; Laser applications; Lithography; Magnetic domains; Magnetic hysteresis; Magnetic storage; Magnetization; Switching; Laser interference lithography; Magnetic dots; Multilayers.
Abstract: ...
The domain structure and the switching field of Co50Ni50/Pt multilayer dots, prepared by laser interference lithography, were micromagnetically simulated. The simulations were carried out with a three-dimensional simulation package, optimized for large-scale problems. The single-domain state is the lowest energy state for dots with a diameter below 75nm. The switching field was computed by using suitable minimization techniques, and was used to analyze the effect of size, dot shape and edge defects. © 2002 Elsevier Science B.V. All rights reserved.
document
Van Den Bos, A. G.; Heskamp, I. R.; Siekman, M. H.; Abelmann, L.; Lodder, J. C.;
conference, 2002. All Open Access, Green Open Access. DOI: 10.1109/INTMAG.2002.1000809
Keywords: ...
Atomic force microscopy; Magnetic materials; Nanocantilevers; Probes; Silicon nitride; Batch fabrication; Higher resolution; Imaging process; Magnetic coatings; Magnetic recording systems; Manufacturing process; Measurement tools; Silicon micromachining; Magnetism.
Abstract: ...
With the current rate of increase in areal density of magnetic recording systems, todays resolution of MFM needs to be improved in order to remain useful as a measurement tool. The resolution of MFM is amongst others determined by the geometry of the magnetic tip, which for commercial probes consists of a thin magnetic coating deposited on a pyramidal Si AFM tip. Analysis of the imaging process shows that the shape of these tips is not ideal. For higher resolution, the tip must be shaped as an elongated bar with a flat front end. In this contribution we present a completely new MFM cantilever, the CantiClever, which is not derived from traditional AFM probes but optimized for MFM. Our design incorporates the cantilever and the magnetic tip in a single manufacturing process with the use of silicon micromachining techniques, allowing for batch fabrication of the probes. We realise the ideal tip shape by deposition of the magnetic material (Co) on the side of a free hanging silicon nitride layer. ©2002 IEEE.
document
Abelmann, Leon; Bolhuis, Thijs; Lodder, Cock;
conference, 2002. All Open Access, Green Open Access. DOI: 10.1109/INTMAG.2002.1000887
Keywords: ...
Data transfer; Hard disk storage; Probes; Data density; Data storage; Hard Disk Drive; High capacity; Probe recording; Storage area; Total performance; Underlying cause; Digital storage.
Abstract: ...
The progress in data-rate and access time of the hard disk drive has not kept pace with the tremendous increase in data density. This has a deteriorating effect on the total performance of desktop computer systems. The underlying cause of this problem is that only a few heads are responsible for all data transfer. It would be better if the number of heads scales proportionally with the capacity. Probe recording systems, which use thousands of heads in parallel, might offer a solution. The disadvantage of the probe array architectures that have been suggested up to now, is that the total storage area, and therefore the capacity, is low. For areas of several tens of cm2, the probe array would be difficult to realize and too expensive. In order to reach high capacity, we suggest to break up the array into smaller subarrays of about 10 probes each, and distribute them over a large area (a tile). This requires that the sub-arrays have actuators with which they can move over the medium surface, like miniature data storage robots, or StoBots, with dimensions of a few 100 μm. ©2002 IEEE.
document
Phillips, Gavin N.; Siekman, Martin; Abelmann, Leon; Lodder, Cock;
conference, 2002. All Open Access, Green Open Access. DOI: 10.1109/INTMAG.2002.1000808
Keywords: ...
Cobalt; Magnetic force microscopy; Magnetism; Focused ion beam milling; Focussed ion beams; High resolution; Higher resolution; Magnetic elements; Magnetic force microscopies (MFM); Magnetic media; Magnetic stray fields; Ion beams.
Abstract: ...
Magnetic force microscopy (MFM) is well established for imaging surface magnetic stray fields. With commercial microscopes and magnetic tips, images with 50 nm resolution are quite routine; however, obtaining higher resolutions is experimentally more demanding. Higher resolution is required for imaging patterned magnetic elements and the latest magnetic media where bit lengths are less than 40 nm. Sub-30 nm resolution images of a 20 bilayer Co50Ni50/Pt thin film have been obtained using Si tips coated with Co and modified by focused ion beam (FIB) milling. Imaging was performed at room temperature, in air, with a Digital Instruments D13100 MFM in tapping/lift mode. ©2002 IEEE.
document
Phillips, G. N.; Eisenberg, M.; Persat, N.; Draaisma, E. A.; Abelmann, L.; Lodder, J. C.;
Sensors and Actuators, A: Physical,
Volume 91, Issue 1-2, pp. 34 – 38, 2001. DOI: 10.1016/S0924-4247(01)00476-9
Keywords: ...
Computer simulation; Finite element method; Gallium; Ion beams; Magnetic recording; Magnetic tape; Magnetoresistance; Microscopic examination; Milling (machining); Probes; Focused ion beam milling; Magnetic recording heads; Magnetoresistive heads; Read back voltage; Read flux guides; Scanning magnetoresistance microscopy; Voltage drop; Magnetic heads.
Abstract: ...
Scanning magneto-resistance microscopy has been performed with thin film yoke-type magneto-resistive tape heads possessing eight channels. The read flux guides of these channels have been trimmed down from 24 μm to widths varying between 5.5 μm and 148 nm by focused ion beam milling with Ga+ ions. Tracks written on ME tape with an untrimmed write channel have been successfully imaged with all the trimmed channels. A significant attenuation (>5%) of read-back voltage across the MR sensor is only observed for channels possessing flux guides trimmed by 77% to 5.5 μm. A 52% (∼6 dB) drop in read-back voltage is observed for a channel possessing a flux guide trimmed by 99.4% to 148 nm.
document
Carley, L. Richard; Bain, James A.; Fedder, Gary K.; Greve, David W.; Guillou, David F.; Lu, Michael S. C.; Mukherjee, Tamal; Santhanam, Suresh; Abelmann, Leon; Min, Seungook;
Journal of Applied Physics,
Volume 87, Issue 9 III, pp. 6680 – 6685, 2000. All Open Access, Green Open Access. DOI: 10.1063/1.372807
Abstract: ...
This article describes an approach for implementing a complete computer system (CPU, RAM, I/O, and nonvolatile mass memory) on a single integrated-circuit substrate (a chip) - hence, the name "single-chip computer." The approach presented combines advances in the field of microelectromechanical systems (MEMS) and micromagnetics with traditional low-cost very-large-scale integrated circuit style parallel lithographic manufacturing. The primary barrier to the creation of a computer on a chip is the incorporation of a high-capacity [many gigabytes (GB)] re-writable nonvolatile memory (in today's terminology, a disk drive) into an integrated circuit (IC) manufacturing process. This article presents the following design example: a MEMS-based magnetic memory that can store over 2 GB of data in 2 cm2 of die area and whose fabrication is compatible with a standard IC manufacturing process. © 2000 American Institute of Physics.
document
Litvinov, Dmitri; Chomko, Roman M.; Abelmann, Leon; Ramst{\"o}ck, Klaus; Chen, GaLane; Khizroev, Sakhrat;
IEEE Transactions on Magnetics,
Volume 36, Issue 5 I, pp. 2483 – 2485, 2000. All Open Access, Green Open Access. DOI: 10.1109/20.908481
Keywords: ...
Cobalt alloys; Magnetic flux; Magnetic permeability; Magnetic thin films; Soft underlayers; Soft magnetic materials.
Abstract: ...
The micromagnetic properties of a soft underlayer in perpendicular media are studied. It is shown that stray fields from a recording layer can substantially modify magnetic properties of soft underlayer material. The degree of modification is determined by the characteristic bit size in the recording layer and by the soft underlayer material magnetic characteristics. It is found that there exists a thin layer within a soft underlayer with reduced permeability. The effects of the presence of such a reduced permeability region within a soft underlayer on both reading and writing processes are discussed.
document
Abelmann, Leon; Khizroev, Sakhrat K.; Litvinov, Dmitri; Zhu, Jian-Gang; Bain, James A.; Kryder, Mark H.; Ramst{\"o}ck, Klaus; Lodder, Cock;
Journal of Applied Physics,
Volume 87, Issue 9 III, pp. 6636 – 6638, 2000. DOI: 10.1063/1.372795
Abstract: ...
In single-pole heads with a pole tip cross section trimmed down to 100X200 nm by focused ion beam, the remanence of the head becomes nonzero if the pole length is too high. Large-scale three-dimensional micromagnetic simulations are performed to understand this effect, and to calculate the critical length of the pole as a function of the pole tip cross section. © 2000 American Institute of Physics.
document
Abelmann, Leon; Zhu, Jian-Gang; Bain, James A.; Ramst{\"o}ck, Klaus; Lodder, Cock;
Journal of Applied Physics,
Volume 87, Issue 9 II, pp. 5538 – 5540, 2000. All Open Access, Green Open Access. DOI: 10.1063/1.373397
Abstract: ...
Large scale 3D micromagnetic simulations are performed on single pole read heads with pole tip cross sections of 45×45 and 100×200 nm. It is shown that tips with these dimensions have a much higher output than predicted by an analytical theory using the reciprocity theorem. The larger of these tips still behaves in a relatively soft manner and has an output waveform shape very close to the one predicted by the analytical model. The response of the small tip however is hysteretic. © 2000 American Institute of Physics.
document
Litvinov, D.; Chomko, R. M.; Abelmann, L.; Ramst{\"o}ck, K.; Khizroev, S.;
Digests of the Intermag Conference,
pp. BB – 2, 2000. All Open Access, Green Open Access. DOI: 10.1109/INTMAG.2000.871878
Abstract: ...
Micromagnetic simulations and experimental studies were made to account for the physics of a soft underlayer. The existence of a reduced permeability region was observed. Results of the study suggest a set of criteria for a proper choice of the materials parameters, such as anisotropy, exchange length, and saturation magnetization to minimize the effect.
document
Litvinov, D.; Chomko, R. M.; Abelmann, L.; Ramstock, K.; Khizroev, S.;
conference, 2000.
Keywords: ...
Computer simulation; Magnetic anisotropy; Magnetic domains; Magnetic fields; Magnetic flux; Magnetic permeability; Magnetization; Soft magnetic materials; Superparamagnetism; Thermodynamic stability; Areal bit density; Domain wall thickness; Micromagnetics; Magnetic recording.
Abstract: ...
Micromagnetic simulations and experimental studies were made to account for the physics of a soft underlayer. The existence of a reduced permeability region was observed. Results of the study suggest a set of criteria for a proper choice of the materials parameters, such as anisotropy, exchange length, and saturation magnetization to minimize the effect.
document
Bolhuis, T.; Abelmann, L.; Lodder, J. C.; Samwel, E. O.;
Journal of Magnetism and Magnetic Materials,
Volume 193, Issue 1-3, pp. 332 – 336, 1999. All Open Access, Green Open Access. DOI: 10.1016/S0304-8853(98)00451-X
Keywords: ...
Calibration; Crosstalk; Curve fitting; Demagnetization; Electric coils; Magnetic tape; Magnetic thin films; Magnetization; Vectors; Vibrating sample magnetometers (VSM); Magnetometers.
Abstract: ...
A calibration method for the biaxial vector Vibrating Sample Magnetometer (VSM) is proposed to reduce the so-called 'cross talk' error, often observed during angular measurements on magnetic thin films. The coil system of the biaxial vector VSM consists of two sets of coils, one for each of the two co-ordinate axes. The method takes into account that each coil set is sensitive to all components of the magnetisation vector and moreover that the sensitivity to the components parallel and perpendicular to the film plane can be different. A correction for demagnetisation should be used to compensate the fact that the sample used for the calibration cannot be fully saturated with an applied field at angles close to the normal of the film plane. Curve-fitting on the sensitivity curves is used to reduce noise. These procedures result in a calibration which reduces the cross talk by a factor 4-8 depending on the coil configuration and the size and shape of the samples used. © 1999 Elsevier Science B.V. All rights reserved.
document
Vellekoop, S. J. L.; Abelmann, L.; Porthun, S.; Lodder, J. C.; Miles, J. J.;
Journal of Magnetism and Magnetic Materials,
Volume 193, Issue 1-3, pp. 474 – 478, 1999. All Open Access, Green Open Access. DOI: 10.1016/S0304-8853(98)00524-1
Keywords: ...
Computational methods; Magnetic heads; Magnetism; Mathematical models; Microscopic examination; Transfer functions; Force transfer functions (FTF); Fourier space; Magnetic force microscopy (MFM); Micromagnetism; Playback transfer functions (PTF); Magnetic recording.
Abstract: ...
Magnetic force microscopy has proven to be a suitable tool for analysis of high-density magnetic recording materials. Comparison of the MFM image of a written signal with the actual read-back signal of the recording system can give valuable insight in the recording properties of both heads and media. In a first order approach one can calculate a 'signal' by plotting the line integral over the track width along the track direction (Glijer et al., IEEE Trans. Magn. 32 (1996) 3557). The method however does not take into account the spatial frequency dependence of the transfer functions of both the MFM and the readback system. For instance the gap width of the head (limiting the high frequency signals) and the finite length of the MFM tip (limiting the sensitivity for low frequencies) are completely disregarded (Porthun et al., J. Magn. Magn. Mater. 182 (1998) 238). This type of problem involving spatial frequencies can be very elegantly solved in the Fourier space. The response of the MFM is described by the force transfer function (FTF) as introduced by (Porthun et al. (J. Magn. Magn. Mater. 182 (1998) 238) and Hug et al. (J. Appl. Phys. 83 (1998) 5609), which describes the relation between the MFM signal and the sample stray field at the height of the tip. From this stray field an 'effective surface charge distribution' can be calculated, by means of the field transfer function (HTF). The same function HTF can be used to calculate the stray field at the height of the head. From this stray field the playback voltage can be calculated, resulting in the playback transfer function (PTF). In order to do this the Karlquist model had to be extended to three dimensions. © 1999 Elsevier Science B.V. All rights reserved.
document
Haast, M. A. M.; Heskamp, I. R.; Abelmann, L.; Lodder, J. C.; Popma, Th. J. A.;
Journal of Magnetism and Magnetic Materials,
Volume 193, Issue 1-3, pp. 511 – 514, 1999. All Open Access, Green Open Access. DOI: 10.1016/S0304-8853(98)00484-3
Keywords: ...
Arrays; Cobalt alloys; Coercive force; Etching; Ion beams; Laser applications; Lithography; Magnetic anisotropy; Magnetic hysteresis; Magnetic recording; Metallic superlattices; Platinum; Laser interference lithography; Magnetic force microscopy (MFM); Polar Kerr magnetometry; Torque magnetometry; Magnetic films.
Abstract: ...
Co50Ni50/Pt multilayers with perpendicular magnetic anisotropy have been patterned into single and multi domain dots by laser interference lithography and ion beam etching. The samples (typically 1 × 1 cm2) have been characterized by VSM, polar Kerr Magnetometry, Torque Magnetometry and Magnetic Force Microscopy. The relation between coercivity, anisotropy and dot size is discussed. Also the rotational hysteresis loss of single and multi domain dots is reported. © 1999 Elsevier Science B.V. All rights reserved.
document
Bijker, M. D.; Abelmann, L.; Lodder, J. C.; Popma, Th. J. A.;
Journal of Magnetism and Magnetic Materials,
Volume 193, Issue 1-3, pp. 357 – 361, 1999. All Open Access, Green Open Access. DOI: 10.1016/S0304-8853(98)00455-7
Keywords: ...
Deposition; Evaporation; Fluorescence; Magnetic recording; Microstructure; Oxygen; Transmission electron microscopy; X ray fluorescence (XRF) analysis; Magnetic tape.
Abstract: ...
The role of oxygen will be discussed in comparing some experimental tapes to a commercial Hi8ME tape. Both the oxygen flow and the deposition rate play an important role in understanding how oxygen is incorporated in the film during the evaporation process. © 1999 Elsevier Science B.V. All rights reserved.
document
Hug, Hans J.; Stiefel, B.; Van Schendel, P. J. A.; Moser, A.; Hofer, R.; Martin, S.; G{\" u}ntherodt, H.-J.; Porthun, Steffen; Abelmann, Leon; Lodder, J. C.; Bochi, Gabriel; O'Handley, R. C.;
Journal of Applied Physics,
Volume 83, Issue 11, pp. 5609 – 5620, 1998. All Open Access, Green Open Access. DOI: 10.1063/1.367412
Abstract: ...
We present a transfer-function approach to calculate the force on a magnetic force microscope tip and the stray field due to a perpendicularly magnetized medium having an arbitrary magnetization pattern. Under certain conditions, it is possible to calculate the magnetization pattern from the measured force data. We apply this transfer function theory to quantitatively simulate magnetic force microscopy data acquired on a CoNi/Pt multilayer and on an epitaxially grown Cu/Ni/Cu/Si(001) magnetic thin film. The method described here serves as an excellent basis for (i) the definition of the condition for achieving maximum resolution in a specific experiment, (ii) the differences of force and force z-derivative imaging, (iii) the artificial distinction between domain and domain wall contrast, and finally (iv) the influence of various tip shapes on image content. © 1998 American Institute of Physics.
document
Vellekoop, Bas; Abelmann, Leon; Porthun, Steffen; Lodder, Cock;
Journal of Magnetism and Magnetic Materials,
Volume 190, Issue 1-2, pp. 148 – 151, 1998. DOI: 10.1016/S0304-8853(98)00280-7
Keywords: ...
Computational methods; Magnetic fields; Magnetic force microscopy (MFM); Magnetic variables measurement.
Abstract: ...
In this contribution it is proven mathematically that it is in principle impossible to determine the magnetic charge distribution inside a magnetic material by a method which measures the stray field outside the sample, such as magnetic force microscopy (MFM). A general source of stray field, Eσ, is defined and it is shown that different solutions can be found for Eσ that result in the same stray field. It is also shown how both a perpendicular and a longitudinal medium can be described with the same Eσ. Using the equations for stray field, resulting from Eσ, it is also proven that performing the same MFM measurement at different scanning heights does not provide any new information on the stray field for sample; from a measurement at one (constant) height, the stray field at all other heights can be calculated. Moreover, the component of the field parallel to the same plane can be obtained from a measurement of the field component perpendicular to the sample plane. © 1998 Elsevier Science B.V. All rights reserved.
document
Porthun, S.; Abelmann, L.; Vellekoop, S. J. L.; Lodder, J. C.; Hug, H. J.;
Applied Physics A: Materials Science and Processing,
Volume 66, Issue SUPPL. 1, pp. S1185–S1189, 1998. DOI: 10.1007/s003390051323
Keywords: ...
Magnetic fields; Magnetic force microscopy; Magnetic recording; Detector noise; High-lateral resolution; Lateral resolution; Recording media; Ultrahigh density; Magnetic heads.
Abstract: ...
Magnetic force microscopy (MFM) plays an important role in magnetic recording research. It is not only suited for the study of magnetic heads and recording media, but is also a possible technique for ultrahigh-density bit writing. One of the key properties of this technique is the geometric simplicity of the magnetic field-detecting element-which makes it suitable for reaching very high lateral resolution. Starting from the tip transfer function (TTF), as derived in [1], a minimum detectable wavelength will be used as a measure for the lateral resolution of the instrument. This minimum detectable wavelength will determine the detector noise level in the instrument's configuration. The model of the minimum detectable wavelength is then used to optimize the tip-sample configuration geometrically as well as magnetically. © 1998 Springer-Verlag.
document
Abelmann, Leon; Porthun, Steffen; Haast, Marc; Lodder, Cock; Moser, Andreas; Best, Margaret E.; Van Schendel, Pieter J. A.; Stiefel, Bruno; Hug, Hans J.; Heydon, Greg P.; Farley, Andrew; Hoon, Steve R.; Pfaffelhuber, Thomas; Proksch, Roger; Babcock, Ken;
Journal of Magnetism and Magnetic Materials,
Volume 190, Issue 1-2, pp. 135 – 147, 1998. All Open Access, Green Open Access. DOI: 10.1016/S0304-8853(98)00281-9
Keywords: ...
Cobalt alloys; Magnetic storage; Magnetooptical devices; Microscopes; Multilayers; Magnetic force microscopes; Magnetic measuring instruments.
Abstract: ...
A set of reference samples for comparing the results obtained with different magnetic force microscopes (MFM) has been prepared. These samples consist of CoNi/Pt magneto-optic multilayers with different thicknesses. The magnetic properties of the multilayer are tailored in such a way that a very fine stripe domain structure occurs in remanence. On top of this intrinsic domain structure, bits were written thermomagnetically using different laser powers. These samples have been imaged in six different laboratories employing both home-built and commercial magnetic force microscopes. The resolution obtained with these different microscopes, tips and measurement methods varies between 30 and 100 nm. © 1998 Elsevier Science B.V. All rights reserved.
document
Porthun, Steffen; Abelmann, Leon; Lodder, Cock;
Journal of Magnetism and Magnetic Materials,
Volume 182, Issue 1-2, pp. 238 – 273, 1998. DOI: 10.1016/S0304-8853(97)01010-X
Keywords: ...
Magnetic domains; Magnetic field effects; Magnetic heads; Magnetic recording; Magnetooptical devices; Microscopic examination; Magnetic force microscopy; Magnetic imaging; Magnetic structures; Soft magnetic materials; Magnetic thin films.
Abstract: ...
This paper discusses various aspect of magnetic force microscopy (MFM) for use in the field of high density magnetic recording. After an introduction of the most important magnetic imaging techniques, an overview is given of the operation and theory of MFM. The developments in instrumentation, MFM tips, quantification of MFM data, high resolution imaging and application of external fields is discussed. Examples are given of the applications of MFM, such as the characterization of heads, magnetic structures (bits) in longitudinal and perpendicular recording media, bits in magneto-optic films and domain structures in soft magnetic materials. © 1998 Elsevier Science B.V. All rights reserved.
document
Haast, M. A. M.; Schuurhuis, J. R.; Abelmann, L.; Lodder, J. C.; Popma, T. J.;
IEEE Transactions on Magnetics,
Volume 34, Issue 4 PART 1, pp. 1006 – 1008, 1998. All Open Access, Green Open Access. DOI: 10.1109/20.706339
Keywords: ...
Cobalt alloys; Coercive force; Lithography; Magnetic hysteresis; Magnetic recording; Metallic superlattices; Platinum; Laser interference lithography; Magnetic force microscopy; Magnetic films.
Abstract: ...
With laser interference lithography CosoNiso/Pt multilayers with perpendicular magnetic anisotropy have been patterned into regular matrices of submicron sized dots. Their magnetic properties have been studied with Vibrating Sample Magnetojnetry. Compared to continuous multilayers (Hc =15 kA/m) the coercivity for the patterned multilayers is much larger (H, = 115-270 kA/m). Though the hysteresis curves of ISO nm dots and 60 nm dots have identical shapes, virgin curves seem to indicate that the 180 urn dots are multidomain while the 60 nm dots are single domain. The latter has been confirmed with Magnetic Force Microscopy observations. © 1998 IEEE.
document
Abelmann, Leon; Lodder, Cock;
Thin Solid Films,
Volume 305, Issue 1-2, pp. 1 – 21, 1997. DOI: 10.1016/S0040-6090(97)00095-3
Keywords: ...
Diffusion in solids; Evaporation; Film growth; Mathematical models; Surface phenomena; Surface structure; Thermal effects; Oblique evaporation; Thin films.
Abstract: ...
The special structure of obliquely evaporated films has its origin in shadowing phenomena during film growth. Because of shadowing, the film consists of bundles of inclined columns with the bundles being aligned perpendicularly to the vapour incidence direction. The column inclination angle lies between the film normal and the vapour incidence direction. Different models found in literature relating process parameters and film structure are discussed. It is found that surface diffusion plays an important role, especially with regard to the difference between random and directional surface diffusion. The latter is induced by the oblique evaporation process. A quantitative expression is given for the relation between process conditions and surface diffusion including the influence of substrate temperature, rate and contamination with residual gasses. Using these models and adding our new calculations, the relation between surface diffusion and film structure is discussed in detail and found to be consistent with measurements published in the literature. © 1997 Elsevier Science S.A.
document
Immink, A. H. J.; Bijker, M. D.; Abelmann, L.; Lodder, J. C.;
Journal of Magnetism and Magnetic Materials,
Volume 155, Issue 1-3, pp. 279 – 283, 1996. All Open Access, Green Open Access. DOI: 10.1016/0304-8853(95)00730-X
Keywords: ...
Composition; Deposition; Etching; Magnetic recording; Magnetization; Magnetostatics; Morphology; Oxidation; Oxygen; Pressure effects; Scanning electron microscopy; Substrates; Double layered tapes; Metal evaporated tape; Mini-rollcoater set up; Negative magnetostatic interaction; Oxygen concentration; Magnetic tape.
Abstract: ...
A series of experimental double layered ME tapes with different oxygen concentrations were produced using an experimental mini-rollcoater set-up. δM measurements on these tapes indicate a negative (magnetostatic) interaction between the individual layers.
document
Abelmann, Leon; Kambersky, Vladimir; Lodder, Cock; Popma, Theo J. A.;
IEEE Transactions on Magnetics,
Volume 29, Issue 6 pt 1, pp. 3022 – 3024, 1993. All Open Access, Green Open Access. DOI: 10.1109/20.281089
Keywords: ...
Anisotropy; Cobalt compounds; Crystal orientation; Crystal structure; Fourier transforms; Harmonic generation; Magnetic films; Magnetization; Matrix algebra; Textures; Fourier analysis; Magnetic anisotropy energy; Oblique anisotropy; Spherical harmonics; Torque measurement.
Abstract: ...
A measurement method is discussed to determine the magnetic anisotropy energy in a sample without assuming an a priori model for the origins of the anisotropy. The measurement procedure involves torque measurements in five different planes. Since it is especially useful for films with an oblique anisotropy axis, the method is illustrated on an obliquely evaporated Co80Ni20 film.
document
Aitlamine, H.; Abelmann, L.; Puchalska, I. B.;
Journal of Applied Physics,
Volume 71, Issue 1, pp. 353 – 361, 1992. All Open Access, Bronze Open Access, Green Open Access. DOI: 10.1063/1.350715
Abstract: ...
Oblique and in-plane anisotropies in obliquely evaporated NiCo thin films were investigated in order to understand their origin. All the compositions studied clearly show the effect of columnar grain morphology coupled with some intrinsic factors such as magnetostriction and crystallinity. Energy calculations are undertaken to explain the effect of these anisotropies on domain structures and the existence of strong and weak stripe domains depending on the composition and incidence angle.
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