Tiago Costa

1. Analysis of Power Losses and the Efficacy of Power Minimization Strategies in Multichannel Electrical Stimulation Systems
   Francesc Varkevisser; Wouter A. Serdijn; Tiago L. Costa;
   J. Neural Eng.,
   Februrary 2026. DOI: 10.1088/1741-2552/ae409c
   
   Abstract: ...

   Objective. Neuroprosthetic devices require multichannel stimulator systems with an increasing number of channels. However, there are inherent power losses in typical multichannel stimulation circuits caused by mismatches between the power supply voltage and the voltage required at each electrode to successfully stimulate tissue. This imposes a bottleneck towards high-channel-count devices, which is particularly severe in wirelessly-powered devices. Hence, advances in the power efficiency of stimulation systems are critical. To support these advances, this paper presents a methodology to identify and quantify power losses associated with different power supply scaling strategies in multichannel stimulation systems. Approach. The methodology uses distributions of stimulation amplitudes and electrode impedances to calculate power losses in multichannel systems. Experimental data from prior studies spanning various stimulation applications were analyzed to evaluate the performance of fixed, global, and stepped supply scaling methods, focusing on their impact on power dissipation and efficiency. Main Results. Variability in output conditions results in low power efficiency in multichannel stimulation systems across all applications. Stepped voltage scaling demonstrates substantial efficiency improvements, achieving an increase of 43 % to 100 %, particularly in high-channel-count applications with significant variability in tissue impedance. In contrast, global scaling proved effective only in systems with fewer channels and minimal inter-channel variation. Significance. The findings highlight the importance of tailoring power management strategies to specific applications to optimize efficiency while minimizing system complexity. The proposed methodology provides a framework for evaluating trade-offs between efficiency and system complexity, facilitating the design of more scalable and power-efficient neurostimulation systems.
   
   document

2. Piezoelectric ion gated organic electrochemical transistors for efficient vibration sensing and on-site amplification
   Linta Sohail; Sofia Drakopoulou; Tiago L. Costa; George D. Spyropoulos;
   npj flexible electronics,
   Volume 9, Issue 39, May 2025. DOI: https://doi.org/10.1038/s41528-025-00418-3
   document

3. Autonomous Output Supply Scaling for Efficient Multichannel Electrical Stimulation
   Francesc Varkevisser; Linta Sohail; Sofia Drakopoulou; George D. Spyropoulos; Tiago L. Costa; Wouter A. Serdijn;
   IEEE Transactions on Circuits and Systems I: Regular Papers,
   2025. DOI: 10.1109/TCSI.2025.3621587
   document

4. A Single-Inductor-Based High-Voltage Transmit Beamformer for Wearable Ultrasound Devices Achieving 88% fCV2 Power Reduction
   Peng Guo; Zu-Yao Chang; Michiel A.P. Pertijs; Tiago L. Costa;
   In 2025 IEEE International Solid-State Circuits Conference (ISSCC),
   2025. DOI: 10.1109/ISSCC49661.2025.10904513

5. A Programmable-Gain Floating Inverter Low-Noise Amplifier for Ultrasound Imaging Analog Frontends
   Diogo Dias; Tiago L. Costa; João Goes;
   In 2025 IEEE International Symposium on Circuits and Systems (ISCAS),
   2025. DOI: 10.1109/ISCAS56072.2025.11043193

6. PMUT and CMUT Devices for Biomedical Applications: A Review
   Elisabetta Moisello; Lara Novaresi; Eshani Sarkar; Piero Malcovati; Tiago L. Costa; Edoardo Bonizzoni;
   IEEE Access,
   2024. DOI: 10.1109/ACCESS.2024.3359906

7. Feasibility Study for a High-Frequency Flexible Ultrasonic Cuff for High-Precision Vagus Nerve Ultrasound Neuromodulation
   Cornelis van Damme; Gandhika K. Wardhana; Andrada Iulia Velea; Vasiliki Giagka; Tiago L. Costa;
   IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
   Volume 71, Issue 7, 2024. DOI: 10.1109/TUFFC.2024.3381923
   document

8. Anti-reflective Microengineered Substrate for in vitro Ultrasound Neuromodulation
   Gandhika Wardhana; Tiago L. Costa; Massimo Mastrangeli;
   In 2024 IEEE Ultrasonics, Ferroelectrics, and Frequency Control Joint Symposium (UFFC-JS),
   2024. DOI: 10.1109/UFFC-JS60046.2024.10793577

9. A PVT-Robust Open-loop Gm-Ratio ×16 Gain Residue Amplifier for >1 GS/s Pipelined ADCs
   Diogo Dias; João Goes; Tiago L. Costa;
   In 2024 IEEE International Symposium on Circuits and Systems (ISCAS),
   2024. DOI: 10.1109/ISCAS58744.2024.10558154

10. 2D Phased Array Driving Scheme Optimization for Ultrasound Neuromodulation
    Masoumeh Aqamolaei; Tiago L. Costa;
    In 2024 IEEE Ultrasonics, Ferroelectrics, and Frequency Control Joint Symposium (UFFC-JS),
    2024. DOI: 10.1109/UFFC-JS60046.2024.10793494

11. Ultrasound phased array patch on flexible CMOS and methods for fabricating thereof
    Kenneth Shepard; Tiago Costa; Kevin Tien; Chen Shi;
    Patent, US11937981B2, 2024.
    document

12. A 2D Ultrasound Phased-Array Transmitter ASIC for High-Frequency US Stimulation and Powering
    Hassan Rivandi; Tiago L. Costa;
    IEEE Transactions on Biomedical Circuits and Systems (IEEE TbioCAS),
    2023. DOI: 10.1109/TBCAS.2023.3288891

13. Hybrid neuroelectronics: towards a solution-centric way of thinking about complex problems in neurostimulation tools
    Sofia Drakopoulou; Francesc Varkevisser; Linta Sohail; Masoumeh Aqamolaei; Tiago L. Costa; George D. Spyropoulos;
    Frontiers in Electronics,
    2023. DOI: https://doi.org/10.3389/felec.2023.1250655

14. Low-cost shaping of electrical stimulation waveforms for bioelectronic medicine with improved efficiency and selectivity
    Amin Rashidi; Francesc Varkevisser; Vasiliki Giagka; Tiago L. Costa; Wouter A. Serdijn;
    In in Proc. 9th Dutch Biomedical Engineering Conf. (BME) 2023,
    January 2023.
    document

15. Multichannel Current-Mode Stimulator with Channel-Specific Regulated Power Supply
    Francesc Varkevisser; Tiago L. Costa; Wouter A. Serdijn;
    In Proc. 2023 IEEE Biomedical Circuits and Systems Conference (BioCAS),
    Toronto, IEEE, 19-21 October 2023.
    document

16. An Energy-Efficient High-Voltage Pulser for High-Frequency Ultrasound Medical Applications
    Yidi Xiao; Hassan Rivandi; Tiago L. Costa;
    In IEEE International Symposium on Biomedical Circuits and Systems (IEEE BioCAS),
    2023.

17. Energy efficiency of pulse shaping in electrical stimulation: the interdependence of biophysical effects and circuit design losses
    Francesc Varkevisser; Tiago Costa; Wouter Serdijn;
    Biomedical Physics & Engineering Express,
    Volume 8, Issue 6, 13 September 2022. DOI: 10.1088/2057-1976/ac8c47
    document

18. Electronic Platforms and Signal Processing for Magnetoresistive-Based Biochips
    José Germano; Tiago L. Costa; Filipe A. Cardoso; José Amaral; Susana Cardoso; Paulo P. Freitas; Moisés S. Piedade;
    Springer, , 2022. DOI: https://doi.org/10.1007/978-1-4614-3447-4_20

19. Stent with Piezoelectric Transducers for High Spatial Resolution Ultrasound Neuromodulation - a Finite Element Analysis
    I. Dilevicius; W. A. Serdijn; T. L. Costa;
    In proc. 2022 44th Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC),
    Glasgow, UK, IEEE, pp. 4966-4969, July 2022. DOI: 10.1109/EMBC48229.2022.9871956
    document

20. Pre-Filtering of Stimuli for Improved Energy Efficiency in Electrical Neural Stimulation
    Francesc Varkevisser; Amin Rashidi; Tiago L. Costa; Vasiliki Giagka; Wouter A. Serdijn;
    In Proc. IEEE Biomedical Circuits and Systems Conference (BioCAS) 2022,
    IEEE, October 2022.
    document

21. Design of a Flexible Transducer Array and Characterisation of Piezoelectric Sensors for Curvature Compensation
    Christiaan Boerkamp; Tiago L. Costa; Jovana Jovanova;
    In Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS),
    2022. DOI: https://doi.org/10.1115/SMASIS2022-90707

22. A Parasitic Resistance Extraction Tool Leveraged by Image Processing
    Diogo Dias; João Goes; Tiago L. Costa;
    In IEEE International Symposium on Circuits and Systems (IEEE ISCAS),
    2022. DOI: 10.1109/ISCAS48785.2022.9937879

23. Maximization of Transmitted Acoustic Intensity from Silicon Integrated Piezoelectric Ultrasound Transducers
    Gandhika W. Wardhana; Massimo Mastrangeli; Tiago L. Costa;
    In IEEE International Ultrasonics Symposium (IEEE IUS),
    2022. DOI: 10.1109/IUS54386.2022.9957646

24. A High-Frequency Beamforming Channel for Ultrasound Stimulation and Ultrasonic Powering
    Hassan Rivandi; Ishaan Ghosh; Tiago L. Costa;
    In IEEE International Symposium on Biomedical Circuits and Systems (IEEE BioCAS),
    2022. DOI: 10.1109/BioCAS54905.2022.9948550

25. Application of a sub–0.1-mm3 implantable mote for in vivo real-time wireless temperature sensing
    Chen Shi; Victoria Andino-Pavlovsky; Stephen A. Lee; Tiago Costa; Jeffrey Elloian; Elisa E. Konofagou; Kenneth L. Shepard;
    Science Advances,
    Volume 7, Issue 19, pp. eabf6312, 2021. DOI: 10.1126/sciadv.abf6312
    document

26. An Integrated 2D Ultrasound Phased Array Transmitter in CMOS with Pixel Pitch-Matched Beamforming
    Tiago Costa; Chen Shi; Kevin Tien; Jeffrey Elloian; Filipe A. Cardoso; Kenneth Shepard;
    IEEE Transactions on Biomedical Circuits and Systems,
    pp. 1, July 2021. DOI: 10.1109/TBCAS.2021.3096722
    document

27. Bidirectional Bioelectronic Interfaces: System Design and Circuit Implications
    Y. Liu; A. Urso; Martins da Ponte, Ronaldo; T. Costa; V. Valente; V. Giagka; W.A. Serdijn; T.G. Constandinou; T. Denison;
    IEEE Solid-State Circuits Magazine,
    Volume 12, Issue 2, pp. 30-46, 23 June 2020. DOI: 10.1109/MSSC.2020.2987506
    document

28. A 0.065-mm(3) Monolithically-Integrated Ultrasonic Wireless Sensing Mote for Real-Time Physiological Temperature MonitoringSyst
    C. Shi; T. Costa; J. Elloian; Y. Zhang; K.L. Shepard;
    IEEE Trans Biomed Circuits,
    Volume 14, Issue 3, pp. 412-424, June 2020. DOI: 10.1109/TBCAS.2020.2971066.
    document

29. Ablation of piezoelectric polyvinylidene fluoride with a 193 nm excimer laser
    J. Elloian; J. Sherman; T. Costa; C. Shi; K. Shepard;
    Journal of Vacuum Science & Technology A,
    Volume 38, Issue 3, pp. 033202, February 2020. DOI: 10.1116/1.5142494
    document

30. A CMOS 2D Transmit Beamformer with Integrated PZT Ultrasound Transducers for Neuromodulation
    T. Costa; C. Shi; K. Tien; K.L. Shepard;
    In Proc. 2019 IEEE Custom Integrated Circuits Conference (CICC'2019),
    Austin, TX, USA, IEEE, pp. 1-4, 21-24 April 2019. DOI: 10.1109/CICC.2019.8780236
    document

31. Monolithic Integration of Micron-scale Piezoelectric Materials with CMOS for Biomedical Applications
    C. Shi; T. Costa; J. Elloian; K.L. Shepard;
    In Proc. 2018 IEEE International Electron Devices Meeting (IEDM'2018),
    San Francisco, CA, USA, IEEE, pp. 4.5.1-4.5.4, Dec. 1-5 2018. DOI: 10.1109/IEDM.2018.8614632
    document

32. A CMOS Front-End with Integrated Magnetoresistive Sensors for Biomolecular Recognition Detection Applications
    Costa, T.; Cardoso, F.A.; Germano, J.; Freitas, P.P.; Piedade, M.S.;
    IEEE Transactions on Biomedical Circuits and Systems,
    Volume 11, Issue 5, pp. 988-1000, 2017. DOI: 10.1109/TBCAS.2017.2743685

33. Monolithic device combining CMOS with magnetoresistive sensors
    Filipe A. Cardoso; Tiago L. Costa; José Germano; Moisés S. Piedade;
    Patent, US9567626B2, 2017.

34. Semi-quantitative method for streptococci magnetic detection in raw milk
    Duarte, C.; Costa, T.; Carneiro, C.; Soares, R.; Jitariu, A.; Cardoso, S.; Piedade, M.; Bexiga, R.; Freitas, P.;
    Biosensors,
    Volume 6, Issue 2, 2016. DOI: 10.3390/bios6020019

35. Design and optimization of a CMOS front-end for magnetoresistive sensor based biomolecular recognition detection
    Costa, T.; Germano, J.; Piedade, M.S.; Cardoso, F.A.; Freitas, P.P.;
    In Proceedings - IEEE International Symposium on Circuits and Systems,
    pp. 2859-2862, 2016. DOI: 10.1109/ISCAS.2016.7539189

36. MagCMOS
    Costa, T.; Cardoso, F.A.; Piedade, M.S.; Freitas, P.P.;
    In Handbook of Bioelectronics: Directly Interfacing Electronics and Biological Systems,
    Cambridge University Press, 2015. DOI: 10.1017/CBO9781139629539.015

37. Live demonstration: A CMOS ASIC for precise reading of a Magnetoresistive sensor array for NDT
    Caetano, D.M.; Piedade, M.; Graca, J.; Fernandes, J.; Rosado, L.; Costa, T.;
    In Proceedings - IEEE International Symposium on Circuits and Systems,
    pp. 1906, 2015. DOI: 10.1109/ISCAS.2015.7169039

38. A neuronal signal detector for biologically generated magnetic fields
    Costa, T.; Piedade, M.S.; Germano, J.; Amaral, J.; Freitas, P.P.;
    IEEE Transactions on Instrumentation and Measurement,
    Volume 63, Issue 5, pp. 1171-1180, 2014. DOI: 10.1109/TIM.2013.2296417

39. Integration of TMR sensors in silicon microneedles for magnetic measurements of neurons
    Amaral, J.; Pinto, V.; Costa, T.; Gaspar, J.; Ferreira, R.; Paz, E.; Cardoso, S.; Freitas, P.P.;
    IEEE Transactions on Magnetics,
    Volume 49, Issue 7, pp. 3512-3515, 2013. DOI: 10.1109/TMAG.2013.2239274

40. Measuring brain activity with magnetoresistive sensors integrated in micromachined probe needles
    Amaral, J.; Gaspar, J.; Pinto, V.; Costa, T.; Sousa, N.; Cardoso, S.; Freitas, P.;
    Applied Physics A: Materials Science and Processing,
    Volume 111, Issue 2, pp. 407-412, 2013. DOI: 10.1007/s00339-013-7621-7

41. CMOS instrumentation system for matrix-based magnetoresistive biosensors
    Costa, T.; Piedade, M.S.; Cardoso, F.A.; Freitas, P.P.;
    In Conference Record - IEEE Instrumentation and Measurement Technology Conference,
    pp. 1315-1318, 2013. DOI: 10.1109/I2MTC.2013.6555626

42. An instrumentation system based on magnetoresistive sensors for neuronal signal detection
    Costa, T.; Piedade, M.S.; Germano, J.; Amaral, J.; Freitas, P.P.;
    In Conference Record - IEEE Instrumentation and Measurement Technology Conference,
    pp. 1074-1077, 2013. DOI: 10.1109/I2MTC.2013.6555579

43. Integration of magnetoresistive biochips on a CMOS circuit
    Cardoso, F.A.; Costa, T.; Germano, J.; Cardoso, S.; Borme, J.; Gaspar, J.; Fernandes, J.R.; Piedade, M.S.; Freitas, P.P.;
    IEEE Transactions on Magnetics,
    Volume 48, Issue 11, pp. 3784-3787, 2012. DOI: 10.1109/TMAG.2012.2198449

44. An ultra-low noise current source for magnetoresistive biosensors biasing
    Costa, T.; Piedade, M.S.; Santos, M.;
    In 2012 IEEE Biomedical Circuits and Systems Conference: Intelligent Biomedical Electronics and Systems for Better Life and Better Environment, BioCAS 2012 - Conference Publications,
    pp. 73-76, 2012. DOI: 10.1109/BioCAS.2012.6418507

45. A CMOS circuit for precise reading of matrix addressed magnetoresistive biosensors
    Costa, T.; Piedade, M.S.; Fernandes, J.R.;
    In 2011 IEEE Biomedical Circuits and Systems Conference, BioCAS 2011,
    pp. 389-392, 2011. DOI: 10.1109/BioCAS.2011.6107809

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