[2025] Reconfigurable Acoustic Systems via Electrowetting-on-Dielectric (EWOD) on PZT transducer

Reconfigurable acoustic systems are critical for emerging biomedical applications
such as high-resolution imaging, targeted drug delivery, neuromodulation, and
tissue ablation. Current solutions often rely on complex phased array transducers
or mechanically tunable metamaterials, both of which can be expensive and
difficult to miniaturize. This project proposes an approach that uses electrowetting
on dielectric (EWOD) to manipulate liquid droplets or fluidic layers placed on a
piezoelectric (PZT) transducer, thereby dynamically tuning acoustic wave
propagation characteristics (e.g., focus, phase, amplitude). This method enables
low-power, rapid reconfiguration and has been extensively used in lab-on-a-chip
devices. This approach takes advantage of established microfluidic techniques for
PZT transducers [1].
When a droplet is placed on the transducer surface, it can act as an acoustic lens,
altering local boundary conditions and changing how sound waves propagate. By
varying the position, volume, or shape of the droplet, it is possible to control
droplet-air or droplet-fluid interface, thereby controlling how acoustic waves are
refracted, focused, or defocused. Furthermore, by positioning multiple droplets or
by moving a droplet across various electrode “pixels,” phase shifts could be
introduced at different regions of the transducer surface. This creates a dynamic
phase profile that can steer or shape the emitted beam, much like the phased
array—but potentially with fewer active transducer elements. By employing
electrowetting on dielectric (EWOD) technology on a PZT transducer, this project
demonstrates a new path to tunable, reconfigurable acoustic systems in real time
—without the complexity and cost of large phased arrays. Through droplet
manipulation, one can actively shape and steer ultrasonic waves for critical
biomedical applications such as neuromodulation, targeted drug delivery, and
adaptive imaging. This approach could yield more compact, efficient, and versatile
ultrasonic devices, potentially transforming how clinicians and researchers
harness ultrasound in next-generation medical procedures.

References:

[1] Z. H. Hsieh, C. H. Fan, Y. C. Lin, and C. K. Yeh, “Electrowetting-driven liquid
lens for ultrasound: Enabling controllable focal length and flexible beam
steering,” Ultrasonics, vol. 135, Dec. 2023, doi: 10.1016/j.ultras.2023.107147.

Assignment

1. Literature review on EWOD and COMSOL modelling to optimize droplet
shape and positions to predict changes in acoustic wave propagation.
2. Development of EWOD-on-PZT set-up using micro-fabrication techniques
and system integration. Acoustic Validation of the prototype using
hydrophone in a DI water-tank.

Requirements

MSc students from Microelectronics, Biomedical Engineering, Mechanical
Engineering or Applied Physics. Prior knowledge on COMSOL is preferred.
Interested students should include their CV, the list of courses attended, and a
motivation letter, and send it to Tiago Costa (t.m.l.dacosta@tudelft.nl) and Eshani
Sarkar (E.Sarkar@tudelft.nl).

Contact

Last modified: 2025-02-28