Energy Harvesting for a Microscale Biosensing Device
via Piezoelectric Micromachined Ultrasonic Transducers

Microdevices with dimensions comparable to a blood cell, i.e., tens of micrometers, show
great potential for use in the human body. They can be adopted to identify the source
of diseases, track their evolution and enhance the effectiveness of therapies, significantly
improving patients’ quality of life. A key challenge is how to power the devices, which
should ideally be obtained wireless from a remote source. Piezoelectric micromachined
ultrasonic transducers (pMUTs) offer a solution thanks to their ability to generate and
collect energy via acoustic waves. In this work, numerical simulations of transmitter pMUT
arrays are performed with the aim of generating an acoustic wave synchronized with a
single pMUT or pMUT array receiver. The latter is intended for insertion in the human body.
The characteristics required to switch on and power nano-electronics, in terms of generated
voltage and electrical power at the receiver, are studied in ballistic gel, a material that mimics
human organs. Focus is on a bio-compatible material for the piezoelectric layer, aluminum
nitride enriched with scandium. Coupled electromechanical and acoustic simulations
show that, of the considered pMUT devices, an 8 X 8 transmitter array combined with a
single-device receiver (with a 50 μm pitch) or a 2 X 2 receiver array provide alternative
options, with each offering advantages in terms of voltage amplitude or power at steady
state. The overall dimension of the receiver, at maximum only 100 X 100 μm2, is compatible
with a future proof-of-concept biosensing platform test chip.