Bio-implantable medical devices need a reliable and stable source of power to perform effectively. Although batteries can be the first candidate to power implantable devices as they provide high energy density, they cannot supply power for long periods of time and therefore, they must be periodically replaced or recharged. Battery replacement is particularly difficult as it requires surgery. In this paper, we develop a micromachined ultrasonic power generating receiver with a size of 3.5mmx3.5mm capable of providing sufficient power for implantable medical devices. The ultrasound receiver takes the form of a unimorph diaphragm consisting of PZT on silicon. We dice bulk PZT with a thickness of 127 μm and bond the diced pieces to a silicon wafer. In order to get a 50 μm thick PZT layer, which is needed for optimal power transfer, we mechanically lap and polish the bonded PZT. We numerically investigate the performance of the fabricated receiver with inner and outer electrodes on the surface of the PZT. Using COMSOL simulations, we analyze the effect of different sizes of inner and outer electrodes under the actuation of the inner electrode in order to find the optimum electrode sizes. We show that when the transmitter is generating an input power less than Food and Drug Administration limits, the receiver can provide sufficient voltage and power for many implantable devices. Furthermore, the process developed can be used to fabricate significantly smaller devices than the one characterized, which enables further miniaturization of bio-implanted systems.

Date Published: 11 April 2017
PDF: 7 pages
Proc. SPIE 10164, Active and Passive Smart Structures and Integrated Systems 2017, 1016416 (11 April 2017); doi: 10.1117/12.2260059

Published in SPIE Proceedings Vol. 10164:
Active and Passive Smart Structures and Integrated Systems 2017
Gyuhae Park, Editor(s)