A MEMS-Scale Ultrasonic Power Receiver for Biomedical Implants

摘要

Bio-implantable medical devices need a reliable and stable source of power to perform effectively. Although batteries are typically the first candidate to power implantable devices, they have a limited lifetime and must be periodically replaced or recharged. To alleviate this issue, ultrasonic power transfer systems can wirelessly power bio-implantable devices. Diaphragm structures which use piezoelectric materials (also known as piezoelectric micromachined ultrasonic transducers) can be fabricated on a small scale suitable for implantable devices. Diaphragms can be fabricated by deposition of lead zirconate titanate (PZT) films on a non-piezoelectric material. However, current deposition techniques cannot provide PZT thicknesses more than about 6 μm. We numerically investigate the performance of a square ultrasonic PZT receiver with inner and outer electrodes. Using COMSOL simulations, we optimize the piezoelectric film thickness for a 2 mm × 2 mm diaphragm with a silicon substrate of 50 μm and find the optimal thickness to be 20 μm for a maximum output power delivered to an optimal load. We fabricate a micromachined ultrasonic power-generating receiver capable of providing sufficient power for implantable medical devices using bulk PZT. We show that when a transmitter is generating an input power intensity of 322 mW/cm