Ultrasonically powered piezoelectric generators for bio-implantable sensors: Plate versus diaphragm

This article is a comparative study of the design spaces of two bio-implantable acoustically excited generator architectures: the bulk-mode piezoelectric plate (plate) and the flexure-mode unimorph piezoelectric diaphragm (diaphragm). The acoustic to electrical power transducers, or generators, are part of an acoustic, or ultrasonic, power transfer system for implantable sensors and medical devices such as glucose monitors, metabolic monitors, and drug delivery systems. Scalable network equivalent models are presented and used to predict that for sub-millimeter size devices, the diaphragm architecture generates more power than the plate architecture and is less sensitive to absorption power losses with increased implant depth. The models are compared to the experimental data from centimeter-size devices. This article will present and compare the power loss mechanisms and total power generated for each of the architectures as a function of diameter, aspect ratio, and implanted depth.