Piezoelectric Micro-Machined Ultrasonic Transducer (Pmut) For Energy Harvesting

Micro-electromechanical devices dedicated to energy scavenging purpose have yield an increasing interest for a few years [1]. In this paper we report on the fabrication of PZT/Si piezoelectric micro-machined ultrasonic transducers (pMUT) first designed to ultrasonic imaging applications that may be used as a mechanical to electrical energy transformer for energy harvesting This work aims to demonstrate the ability of pMUT to convert inertial energy into electrical energy through the piezoelectric layer deposited atop silicon membrane. The diameter of the membrane ranges from 132 pm to 600 pm and the thickness of silicon and PZT are respectively set to 1 and 2 pm. It is shown that the membrane exhibit a deformed shape, as the PZT is under lateral compression, with a maximum deflection equal to more than 1.5 times the equivalent membrane thickness. We first aimed to design a bistable micro power generator as the device could take two stable states that respectively corresponds to the case of PZT is under lateral compression and the case of PZT is under lateral extension (the symmetric deformation state). First experiments consist in testing the capability of the pMUT to change from one state to the other by a simple and weak mechanical excitation ranging from 0.5g to 2g acceleration.