MEMS based piezoelectric ultrasonic energy harvester for self-powered under-water applications

Acoustic energy transfer (AET) has been widely used in self-powered under-water or implantable biomedical systems. But most of the receivers in AET for energy harvesting are bulk lead zirconate titanante (PZT) transducers. The large volume and limited bandwidth greatly hinder the integration and energy harvesting capability of the bulk receivers. Therefore, in this paper we propose a new microelectromechanical system (MEMS) based piezoelectric ultrasonic energy harvester (PUEH) with miniaturized size and large bandwidth to replace the receiver in AET. The PUEH is ideally suitable for integration with self-powered system since it is fabricated from miniaturized PZT diaphragm array. Due to the large length/width aspect ratio design of the thin PZT diaphragm, several resonant modes can be excited within a narrow frequency range. When the PUEH operates in water medium, excited resonant modes tend to merge together, leading to a broadband behavior of the PUEH. The proposed PUEH has a -6 dB bandwidth of 74.5% with a central frequency of 350 kHz. The PUEH has the ability to harvest energy from a large frequency range from 220 kHz to 930 kHz.