Piezoelectric energy harvesting for bio MEMS applications

A simple design study is conducted to investigate the feasibility of using piezoelectric materials in a power supply for an in vivo MEMS application. An analysis is presented comparing the 33- and 31- modes of operation for a piezoelectric generator. It will be shown that a transversely loaded membrane (31-mode) or thin plate element has a mechanical advantage in converting applied pressure to working stress for piezoelectric conversion. A design study is carried out using a square PZT-5A membrane driven by a fluctuating pressure source (blood pressure). The expected power output from a 1 cm(2) plate is calculated for a range of thicknesses, along with the power output from a 9 mum thick plate for a range of areas. Additionally, the feasibility, of providing intermittent power instead of continuous power or increased excitation frequency will be shown. The primary conclusion of this analysis is that an in vivo piezoelectric generator on a size scale of 1 cm(2) may be able to power a A EAE application in the muW power range continuously, and up to the m W range intermittently.