Effect of seismic mass thickness on the resonance frequency of cantilever type piezoelectric energy harvester

Abstract

Piezoelectric energy harvesters find applicability in remote area of application because of simple design and operation. Micro-electromechanical system (MEMS) process technology is utilized to fabricate these cantilever based structures. Piezoelectric layer length and thickness are the key parameters for controlling the resonance frequency. However, for further lowering the resonance frequency and having optimal output a seismic mass is introduced at the tip of the cantilever structure. In this paper, the effect of increasing the thickness of the seismic mass on the resonance frequency of the cantilever structure has been investigated. Finite Element Method (FEM) results have been obtained using Coventorware software by varying the thickness of the seismic mass 10–20 µm. It has been observed the variation of the thickness of the seismic mass has an effect on the resonance frequency of the cantilever. As the thickness increases, the volume of the seismic mass increases and the resonance frequency of the cantilever decreases. The base of the cantilever is Silicon; Aluminum Nitride (AlN) piezoelectric material has been selected of 3 µm thickness. The length of the silicon cantilever is varied from 1600 to 2500 µm and the resonance frequency is obtained. At a length of 1600 µm, variation of seismic mass thickness from 10 to 15 µm results in reduction in resonance frequency by 17.27% whereas when seismic mass is varied from 15 to 20 µm the resonance frequency is reduced by 12.63%.