Design and Simulation of Piezoelectric Wideband Acoustic Sensor Covered with Organic Film

A wideband acoustic sensor is reported in which the cantilevers are covered with an organic film in a piezoelectric micro-electro mechanical systems (MEMS) acoustic transducer. Coating the gap between the cantilevers with an organic film expands the low-frequency sensitivity, and connecting the cantilevers with an organic film increases the resonance frequency. Therefore, a broadband acoustic sensor can be realized [1]. However, coating with an organic film lowers the sensitivity, making the selection of the material for the organic film crucial. In this study, we perform finite element method (FEM) simulations using a combination of piezoelectric materials and organic films and provide guidelines for selecting organic films. Simulations are performed using AlN, ZnO, and polyvinylidene fluoride (PVDF) as piezoelectric materials. The results show that the larger the Young's modulus ratio between the piezoelectric layer and the organic film, the lesser the effect of the organic film, which is expected to suppress the decrease in sensitivity caused by the organic film. The simulation results of the effective stress distribution from the fixed end to the free end of the cantilever confirms that there exists a region where the effective stress is high near the tip of the cantilever. This suggests that sensitivity can be improved by placing the electrode near the tip of the cantilever.