Acoustic micro-resonator utilizing hemispherical air cavity for sensitivity enhancement

We report the modelling, feasibility study, parametric design, fabrication approach, and measurements of a mechanical transducer with sensitivity amplified by an air cavity exhibiting the Helmholtz resonance effect. The device features a cantilever with sputtered zinc oxide for piezoelectric sensing coupled to a microfabricated hemispherical chamber. A model was developed and assessed using FEM simulations, and the resulting model was applied to generate a set of device parameters to provide up to 41 dB in sensitivity enhancement. Two devices were fabricated and tested, and showed improvements in sensitivity by factors of 11.14 and 13.9, experimentally demonstrating the feasibility of this approach.