A Piezoresistive Vibration Sensor with Liquid on Corrugated Membrane

This paper reports on a MEMS vibration sensor with a structure of liquid on a thin Parylene membrane which has a piezoresistive beam attached underneath. The proposed sensor has a high sensitivity over a wide range of frequency (from several Hz to several hundred kHz) by utilizing the inertia force of the liquid at low frequency and surface tension wave at high frequency. Most significantly, this sensor design can prevent liquid leakage which is a crucial problem in the conventional sensor which has a piezoresistive beam placed directly underneath liquid. Furthermore, sensitivity improvement using corrugated Parylene membranes was experimentally confirmed.