Threshold Pressure Sensing Using Parametric Resonance in Electrostatic MEMS

This study illustrates the concept of threshold pressure sensing using the parametric resonance of an electrostatic levitation mechanism. The electrostatic levitation allows the oscillations in the opposite direction of the substrate, thereby not limited to small gaps. The pressure sensor detects the pressure drop below a threshold value by triggering the parametric resonance with significant peak to peak dynamic amplitude changes (~ 25 μm). This detection relies on the fact that the instability region expands when the pressure drop forces the amplitude jump up to the higher oscillation branch. This significant change in the resonator amplitude can be related to a large capacitance variation indicating the threshold pressure. A mathematical model of the resonator is presented to show the working principle of the sensor through frequency response. Our experimental results show that the threshold pressure the sensor detects, can be adjusted by the AC voltage it receives.