Effects of pressure on suspended micromechanical membrane arrays

TL;DR

This study investigates how air pressure influences the mechanical resonance and damping of suspended silicon nitride membrane arrays, revealing pressure-dependent frequency shifts, damping behaviors, and mode hybridization effects.

Contribution

It provides a detailed analysis of pressure effects on micromechanical membranes, including a model explaining mode hybridization due to squeeze film effects.

Findings

Resonant frequencies increase proportionally with pressure.

Damping forces are linearly related to pressure.

Mode hybridization occurs near-degenerate modes due to squeeze film effects.

Abstract

The effects of pressure on micromechanical air-filled cavities made by a pair of suspended, parallel silicon nitride membranes are investigated in the free molecular and quasi-molecular regimes. Variations of the fundamental drummode mechanical resonant frequencies and damping with air pressure are determined by means of optical interferometry. A kinetic damping linear friction force and a positive resonant frequency shift due to the compression of the fluid between the membranes are observed to be proportional with pressure in the range 0.01-10 mbars. For resonators with near-degenerate modes hybridization of the modes due to this squeeze film effect is also observed and well accounted for by a simple spring-coupled oscillator model.