Effect of Pressure and Squeezed-film Damping on Transient Response of a Double-Bridge Micromirror for Multiobject Spectroscopy

This paper presents an analytical approach to envisage a suitable operating pressure and investigate the effect of squeezed-film damping on the transient response of a micromirror of size 200 μm × 200 μm and a deflection of 2.5 μm for space-based multiobject spectroscopy. While most MEMS devices are vacuum packaged to achieve a high Q and fast switching, the same may not be true for applications that are prone to vibrations and shocks. At small pressures, the micromirror can produce undesired deflections and oscillations, and hence, a high-pressure operation becomes necessary to alleviate these effects.The operating pressure and its effect on the transient response of the micromirror are investigated by solving linearized Reynold’s equation and dynamic equation of motion using the numerical iteration method. The result shows an overdamped response above 10 kPa pressure. At 101 kPa, the micromirror exhibits a switching and release time of 102 μs and 95 μs, respectively. The analytical results are very close to the FEM results with a deviation of 8%. The result shows that operating a micromirror at atmospheric pressure serves the dual purpose of dispensing away with the requirement of vacuum packaging and providing immunity from vibrations and oscillation.