Effect of Squeeze Film Damping and AC Actuation Voltage on Pull-in Phenomenon of Electrostatically Actuated Microswitch

Abstract

The effect of squeeze air-film and AC actuation voltage on dynamic stability of microswitch actuated electrostatically has been investigated in squeeze film domain. The dynamics of the device has been developed considering the load arising from the squeezed air film between the microcantilever attached plate and the grounded substrate. Using trajectories in phase plane and time history, characteristics of the pull-in phenomena have been studied in the presence of DC voltage combined with AC component. Pull-in voltage is observed to be less as compared to the conventional micro-cantilever devices which are actuated only due to DC loading. Furthermore, the dynamic pull-in voltage tends to approach static pull-in voltage, when the squeeze film damping is considered. The study indicates that although electrostatic forces cause softening characteristics, geometric nonlinearity produces a stiffening effect on the microstructure and the nonlinearities play a significant role when pull-in occurs. The ability to resist the bending deformation has become higher as the overall damping has been enhanced due to the effect squeeze film damping. The consideration of higher order nonlinearities while modeling electrostatic forces, predicts more accurate response. This research gives a desirable insight of dynamic behavior of MEMS device under the influence of squeeze film effect.