Analysis of static charge induced pull-in of an electrostatic MEMS

Abstract

Electrostatic actuation of micro-structures is largely affected by static charges, leading to its unpredictable behavior. Microstructures mainly accumulate static charges during fabrication, handling and operation. Moreover, microstructures are also actuated by charge-voltage combinations to improve its performance, i.e., increasing travel range. In this article, a distributed parameter model of microbeam, actuated by charge-voltage combinations, is presented. The proposed non-linear model is used to study the effect of static charge on the pull-in of three microstructures, namely cantilever, clamped-clamped, and complementary fixed-free microbeams. Closed-form expressions of pull-in voltage for different configurations are derived as a function of the surface charge density over the microbeam. The numerical solutions of the proposed model are also validated using finite element analysis based COMSOL Multiphysics simulation. Finally, the application of the proposed model for microbeam actuation using partial-electrode for detection of label-free DNA is also presented.