Large deflections of microbeams under electrostatic loads

Abstract

Electrostatic actuated microbeams are frequently encountered in micro electro-mechanical systems (MEMS). The behaviour of these devices is characterized by electromechanical coupling, due to the mutual interaction between the electrostatic field and the deflection of the structure. Besides the non-linearity due to the coupling, geometrical non-linearities due to the microstructure's large deflections can sometimes arise. In this work, a new FEM method based on a sequential field-coupling (SFC) approach is proposed, in which electrostatic loads are gradually applied to the deformed shape of the structure. The solutions are compared with those obtained by means of the best-known numerical methods available in the literature. In the case of voltage values that generate large displacements, the proposed method appears more suitable to describe the microbeam behaviour; in particular, the voltage at which instability occurs can be evaluated and post-instability solutions can also be predicted.