Bi-stability of two coupled functionally graded plate-type MEMS under opposing differential pressure

Artikel i vetenskaplig tidskrift, 2025

Snap-through instability, normally observable in initially curved micro-plates, can be utilized as a sensing mechanism. Given the higher stiffness of curved structures in comparison to flat ones, this mechanism faces a serious limitation of low sensitivity. It has recently been shown that pressurized flat micro-plates are able to face snap-through instability and benefit from high sensitivity. Therefore, the present paper aims to investigate the bi-stability of two pressurized electrostatically coupled flat micro-plates for the first time. The micro-plates are both made of functionally graded materials, and the influences of small scales are accounted for based on the modified couple stress theory. Adopting a Galerkin-based two-degree-of-freedom reduced order model containing thirty-eight approximating functions, equilibrium, stability and free vibrations of the system are assessed. The convergence of the generated ROM is studied and its outcomes are validated by those simulated in COMSOL Multiphysics as well as the results available in the literature. Aside from the expectable simultaneous pull-in instability, where the electrodes stick to each other at the pull-in state, the results also illustrate a new and interesting unstable behavior where the micro-plates with different thicknesses experience snapping behavior simultaneously.