A comprehensive computational model is developed to study the dynamics of electrostatically-actuated micro-electromechanical system (MEMS) switches. The operation of the device involves a thin metal membrane in repeated contact with a substrate. The membrane is driven by an electrostatic force and is damped by the surrounding gas.. The coupled interaction of structure response, fluid dynamics and electrostatics must thus be solved. A unified computational framework based on the finite volume method (FVM) is developed to account for these mechanisms. The coupling between fluid, structure and electrostatics is achieved by employing the immersed boundary method (IBM). The advantage of the method is that it allows the fluid flow and electrostatics to be computed on a fixed background mesh while the solid body moves across it. Thus the effort of re-meshing is avoided, and the method potentially allows the simulation to proceed all the way to contact. A novel cell-marking scheme is applied to distinguish the solid region, fluid region and the immersed boundary (IB) region (i.e., the fluid and solid interface). Two-way interpolation is conducted on the IB region, allowing information exchange between fluid and solid. This includes the transfer of fluid and electrostatic forces to the solid surface and the solid position and velocity back to the fluid and electrostatics solution. A series of verification tests are carried out to establish the accuracy and performance of the method. The pull-in behavior of a cantilever switch and a frogleg device are predicted by the simulation.
Application of Immersed Boundary Method to Fluid, Structure and Electrostatics Interaction in MEMS
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Mathur, S, Sun, L, Das, S, & Murthy, JY. "Application of Immersed Boundary Method to Fluid, Structure and Electrostatics Interaction in MEMS." Proceedings of the ASME 2011 International Mechanical Engineering Congress and Exposition. Volume 11: Nano and Micro Materials, Devices and Systems; Microsystems Integration. Denver, Colorado, USA. November 11–17, 2011. pp. 159-170. ASME. https://doi.org/10.1115/IMECE2011-62314
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