Analytical and computational modeling of viscothermal acoustic damping in perforated microstructures

摘要

Predicting the viscothermal acoustic behavior of microstructures is crucial in the design of micro-electro-mechanical systems (MEMS). In MEMS structures the dimensionless shear wave-number is typically smaller than one. Therefore, the viscous effects are larger than inertial effects and are the dominant part of the impedance. In this work, an analytical solution for the viscothermal acoustic impedance for perforated microstructures used in MEMS devices is developed based on the low reduced-frequency (LRF) method. This solution is based on a full-plate approach, as opposed to the single-cell approach, which includes all viscous and thermal losses as well as compressibility and inertial effects. Additionally, a 3D viscothermal acoustic model using the finite element method (FEM) is developed to solve the problem numerically for the case of a MEMS microphone. The results of the analytical LRF solution are in good agreement with the FEM results. The results can be applied in designing MEMS devices to minimize the damping and to optimize the acoustic performance of the MEMS devices.