Numerical Studies of the Squeeze-Film Damping of MEMS Devices with Perforations in the Non-Continuum Regime

Predicting squeeze-film air damping of resonators in rare air is crucial in the design of high-Q devices for various applications. In the past, there have been two approaches to treat the squeeze-film air damping in non-continuum regime: using effective viscosity coefficient and using the molecular dynamics method. And most of the previous work focused on devices in which the rarefaction effects of air are not significant. For such cases, continuum theory is often adequate. However, we have investigated the air damping on oscillating structures in the free molecular regime in which classical continuum theory is no longer valid. Based on this premise, Hutcherson (2004 J. Micromesh. Microeng. 14 1726-1733) has developed a molecular dynamics simulation code and used in predicting quality factors of an oscillating micro-plate at low pressures. However, his work is valid only for non-perforated micro-plate. This paper, a brief description of the molecular dynamics method is presented first. Then a molecular dynamics simulation code has been developed and used in predicting quality factors of a perforated oscillating micro-plate in free molecular regime. And we have found that the molecular dynamics simulation results have shown an excellent agreement with the experimental data of Kwok et al. Finally, the limitations of the present molecular dynamics simulation code have been reported.