Damping in vertical comb-drive microactuators at different pressures
摘要
Damping is a key factor affecting the dynamic performance of micro-electro-mechanical systems (MEMS) and the precise prediction of the damping behaviour is very crucial for optimizing the design and enhancing the performance parameters of MEMS based vertical comb-drive (VCD) micromirrors. The present study provides a brief discussion of various damping mechanisms in MEMS based devices especially for the VCD micromirrors. To understand the effect of damping in VCD micromirrors, Rayleigh damping and squeezed film damping (SFD), were first modelled using the finite element method (FEM). It was found that SFD is the most dominant damping mechanism to analyse the damping behaviour in VCD. Following the comparison, to comprehend the effect of SFD in VCD micromirror, FEM is used to model the SFD fluid dynamics within the narrow gap of 400 μm for various flow regimes characterized by Knudsen number (Kn). The optical deflection angle and SFD film pressure distribution are calculated for pressures varying from low vacuum (1 Pa) to atmospheric pressure (105 Pa). The optical deflection angles are enhanced by upto 2.3 times while operating the device at lower vacuum (1 Pa) in comparison to the atmospheric pressure (105 Pa) and significantly reduces the input power for driving the micromirror in low pressure environment.