CFD Analysis of Aerodynamic Drag on Resonating MEMS Micro-Scanners

Computational fluid dynamic (CFD) simulations of the flow induced by a MEMS circular micro-mirror plate undergoing out-of-plane oscillatory rotation are performed. Pressure and viscous contributions to the aerodynamic drag acting on a 1 mm diameter plate are evaluated for a range of scanning frequencies (2 max (°) < 20). Results show that flow separation and inertia effects are significant within the typical operating region of resonant micro-scanners. In this region of operation, a quadratic increase in damping moment with scan frequency and amplitude is observed. The variation of the cycle-averaged drag coefficient with respect to the Reynolds number is presented, providing an accurate representation of air damping in the design process of resonant micro-scanners. The dependence of air damping on thickness of the micro-scanner layer and depth of the underlying cavity is also investigated.