Fluid damping in compliant, comb-actuated torsional micromirrors

Fluid damping is studied for resonant torsional micromirrors, electrostatically actuated by comb fingers. A three-dimensional computational fluid dynamics (CFD) model of the air flow around the moving parts of the mirror is developed, coping with dynamic remeshing procedures to properly account for the large displacement setting required by the motion of the compliant structure. The time evolution of the damping torque contributions, due to shear at comb fingers and to drag over the surfaces of the micromirror plate, are computed. The relevant numerical estimation of the overall quality factor of the system is shown to compare well with available experimental results.