Squeezed film damping measurements on a parallel-plate MEMS in the free molecule regime

This paper provides the first experimental validation of the predictions by two recently introduced models for free molecule squeezed film damping. Measurements were carried out using a parallel-plate microstructure with a 2.29 mum gap operated at air pressures from 10⁵ down to 10¹ Pa (corresponding to Knudsen numbers from 0.03 to 300). Experiments are in good agreement with the modeling based on molecular dynamics at low pressures. The results also indicate that modeling based on the modified Reynolds equation including inertia effects underestimates the damping due to end effects, but correctly predicts the trend at lower Knudsen numbers reaching into the transitional regime.