Air damping of microbeam resonators in a low vacuum

This paper presents a theoretical and numerical study of air damping of microbeam resonators oscillating in a low vacuum. Particular focus is on air flows that are in the free-molecule regime. First, a careful review of previous theoretical studies was conducted.. Limitations and errors associated with these studies have been pointed out. In particular, we have found the assumptions used in some studies, in which analytical expressions are derived, lead to an over-predicted quality factor (by a factor of two). A molecular dynamics (MD) code was then developed and used to predict and study air damping of a microbeam resonator oscillating vertically in a low vacuum. A very good agreement with experimental measurements in the low pressure range has been obtained. The effects of important parameters such as oscillation frequency and amplitude on the quality factor were also investigated.