On the response of a resonating plate in a liquid near a solid wall

We investigate the effect of a nearby solid wall on a microfabricated resonating plate immersed in a fluid. This phenomenon, known as squeeze film damping, has long been studied with microfabricated devices in gases but only recently with incompressible liquids. Here, we make measurements with a rectangular plate operating in its fundamental resonance mode in close proximity to a solid wall in a wide range of fluid viscosities (1–50 cP). For the plate oriented parallel to the wall, we measure power law-like behavior for the dependence of both the effective mass and the drag experienced by the sensor as a function of wall distance (−1/2 and −1, respectively). For the plate oriented perpendicular to the wall, we discover the surprising result that each viscosity has a unique distance of maximum damping.