Analytical model of squeeze film damping for microelectromechanical systems structures with anti-stiction raised strips

Some regular raised strips are often introduced into microelectromechanical systems (MEMS) devices for avoiding the stiction between movable microstructures. An analytical model is proposed to evaluate the squeeze-film damping of MEMS suspension structure with anti-stiction raised strips by utilising reasonable boundary conditions. These raised strips cause a non-smooth pressure distribution between the moving and the fixed plates. The damping coefficients against distance between two plates with (and without) raised strips are also theoretically obtained by this analytical model. The two kinds of typical suspension microstructures have been fabricated by surface microelectroplating. Their vibration decay curves have been tested by laser detector. Calculated damping coefficients by amplitude envelopes are, respectively, about 0.34 and 0.05 N s/m when the moving plate reaches its initial position, which are in accordance with theoretical ones.