Modeling Multiscale Contact in MEMS

A model is presented to investigate contact and friction between sliding microelectromechanical systems (MEMS) surfaces. Roughness of MEMS surfaces exhibits multiscale structure. This was observed with analysis of asperities on atomic force microscope (AFM) images of real MEMS surfaces. The contact model is developed using multiple scales of surface roughness, with a single asperity contact model for the behavior of an asperity at a particular length scale, including effects such as surface forces (adhesion). The roughness information for the model is obtained from the AFM image of the MEMS surface under consideration. Results for true contact area and a prediction of the macroscopic coefficient of friction are discussed.