Asperity-Based Models of Micro-Scale Friction

As surfaces become smoother and loading forces decrease in applications such as MEMS, NEMS, and magnetic recording devices, the size and number of the asperity contacts which comprise the real contact area continues to decrease. The tangential force which is measured between two sliding bodies is the combined result of friction forces which are present in a very large number of nano and micro scale asperity contacts. Recent experiments as well as modeling have shown considerable scale-dependence and nonlinear load-dependence of the friction force. These models will be reviewed and discussed.