Scanning probe microscopy measurements of friction

This article describes the details of scanning probe microscopy measurements of interfacial friction from an experimental perspective. In such studies, the probe tip is taken as a model of a single asperity within a tribiological contact, and interfacial forces are measured as function of the sliding contact of the probe tip with the surface. With appropriate detection schemes, friction and load forces can be monitored simultaneously and used together to describe the frictional properties of the microscopic contact. This article provides a detailed description of the procedures and protocols of friction measurements performed with scanning probe microscopy, the relevant properties of probe tips, and the influence of envoirnment on microscopic friction measurements. In addition, this article provides a brief overview of several categories of friction studies performed with scanning probe microscopy, highlighting the type of materials characterized in these studies as well as the importance and impact of the microscopic measurements.