The physics of surfaces
The physics of friction is one part of a major interdisciplinary area of science, known as tribology, which is concerned with the mechanical and electronic characteristics of surfaces.
Activity in this area has grown dramatically with the advent of microscopes (the Scanning Tunneling Microscope, and the Atomic Force Microscope) which provide atomic-level-resolution images of surfaces. The above AFM image shows a portion of a surface of diamond. The protruding chunks (‘asperities’) control the nature of contact with other surfaces...and thus the frictional force.