2. Experimental nanotribology techniques

In order to make significant advances in the characterization of interfacial phenomena, we need experimental tools that enable us to work on a single contact (a single asperity) with well-controlled geometry and chemistry. Such equipment now exists. The most commonly used is the atomic force microscope (AFM). This technique enables nanometric-scale contact between a very fine tip and a substrate. A second device, less widely used, is the SFA (Surface Forces Apparatus). This device also ensures a single contact, this time microscopic in size, between two smooth surfaces on an atomic scale. The size of the contact zone makes these two techniques complementary. In a single contact, size effects on friction can come into play, particularly between molecular and supramolecular scales. A third device used for nanotribology studies is the quartz crystal microbalance (QCM).