Nanotribology

Abstract

Friction, lubrication, wear, and adhesion are all phenomena familiar from everyday experience. We experience friction when we go for a walk on ordinary ground—we do not expect to fall flat on our faces, as we might when walking on ice. Wear is particularly well known because it leads to catastrophic failure and represents one of the most costly problems facing industry today. These phenomena are part of the field of tribology—the science of interacting surfaces in relative motion. A macroscopic understanding of tribology is crucial for the design and engineering of mechanical components. As dimensional tolerances of these components approach the nanometer scale and novel new materials are used in their fabrication, macroscopic understanding must give way to a microscopic atomic-scale understanding. This fundamental microscopic understanding and its practical application remain limited.With the advent of surface proximity probes, however, those limitations are rapidly disappearing. Researchers are now able to test and develop a microscopic understanding of such tribological phenomena as boundary-layer lubrication and asperity-surface interactions—ideas that underlie our current macroscopic understanding. This emerging field is known as nanotribology or molecular tribology, the focus of this issue of the MRS Bulletin. The new experimental probes include the surface force apparatus for measuring interfacial forces as a function of surface separation and, more recently, rheological properties of molecularly thin layers; a quartz-crystal microbalance for measuring the atomic-scale friction of adsorbed monolayer films; and the atomic force microscope (AFM) for measuring nanomechanical properties of surfaces, atomicscale friction of clean surfaces, and frictional properties of surfaces coated with molecular films.