Friction mechanisms at the micro-scale

Contact between macroscopic surfaces occurs on asperities and local nano-/micro-scale asperity interactions govern macroscopic tribological behavior. Tribological phenomena like friction and wear are highly scale dependent. Friction measurement carried out in the range of micro-/milli-Newton loads are gaining prominence in the tribological research as they are bridging the gap between classical macro-scale tests and high precision nano-scale experiments. In this paper, recent advancements in micro-scale domain are discussed and compared with the existing macro- and nano-scale friction research. There exists a striking similarity between micro- and nano-scale frictional behavior of various materials and dependence of friction on capillary forces, surface topography, and phase composition of mated materials. Micro-tribological experiments not only offer precision and sensitivity of nano-scale (or LFM) measurements, but also give reliable information due to its multiple asperity contact configuration.