Nanotribology and MEMS

The tribological phenomena of adhesion, friction, and wear arise when solid objects make contact. As the size of devices shrinks to micro- and nanoscales, the surface-to-volume ratio increases and the effects of body forces (gravity and inertia) become insignificant compared with those of surface forces (van der Waals, capillary, electrostatic, and chemical bonding). In microelectromechanical systems (MEMS), tribological and static interfacial forces are comparable with forces driving device motion. In this situation, macroscale lubrication and wear mitigation methods, such as the use of bulk fluids and micrometer thick coatings, are ineffective; new nano-engineering approaches must be employed for MEMS devices with moving structures. We review fundamental tribological problems related to micro- and nanoscale mechanical contacts and developments in MEMS lubrications.