Two fixes for nanoscale friction

Machine parts in sliding contact are subject to friction and wear that limit their lifetimes. The problem can be especially severe in miniature devices consisting of micrometer- and nanometer-sized gears, actuators, and other moving parts, because conventional types of lubricants tend to be unusable in those devices. Surface erosion in microscopic machine components quickly ruins such devices. Now, two research teams, each using atomic force microscopy techniques, have demonstrated novel methods for controlling friction in nanometer-scale contact regions (Science 2006, 313, 186 and 207). In one study, researchers at the University of Basel, in Switzerland, and McGill University, in Montreal, show that friction can be switched on and off by applying a small vibrating force to the contact interface. Another type of "on-off switch" has been demonstrated by scientists at Lawrence Berkeley National Laboratory and Ames Laboratory, in Iowa. In that study, the researchers show that friction on semiconductor surfaces can be controlled with electric fields by applying a bias of just a few volts.