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Energy from friction

Device demonstrates the electricity produced when two materials are rubbed together

INERTIA FILMS /GEORGIA TECHDevice demonstrates the electricity produced when two materials are rubbed togetherINERTIA FILMS /GEORGIA TECH

The little shock that almost all of us have felt when we touched an object, especially a metal one right after walking across a carpet on a cold, dry day, is produced by a kind of energy that researchers at Georgia Tech are now using to develop generators that can recharge smartphones and run self-powered sensors. The scientists rely on tribology, the science that studies friction, wear, and lubrication. The triboelectric nanogenerators currently being designed feed off the exchange of electrons that occurs between two materials when they are rubbed together, with one donating and the other accepting the electrons. The continuous repetition of this process produces a small current that can be harvested by electrodes installed on the device. There is nothing new about the process but these scientists, led by Prof. Zhong Lin Wang, have innovated the way the two materials are separated in order to take greater advantage of the current flow. The new process relies mainly on sheets of polymer, but fabric and paper are also used. Since launching this research, the team has managed to boost the power output density of their triboelectric generator by a factor of 100,000. The study was published in the journal ACS Nano in November 2013.