SCREAMING at your dying cellphone battery may soon do some good, thanks to a postage stamp-sized microphone that can harvest acoustic energy to top up your charge on the go.
Zhong Wang and his colleagues created their microphone from a sheet of paper just a few centimetres across. They used a laser to zap a grid of microscopic holes in the paper, coated one side in copper and laid it on top of a thin sheet of Teflon, joining the two sheets at one edge.
Sound waves vibrate the two sheets in different ways, causing them to come in and out of contact. This generates an electric charge, similar to the one made when your rub a balloon on your hair, which can charge a phone slowly. It can also be converted into a range of sound frequencies, using the sheets as a microphone (ACS Nano, ).
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This article appeared in print under the headline 鈥淧aper microphone creates a charge鈥�