New paper microphone may help charge your phone

Washington: Running out of battery? Yell at your phone to charge it!

Scientists have developed a postage stamp-sized microphone out of paper that could boost your phone's battery using sound.

Researchers at the Georgia Institute of Technology used a laser to zap a grid of microscopic holes in the paper, then 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, 'New Scientist' reported.

This generates an electric charge, similar to the one made when a person rubs a balloon with hair, which can charge a phone slowly.

The microphone could also be used as a way to recycle sound energy from the environment, getting free electricity from the "waste" sounds all around us.

The charge can also be converted into a range of sound frequencies, allowing the initial sounds to be amplified.

The amount of power the microphone provides depends on its size, but it is around 121 milliwatts per square metre.

"It can be made into any size you like," said Zhong Wang of the Georgia Institute of Technology.

However, Wang said a stamp-sized microphone fitted to the phone would only provide a small amount of power rather than fully charging the phone.