How a crying baby might soon power your phone

Acoustic energy would give you a juice boost

This microphone will charge your mobile

Nanotechnologists at the Georgia Institute of Technology have made a microphone out of paper that could boost phone battery life using 'wasted' sound energy.

The team, led by Zhong Wang, used a laser to burn miniscule holes in a sheet of paper the size of a postage stamp, then coated one side in copper and the other with polytetrafluoroethylene - better known outside the chemistry world as the coating on non-stick pans. The two sides were joined on one edge, but left free on the others.

Sound waves, as you might remember from your physics classes, are made up of vibrations in the air. As they hit the sheet of paper, they cause the copper and Teflon sides to come into and out of contact, generating a small amount of static electricity like rubbing a balloon on your head.

Sounding good to us

That electricity - about 121 milliwatts per square metre - can then be harvested and used for whatever you like. Wang suggested its use in a mobile phone, but the trickle of power is far too low to charge most modern handsets - it'd merely extend battery life a small amount instead.

Still, Wang also suggests it could be used in military surveillance, sound recording, or jet engine noise reduction.

Us? We'd like to see it used to power a pair of noise-cancelling headphones so the screaming child two rows behind us on a plane is actually doing something useful.

The team's research was published in ACS Nano.

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