Mobile phone batteries, no matter how good they get, are still the Achilles heel of any phone. That is, except for a mobile phone prototype created by researchers at the University of Washington, built to work on an unimaginably small amount of power.

The super-efficient phone doesn't so much sip power as breathe it in from the air around it. It asks for just 3.5µW of power. That's microwatts, kids. The device gets its power from a base station 31 feet away via RF signals. A tiny photodiode can pull in ambient light to extend that range to 50 feet. The phone connects to that base station which makes a call via Skype and communicates via zero-power amplitude modulation.

It ain't pretty

What they have here is a very basic prototype. Don't expect to see it on shelves next year or anything like that. The prototype is built with off-the-shelf parts and, for now, is just a basic circuitboard that transmits some very low-quality audio. It's a far cry from the mostly-crystal-clear audio we're used to.

But with that said, the potential of this is huge. Battery free cellphones could allow a whole village in a remote area to communicate with just one base station and no need to recharge. As audio compression gets better and researchers and manufacturers optimize the components, something like this could become truly viable.