This New Cellphone Uses Such Little Power It Doesn't Need a Battery

Imagine being out and about, only to realize that your phone's battery life is running

dangerously low and there's nowhere nearby to charge it. Now imagine how liberating it could feel to not have to worry about that. A new cellphone prototype could one day provide such relief because it doesn't need a battery at all, according to a new study. The phone, a voice call-only device, is by no means the sexiest cell on the block — the calls crackle and the phone only works within a stone's throw of a computer that serves as a sort of cell tower. But how does the device work without a battery? The cellphone requires such little power — only a few microwatts rather than the 100 microwatts a smartphone uses for voice calls — that the power it does need can be collected from the environment, according to the researchers. A tiny photodiode, smaller than an adult's pinky nail, collects ambient light while a radio frequency harvester makes it possible to use energy sent out wirelessly from a homemade cell tower, called a base station. [Top 10 Disruptive Technologies]