Last week, researchers at the University of Washington announced successful tests of a battery-free cell phone.The phone harvests radio wave energy from a wireless base station (such as Wi-Fi) and converts light through miniature photo-diodes. It used very low power ( microwatts) to transmit back to the base station. As a result, the phone does not have a battery, and thus never needs to be charged.

The researchers demonstrated voice call and even skype calls using this battery-free phone.

The prototype is made completely of commercial components.

At this time, the phone must be up to 30 feet away from this special base station, and is limited only to voice communications (that require the lowest bandwidth of all phone applications today, and therefore the least amount of power).

Don't expect this phone to have a display, to provide video communications, or to have any apps. However, at a time when a smartphone needs to be charged every day, and when third-world countries lack basic utilities such as electricity, a phone that requires no charging at all could have a significant social impact.

I expect two trends to continue to make this phone viable (beyond the current 30-foot range): more efficient power harvesting, and more efficient wireless communications. Both can possibly be achieved with better base station design.

"The proof of concept we've developed is exciting today, and we think it could impact everyday devices in the future," said Joshua Smith, professor and faculty lead at the Paul G. Allen School of Computer Science and Engineering at the University of Washington, according to UW News.