The team has developed a phone that uses "almost zero power" which harvests microwatts of power from RF signals transmitted from a base station that is 31 feet away.
Associate professor Shyam Gollakota, who co-authored a paper which detailed the breakthrough. said additional power is harnessed via ambient light through the use of miniature photodiodes that are about the size of a grain of rice.
While in use, the phone consumes about 3.5 microwatts of power and is capable of communicating with a custom base station that is up to 50 feet away to send and receive calls. The phone ditches the traditional analog-to-digital converter, which turns your voice into data, in favor of a system that uses the vibrations from a microphone or speaker to perform the same task. An antenna then converts that motion into radio signals in such a way that very little power is consumed.
At the moment the tech has a few problems. Modern smartphones "need a lot more than a 3.5-microwatt power budget for a blazing fast processor, RAM and internal storage, and power-hungry displays".
At the moment you also have have to press a button to switch between transmissions and listening modes with the phone.
Still it is a good start.