Researchers from the University of Washington have made what they believe to be the first cellphone that doesn't require a battery. Instead of drawing power from a battery, the rudimentary proof-of-concepts harvest the necessary 3.5 microwatts of power from light using tiny solar cells, or from ambient radio signals.
Made of commercial, off-the-shelf (COTS) components, the phone works by placing calls through Skype. To make a call, the user enters the number and the phone transmits the information to a base station. The base station places the call via Skype, and the phone receives the signal and plays the audio through earbuds. The base is also responsible for supplying the ambient power, as long as it's less than 31 feet away, that the cellphone uses to harvest energy.
Why hasn't this been done before? Because, until now, designers haven't been able to convert sound into digital data that the phone can understand without chewing up too much power.
These researchers are using the tiny vibrations in a phone's microphone and speaker to transmit speech in a way that uses almost no power.
The team of electrical engineers and computer scientists are now trying to improve the phone's operating range and make these conversations more secure. They are even trying to transmit video calls using E-ink screens.