Battery-Free Cell Phone Prototype Sounds Too Good To Be True

For most of us, a battery-free phone would be an unfathomable dream come true. Imagine being able to use your iPhone 7 or Galaxy S8 all day, everyday without worrying about charging it. Well, researchers from the University of Washington have made the first step, albeit a very tiny one, towards making that a reality. They've managed to create a prototype cell phone that operates without the use of a battery.

The tiny little device — which resembles little more than a circuit board — runs on just 3.5 microwatts of juice, and uses a solar cell that's "roughly the size of a grain of rice" to draw ambient power from surrounding light and radio signals. These signals are produced by a special base station that sits about 50 feet away.

The researchers say the conversion of analog audio into digital data is the most energy-consuming part of a normal cell phone, and to get around this, their prototype's microphone and speaker use small vibrations to encode the incoming and outgoing signals. There's no fancy screen, but the phone uses capacitive touch buttons to dial and place a call, with their demo showing a call being received via Skype.

The trade-off is that it can't send and receive audio at the same time, so it functions a bit like a walkie-talkie where the user must press and hold a specific button to either talk or listen to the other caller.

Of course, the researchers plan to continue developing their prototype and hope to add features like an e-ink screen and encryption for secure calls. They imagine battery-free phones becoming ubiquitous one day by placing the base station technology in things like cell towers and WiFi routers, in turn allowing coverage to be available almost everywhere.

SOURCE University of Washington