Instead of batteries, a new cell phone harvests the few microwatts of power it needs from a different source: ambient radio signals or light.
Researchers were also able to make Skype calls using the battery-free phone, demonstrating that the prototype—made of commercial, off-the-shelf components—can receive and transmit speech and communicate with a base station.
“We’ve built what we believe is the first functioning cell phone that consumes almost zero power,” says Shyam Gollakota, an associate professor of computer science & engineering at the University of Washington and coauthor of the paper.
“To achieve the really, really low power consumption that you need to run a phone by harvesting energy from the environment, we had to fundamentally rethink how these devices are designed.”
Researchers eliminated a power-hungry step in most modern cellular transmissions—converting analog signals that convey sound into digital data that a phone can understand. This process consumes so much energy that it’s been impossible to design a phone that can rely on ambient power sources.