Battery-free smartphone dials up new possibilities

Researchers have made Skype calls from the battery-free phone.

Despite remarkable advancements in smartphone technology in recent years, poor battery life remains one of the most unavoidable frustrations for modern devices.

Manufacturers have attempted to solve the issue with large, lithium-ion batteries and adaptive fast charging, but this has only offered mild success.

In an attempt to deliver a long-term solution, researchers at the University of Washington are exploring what happens if we remove batteries from smartphones altogether.

Before you discredit the concept as pointless, it is probably worth noting the team has already been able to develop a battery-free phone built entirely from off-the-shelf materials on a printed circuit board.

Associate computer science and engineering professor Shyam Gollakota said the team had been able to prove the technology worked by making Skype calls from the battery-free phone.

"We've built what we believe is the first functioning cellphone that consumes almost zero power," Gollakota told UW Today.

"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."

The phone currently works by harassing power from radio frequency signals sent by a nearby custom base station and through the use of photodiodes -- a semiconductor device that converts light into an electrical current.

Computer scientists and electrical engineers started by figuring out how they can eliminate the need for the phone to convert the analog signals that convey sound into digital data -- one of the most energy consuming processes in modern cellular transmissions.

The solution was encoding speech patterns in reflected radio signals by taking advantage of the tiny vibrations heard when a person is talking or listening on the phone.

Essentially, vibrations from the device's microphone encoded speech patterns in the reflected signals to transmit sound, while vibrations from the phone's speaker were used to receive speech.

While the team had to design a custom base station to transmit and receive these radio signals for the purpose of the test, they believe the same result could be achieved by standard mobile network infrastructure or Wi-Fi routers.

"You could imagine in the future that all cell towers or Wi-Fi routers could come with our base station technology embedded in it," explained team member Vamsi Talla.

"And if every house has a Wi-Fi router in it, you could get battery-free cellphone coverage everywhere."

To allow the device to work from further away from the base station, tiny solar cells have been used to harvest power from ambient light.

But more work needs to be done.

The team is also working on video streaming and adding a visual display feature to the phone using low-power E-ink screens.