Engineers at the University of Washington have designed a battery-free cellphone powered by either ambient radio signals solar power. The new device sends and receives calls with only a few microwatts of power and demonstrated its capabilities with Skype calls.
“The cellphone is the device we depend on most today. So if there were one device you’d want to be able to use without batteries, it is the cellphone,” said faculty lead Joshua Smith, professor in both the Allen School and UW’s Department of Electrical Engineering. “The proof of concept we’ve developed is exciting today, and we think it could impact everyday devices in the future.”
Smartphone companies, like Apple have been investigating how to make a smartphone or similar device solar-powered. But thus far none have made one that is, or for that matter produced a cellphone that works without a battery. Still companies and universities are investigating how to make a photovoltaic cell that’s transparent enough to use in a smartphone.
The device, which was made with off-the-shelf, commercial components, was able to communicate with a base station. The researchers published their research on July 1 in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies.
“We’ve built what we believe is the first functioning cellphone that consumes almost zero power,” said co-author Shyam Gollakota, an associate professor in the Paul G. Allen School of Computer Science & Engineering at the UW. “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 new device eliminates the step of converting analog signals into digital data, the most power-hungry step in process of transmitting sound into digital data. The new device harvests the motion created by voice in the speaker or microphone and converts it into a standard analog radio signal. The university said it encodes the speech patterns into reflected radio signals while using up to 3.5 microwaves of power—almost no power at all, including a solar cell the size of a grain of rice.
The device could herald a new transmission technology for cell phones while also making them more likely to be solar powered. “You could imagine in the future that all cell towers or Wi-Fi routers could come with our base station technology embedded in it,” said co-author Vamsi Talla, a former UW electrical engineering doctoral student and Allen School research associate. “And if every house has a Wi-Fi router in it, you could get battery-free cellphone coverage everywhere.”
Looking ahead the research team will focus on improving the battery-free phone’s operating range—it’s currently at about 50 feet—and encrypting conversations to make them secure. The team also wants to stream video over a battery-free cellphone.
The National Science Foundation and Google Faculty Research Awards funded the research.Tweet