Cellphone Harvests Power From Ambient Radio Signals And Light
A new cellphone has been created by team of computer scientists and electrical engineers at the University of Washington. The battery-free phone harvests power from either ambient radio signals or light.
(Battery-Free cellphone video)
We present the first battery-free cellphone design that consumes only a few micro-watts of power. Our design can sense speech, actuate the earphones, and switch between uplink and downlink communications, all in real time.
Our system optimizes transmission and reception of speech while simultaneously harvesting power which enables the battery-free cellphone to operate continuously. The battery-free device prototype is built using commercial-off-the-shelf components on a printed circuit board. It can operate on power that is harvested from RF signals transmitted by a basestation 31 feet (9.4 m) away.
Further, using power harvested from ambient light with tiny photodiodes, we show that our device can communicate with a basestation that is 50 feet (15.2 m) away.
Finally, we perform the first Skype call using a battery-free phone over a cellular network, via our custom bridged basestation. This we believe is a major leap in the capability of battery-free devices and a step towards a fully functional battery-free cellphone.
The idea that devices could be powered just from remotely-radiated power sources fascinated inventors of the early Twentieth century. The idea that power could be harvested from ambient sources is a bit more recent.
Science fiction writers of that period were also fascinated. Robert Heinlein used the idea in a fanciful way in his 1942 novella Waldo; see the entry for radiant power receptors.