researchers at the university of washington have developed an innovative way of avoiding potential fires in cell phone batteries – they removed the battery. the new phone harvest microwatts of power from ambient radio signals or from light, according to a report on the university website.
the university of washington created a battery-less cell phone. (university of washington/youtube)
“the team also made skype calls using its battery-free phone,” the article explained, “demonstrating that the prototype made of commercial, off-the-shelf components can receive and transmit speech and communicate with a base station.”
in order to limit the power needs of the cell phone, the researchers removed the necessity for converting analog signals into digital data that the phone understands. instead, the phone uses the tiny vibrations in the microphone or speaker and converts them through an antenna into a standard analog radio signal.
“to transmit speech, the phone uses vibrations from the device’s microphone to encode speech patterns in the reflected signals,” the article added. “to receive speech, it converts encoded radio signals into sound vibrations that that are picked up by the phone’s speaker.”
a prototype device required pressing a button to switch between transmitting and listening. with only off-the-shelf components, the research team created a phone with basic functionality such as transmitting speech and data via buttons and receiving, dialing out, and putting on hold skype calls.
while the team created a novel base for receiving and sending radio signals, the researchers believe this could be integrated into a standard cellular network or work through wi-fi.
the power budget for the prototype was only 3.5 microwatts. it could gather ambient radio signals from a base that was up to 31 feet away or could get energy from a small solar cell, about the size of a grain of rice, and communicate with a base that was 50 feet away.
the research was published in proceedings of the association for computing machinery on interactive, mobile, wearable and ubiquitous technologies. the abstract stated:
“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 base station. this we believe is a major leap in the capability of battery-free devices and a step towards a fully functional battery-free cellphone.”
see the battery-free phone in action in the video below:
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