The project was built by researchers at the University of Washington. The potentially breakthrough technology opens the door to new kinds of life-saving communications equipment during blackouts or times of disaster.
The phone can create electricity from the tiny vibrations that occur in a microphone or speaker when you’re talking on the phone. The vibrations are converted into changes in analogue radio signals that are then sent to a cell tower.
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The system allows the phone to encode voice data for transmission using the energy created by your speech. The solution side-steps a regular cellphone’s energy-intensive digital-to-analogue conversions entirely.
The power produced is sufficient to power a set of off-the-shelf radio transmission components that allow it to communicate with cell towers. It can transmit voice signals over existing protocols, including services that are usually associated with apps and the internet.
In the current prototype, calls are made using Skype. The user has to press a button to switch between the “listening” and “transmitting” modes, similar to old walkie-talkies. The researchers have successfully made and received calls using the device, illustrating the potential of the concept.
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If the phone is commercialised, it could help people in regions with unreliable power supplies to stay connected. The device could also be distributed among the population in areas at risk of natural disasters. It may help to keep communication lines open when electricity supplies are unavailable.
There are still a few challenges to solve though. The power generated by vibrations alone isn’t sufficient to maintain a connection to a distant base tower. The prototype includes two alternative power sources to extend its range, a tiny solar cell and a mechanism that lets it harvest ambient radio signals.
Even with these additional power sources, the phone is still restricted to a 50-feet radius from its tower. This limitation could restrict its viability as a serious communication aid. The researchers are already tackling the issue but said they’re having to “fundamentally rethink” how devices are powered. Only 10 microwatts can be generated from the air, around five orders of magnitude less than the 3 watts a phone might demand.
“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,” said research co-author Shyam Gollakota.
“Real-time phone operations have been really hard to achieve without developing an entirely new approach to transmitting and receiving speech,” added fellow co-author Bryce Kellogg.
It is possible the device could evolve into a usable phone with some more development. It’s based on regular radio hardware and off-the-shelf electronics components, making commercialisation relatively simple. The team is planning to improve the phone’s range and add encryption capabilities as its next aim. Beyond that, the researchers want to investigate streaming video to a battery-less device.
