Imagine never having to charge your smartphone ever again. We may be one step closer to that battery-free future thanks to new research from University of Washington engineers. They made a phone capable of calling people using energy from light and ambient radio signals. Associate professor Shyam Gollakota said they think it could be the “first functioning cellphone that consumes almost zero power.”

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No, it’s not magic – the University of Washington’s battery-free cellphone can function on just a few microwatts of power it harvests from RF signals coming from a base station around 31 feet away, or from light via a minute solar cell that’s about the size of a grain of rice. The team constructed their prototype from off-the-shelf components and have already used it to make Skype calls.

Related: MIT’s New Battery-Free Chip Captures Energy From Light, Heat, And Vibrations at the Same Time

The cellphone prototype is able to run on such low power in part because the team got rid of the step to convert analog signals into digital data – a process that sucks up a lot of power in modern cellphones. Their battery-free phone can make use of small vibrations from the speaker or microphone that come when a person is talking or listening while making a call.

According to a university press release, “An antenna connected to those components converts that motion into changes in standard analog radio signal emitted by a cellular base station. This process essentially encodes speech patterns in reflected radio signals in a way that uses almost no power.”

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The team designed their own base station to receive and transmit radio signals. But that technology could be embedded in cell towers or even Wi-Fi routers in the future. Research associate Vamsi Talla said if every home has a Wi-Fi router – as many already do – “you could get battery-free cellphone coverage everywhere.”

The research was recently published in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable, and Ubiquitous Technologies. The team plans to keep working on the technology to increase the operating range and encrypt conversations. They also aim to stream video on battery-free cellphones.

+ Battery Free Phone

Via the University of Washington

Images via Mark Stone/University of Washington