What a time to be alive! An amazing research team from University of Washington, Seattle has come up with a way to power a phone without batteries, instead using radio waves taken from thin air.
How many times haven’t your phone battery just died when you needed to make that precious phone call? New research published in Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies suggests a future where many micro devices are powered by energy harvested from the environment.
The researchers have produced a functional phone prototype that requires as little as 3.5 microwatts, which is several hundreds of thousand times less compared to the typical 800 milliwatts required for a normal phone call. They accomplished this feat with off-the-shelf components on a printed circuit board, making use of a small solar-cell the size of a grain of rice, in combination with harvesting radio signals from a special baste station.
However, that is not all; the usual process of converting sound into encoded radio signals is still far too power-hungry. Instead, Joshua Smith who is a computer science and electrical engineering researcher at UW, made use of old Cold-War tech. In 1945, the American Ambassador received a carving of the Great Seal of United States from the Soviets. Hidden inside it was an audio bug that reacted only to a specific frequency of radio waves, utilizing the energy of the radio waves to function.
“My dad was a spy in the Cold War, so I heard stories about the Great Seal bug when I was a kid,” says Smith. “I wondered if analog backscatter could be software-controlled and turned from a curiosity for spooks into a technology that everyone could use.”
Using backscattering, which essentially is sound waves vibrating an antenna on the device which in turn changes the radio waves emitted from the special base station to encode the sound, the team was able to transmit voice from the device’s tiny microphone. The base station relayed calls to and from the device via Skype, allowing the phone to communicate when within 15 meters from it. Though, backscattering is a lossy technique, more-or-less drowning your voice in radio static. Calls are carried out walkie-talkie style by pressing in a button on the device when you want to transmit voice, releasing when you want to receive.
The prototype is more of a tech demonstration than the essential hiker’s emergency-phone. However, Wi-Fi routers or GSM antennas could be fitted with the same technology, allowing tiny micro devices, not limited to phones, to operate using the radio waves as power.