Researchers at the University of Washington have built a phone that does not require a battery.
Their research, published in Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, describes their device, which runs on wireless radio frequency power and tiny solar chargers. The phone has very few features: it can make phone calls and support headphones. Thus far, there is no screen or storage, and you have to push a button to talk—much like a walkie-talkie.
The researchers explain that much of what drains our phone’s battery are systems running behind the scenes. When you place a phone call, the sound wave generated by your voice is converted to a digital signal. The receiver’s phone then takes that digital signal and converts it back to analog so the listener can hear. This process takes a lot of power, which is why your phone needs substantial battery life.
The battery-free phone created by the team in Washington foregoes this process by creating a custom-designed base station to convert the signals from digital-to-analog and back again. Even though a base station is handling the conversion, the new phone still requires a 3.5 microwatt power source. What makes this phone so unique is that, instead of using a battery, the team was able to create a device that drew power from the ambient environment. The power can be drawn from a rice-sized solar cell on the phone’s circuit board.
The team also says no new base stations will need to be built, as their technology can be integrated into existing cellular networks and WiFi routers. The phone is still in an early form, so it will not hit shelves any time soon. The prototype was able to use Skype to make phone calls. Phone numbers were entered with touch buttons, and users had to switch between talk and listening modes with a button. Currently, calls can only be made within 31 feet of the base stations when using radio frequency signals and within 50 feet when using solar power.
While the technology may not be in your next iPhone, this type of research is getting us closer to a phone that never dies.