Researchers have developed a cell phone that pulls energy from the world around it, allowing it to operate without any battery at all.
The remarkable prototype relies on a technique known as backscatter, in which the device can reflect radio waves to communicate.The prototype basestation uses an unlicensed frequency, limited to low-power transmissions. Because the phone relies on those signals for its energy harvesting, it has a range of just 15 meters from the basestation.The phone has a basic touch-sensitive number pad and its only display is a tiny red LED that glows briefly when a key is pressed.