Cellphone that works without batteries is now a reality

Scientists, including those of Indian origin, have developed a new battery-less cell phone for the first time that consumes almost zero power and runs by harvesting energy from ambient radio signals or light.

The team also made Skype calls using its battery-free phone, demonstrating that the prototype made of commercial, off-the-shelf components can receive and transmit speech and communicate with a base station.

We have built what we believe is the first functioning cell phone that consumes almost zero power," said Shyam Gollakota, associate professor at the University of Washington (UW) in the US.

Researchers eliminated a power-hungry step in most modern cellular transmissions - converting analogue signals that convey sound into digital data that a phone can understand.

This process consumes so much energy that it has been impossible to design a phone that can rely on ambient power sources, researchers said.

Instead, the battery-free cell phone takes advantage of tiny vibrations in a phone's microphone or speaker that occur when a person is talking into a phone or listening to a call.

To transmit speech, the phone uses vibrations from the device's microphone to encode speech patterns in the reflected signals. To receive speech, it converts encoded radio signals into sound vibrations that that are picked up by the phone's speaker.