A battery free cell phone: Know how it works

A team of researchers from the University of Washington has created a battery-free cell phone prototype.

Charging the smartphone's battery is an issue, no matter how many new technologies emerge to aid the cause. Your phone will get out of charge and there is no way of giving your smartphone eternal power unless there is no battery included in the phone but that's impossible right? Well, not anymore. Researchers at the University of Washington (UW) have invented a phone that doesn't need a battery to work. It harvests the few microwatts of power that it requires from either ambient radio signals or light.

battery free phone

The researchers published the detailed paper in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies. It definitely marks a huge leap forward, which has the potential to end the era of chargers, cords and dying phones.

The team of researchers included computer scientists as well as electrical engineers. They eliminated a power-hungry step in the cellular transmissions, which is converting the analog signals into digital data that can be comprehended by a phone. The said process consumes so much energy that it was impossible to design a phone that can depend on ambient power sources.

The new technology here, on the other hand, makes use of the tiny vibrations in a phone's microphone or speaker that occur when a person is talking on a phone and listening to the other caller as well.

battery free phone

An antenna connected to those speakers and microphone converts that motion into standard analog radio signal emitted by a cellular base station.

The said process essentially encodes speech patterns, which get reflected in the radio signals in a way that uses almost no power. To transmit speech, the phone uses vibrations from the device's microphone to encode speech patterns in the reflected signals and to receive speech; it converts encoded radio signals into sound vibrations, which are picked up by the phone's speaker.

In the prototype device, the user presses a button to switch between the "transmitting" and "listening" modes.

battery free phone
The team of researchers washington.edu

"We've built what we believe is the first functioning cell phone that consumes almost zero power. To achieve the really, really low power consumption that you need to run a phone by harvesting energy from the environment, we had to fundamentally rethink how these devices are designed." said co-author Shyam Gollakota, an associate professor in the Paul G. Allen School of Computer Science & Engineering at the UW.

However, the phone still requires a minimum amount of energy to perform certain tasks. The prototype has a power budget of 3.5 microwatts.

According to the news release from the UW, the researchers are now focusing on improving the battery-free phone's operating range encrypting conversations to make them secure.