A research team at the University of Washington have invented a cellphone that requires no batteries. Instead, the phone harvests the few micro-watts of power it requires from either ambient radio signals or light.

Smartphones have become a critical part of modern communication and the capacity of their battery life remains an issue. Models, brands and companies compete and differentiate themselves in this space. However, many smartphone users are still unable to make it through a single day without having to seek out a charger. The challenge to improve the power autonomy of smartphones has got many innovators grinding through many technology alternatives.

One of such effort is paying off as a team of researchers from the University of Washington have developed a phone that requires no batteries. These battery-free cellphones harvest the minimal power it needs from ambient radio signals, yet can communicate with a base station to make voice calls. According to the team, their new battery-less phone consumes almost zero power. It is built on a printed circuit board using off-the-shelf components. This makes it look deceptively simple (not the iPhone featured above), but it is capable of the basic cellphone functions – send, receive, make and accept calls, and place callers on hold.


Battery Free Phone
Working Prototype
Baettery Free Phone
The research team from the UW Department of Electrical Engineering and the Allen School of Computer Science & Engineering (Photo Credit: Mark Stone/University of Washington)


Technology Highlights

  • Key here is the new approach to transmitting and receiving speech, which makes it possible for the prototype to perform basic cell phone functions. Many other battery-free technologies that rely on ambient energy sources, conserve energy with intermittent operations. They take a reading and then sleep for a minute or two while they harvest enough energy to perform the next task. By contrast, a phone call requires the device to operate continuously for as long as the conversation lasts. “You can’t say hello and wait for a minute for the phone to go to sleep and harvest enough power to keep transmitting,” said co-author Bryce Kellogg.
  • The technology eliminates a power-hungry step in most modern cellular transmissions i.e. converting analog signals that convey sound into digital data that a phone can understand. This process consumes so much energy that it’s been impossible to design a phone that can rely on ambient power sources. However, the near-zero power requirement of the prototype enables it to survive battery-less.
  • Like a walkie-talkie, the user must press a button to switch between listening and transmitting modes. To transmit speech, an antenna connected to the microphone encodes the user’s speech patterns in the radio signal reflected from the antenna, while receiving speech involves an antenna converting speech patterns encoded in the radio signals into sound vibrations that are relayed to the phone’s speaker.


There are a number of technical hurdles to overcome in bringing this to a competent everyday application. However, the team remains upbeat. They are also working on how to encrypt messages and stream videos and adding a low-power E-ink screen for a display. The researchers believe that the technology could be installed in a standard cellular network or Wi-Fi router to make calls battery-free.


See the video below:

Links: ACM, University of Washington



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