A few months ago, John Goodenough, inventor of the popular lithium-ion battery, introduced the world to a newer version of the rechargeable battery he originally developed in the 1980s. With so much of the world’s manufacturers pushing newer designs for the lithium-ion battery, it was only a matter of time before those limits were pushed too far, as with the Note 7 saga in 2016. The new technology would potentially mean a lower costing, all-solid-state battery, which is noncombustible and has a much longer cycle life (battery life) and has a high volumetric energy density with fast rates of charge and discharge. All of that, however, has been eclipsed with the latest battery development by researchers at the University of Washington in Seattle who are claiming to have created a battery-free phone.
While still in prototype phase, the research is a culmination of years of work and vision by Vamsi Talla, a research associate in the field of computer science and electrical engineering at UW. The battery-free phone was built with off-the-shelf components and is able to run on a combination of wireless power and solar chargers fitted to the device. The bare bones devices are able to transmit and receive voice signals by means of connecting to a nearby base station that relays the signal to a cellular network, in this case via Skype. To use the device, the user has to push a button to talk once the call has been established. The development and research are still in its infancy and has the potential to change how we use and power our mobile devices. At this stage, however, since there is no screen or memory in use, don’t expect to use the device for anything other than to send a text or make a call, as the power requirements grow exponentially with each additional feature.
The battery-free phone generates its own signal by means of backscatter, a common practice used in RFID tags, in order to transmit radio frequencies that encode existing radio signals with additional or new information and reflects them back to the receiver. In short, the device uses radio-frequency TV and Wi-Fi broadcasts that can be converted into energy using an antenna. This technology, coupled with the use of analog voice encoding saves on power consumption of the device to transmit a call. The additional power required to increase the frequency range is done by means of photodiodes, which are essentially small solar panels. Ambient light is then turned into small bursts of electricity as a result.
In its present form, the battery-free device cannot simply connect to your local operator network to make calls and requires a custom-built basestation, which converts the commonly used digital signals from other phones to the analog signal required to be used in the experiment. The potential already exists in modern basestations but will require quite a lot of reworking of the circuitry and code. An alternative to this would be to install smaller routers in homes and work to enable it. The next steps for Talla are to improve voice quality on the calls and to include an e-Ink display. Your standard smartphone display requires more than 100,000 times the power produced on the prototype.
You can read the full research paper published on 30th June 2017.