Never again worry about whether you have enough battery left to continue the day or if you have put in a backup battery? A team of researchers from the University of Washington (USA) has invented a mobile that does not require batteries. Instead, the phone harvests the few microwatts of power it requires to function from radio signals or ambient light . The invention has been published in the journal Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies.
To test the effectiveness of the prototype and that it can receive and transmit voice and communicate with a base station, the researchers made several Skype calls using this battery-free mobile made of commercial components.
“We have built what we believe to be the first mobile phone to consume almost zero energy. To achieve the extremely low power consumption you need to operate a phone by harvesting energy from the environment, we fundamentally had to revolutionize the way mobile phones devices are designed, “explains Shyam Gollakota, co-author of the work.
To get the phone to consume almost no power, they had to eliminate the process of converting analog signals that transmit sound into digital data that most smartphones have. “This process consumes so much energy that it has been impossible to design a phone that can rely on ambient energy sources, ” says Gollakota.
How does it work then?
The battery-free mobile phone takes advantage of the small vibrations in the microphone or speaker that occur when someone is having a conversation on the phone or listening to a call. An antenna converts those vibrations into changes in the standard analog radio signal emitted by a mobile base station. This process essentially encodes the speech patterns in radio signals in a way that uses almost no power. The only amount of power required for some operations is 3.5 microwatts
To receive calls, the phone converts encoded radio signals into sound vibrations that are captured by the phone’s speaker. In the prototype device, for example, the user presses a button to switch between ‘streaming’ and ‘listening’ modes. Investigators received incoming calls, dialed and put calls on hold with Skype.
“The mobile phone is the device that we depend on the most today. So if there was a device that we would want to be able to use without batteries, it is the mobile phone. The proof of concept that we have developed is exciting today, and we think it could affect everyday devices in the future, “says Joshua Smith, co-author of the paper.
The technology used by the experts could be integrated into the standard mobile network infrastructure or Wi-Fi routers so widely used today to make calls.
“You could imagine in the future that all mobile towers or Wi-Fi routers could come with our base station technology embedded in it. And if every house has a Wi-Fi router in it, you could get mobile phone coverage without battery everywhere “, clarifies Vamsi Talla, co-author of the work.
At the moment, the prototype battery-free phone can run on energy harvested from environmental radio signals transmitted by a base station at some distance. Using energy harvested from ambient light with a small solar cell – about the size of a grain of rice – the device was able to communicate with a base station that was 50 meters away.
“The amount of power that you can actually get from ambient radio or light is on the order of 1 or 10 microwatts. So real-time telephony operations have been really difficult to achieve without developing a totally new approach to transmitting and receive a voice “, concludes Bryce Kellogg, co-author of the work.
Referencia: Battery-Free Cellphone. Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies. University of Washington. doi>10.1145/3090090
