Ever since the invention of cell phones, it seems that they could do more and more while having less and less. Following that logic, researchers from the University of Washington have actually developed a phone that doesn’t need a battery – at all.
This is a major leap forward, and it might completely eliminate the need for cords, chargers, or even dying phones. The way this works is by harvesting only several microwatts of power that it needs in order to operate. And it can get that much simply from light or radio signals.
In fact, the phone has even managed to make a Skype call, and this is still only a prototype. It demonstrated that off-the-shelf components can transmit and receive even speech, as well as communicate with a base station.
More details about this can be found in a paper that was published on July 1. It was published in Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies.
The co-author of the text is Paul G Allen School of Computer Science & Engineering’s associate professor, Shyam Gollakota. In a statement, Gollakota stated that the team has built what is known as the first functioning cell phone that actually consumes no power at all. It only harvests energy from its immediate surroundings, and that this achievement will make everyone rethink how this kind of devices are even designed.
By converting analog signals into digital data, the team was able to eliminate the power-hunger of an average phone. Before they decided to go that way, the phone was simply consuming too much power in order for it to work without a battery. It now takes advantage of vibrations that appear in speakers and microphones within the phone. These happen when a person speaks into it or listens during a phone call.
The phone has an antenna that is connected to these components, and thanks to it, the motion from the vibration is converted into changes in a standard analog radio signal. Basically, your speech patterns are encoded in reflected radio signals, and no power is being consumed.
On the other hand, when it receives speech, it converts the radio signals back into sound vibrations, and then the speaker picks them up. The prototype switches between receiving these signals and transmitting them via a button that replaces these two ‘modes’.
Another member of the team, Joshua Smith, who works as a professor in both UW’s Department of Electrical Engineering and Allen School, has stated that cell phones are devices that we depend on the most. So naturally, if we need a device that can work without a battery, the cellphone is the first choice.
These signals are received and transmitted via a specially designed custom base station that the team made itself. However, they think that this technology might be integrated into regular cellular network infrastructure, or maybe even the WiFi routers.
This is very convenient since pretty much every house has a WiFi router inside, which would guarantee excellent coverage. Of course, the phone still needs small amounts of energy in order to work. The prototype itself needs around 3.5 microwatts for its power budget.
However, this amount of energy is really very small, and it can be harvested via two methods that researchers have demonstrated. One of them is collecting power from radio signals that the base station is transmitting, and the other one is by collecting sunlight through a small solar cell.
There are many similar battery-free technologies that are trying to harvest the power from their environment. The problem is that they usually need to harvest it, convert it, do a task, and then turn off for a minute or two until they repeat the process. Cell phones, on the other hand, need to work continuously, without stopping. Otherwise, a conversation would have to end every time the power runs out.
Dealing with this issue has been the biggest challenge for the team. Still, they managed to deal with it by making cell phones collect between 1 and 10 microwatts from these two sources.
Their next task is to work on the phone’s operating range, as well as conversation encryption. Another goal is to make it possible to stream video via battery-free phone.