While you may be just beginning to reap the benefits of 5G wireless technology, researchers around the world are already hard at work on the future: 6G. One of the most promising breakthroughs in 6G telecommunications is Visible Light Communication (VLC), which is like a wireless version of fiber optics, using flashes of light to transmit information.
Now, a team of researchers from the University of Massachusetts Amherst has announced that they have invented a cheap, innovative way to harvest waste energy from VLCs using the human body as an antenna. This waste energy can be recycled to power a range of wearable devices or even larger electronics.
Jie Xiong, professor of information and computer science at UMass Amherst and lead author of the paper says “VLC is quite simple and interesting, “Instead of using radio signals to send information wirelessly, it uses light from LEDs that can turn on and off up to a million times per second. Part of the appeal of VLC is that the infrastructure is already everywhere our homes, vehicles, streetlights, and offices are lit by LED bulbs that could also transmit data. The receiver can be anything with a camera, such as our smartphones, tablets or laptops”.
Previously, Xiong and first author Minhao Cui, a graduate student in information and computer science at UMass Amherst, showed that there is significant “leakage” of power in VLC systems because the LEDs also emit “side-channel RF signals,” or radio waves. . If this leaked RF energy could be harvested, then it could be used.
The team’s first task was to design a coiled copper wire antenna that would collect the leaked RF, which they did. But how to maximize energy collection?
The team experimented with all sorts of design details, from the thickness of the wire to the number of turns, but they also noticed that the antenna’s efficiency varied depending on what the antenna touched. They tried placing the coil on plastic, cardboard, wood and steel, as well as touching it to walls of various thicknesses, turning phones and laptops on and off. And then Cui got the idea to see what happened when the coil was in contact with the human body.
It immediately became apparent that the human body was the best means of amplifying the coil’s ability to collect leaked RF energy, up to ten times more than the bare coil alone.
After much experimentation, the team came up with the “Bracelet+”, a simple coil of copper wire worn as a bracelet on the upper forearm. While the design can be adapted to be worn as a ring, belt, bracelet or necklace, the bracelet seemed to offer the right balance between energy harvesting and wearability.
“The design is cheap — less than fifty cents,” note the authors, whose paper won the best paper award at the Association for Computing Machinery’s Conference on Embedded Networked Sensor Systems. “But the Bracelet+ can reach up to microwatts, which is enough to support many sensors, such as body-based health monitoring sensors, which require little power to operate due to the low sampling rate and long duration of sleep mode.”
Xiong says “Ultimately we want to be able to harvest waste energy from all kinds of sources to power future technologies”.
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