Harvesting waste energy from VLC using the human body
Researchers at the University of Massachusetts Amherst have announced that they have invented a low-cost, innovative way to harvest the waste energy from visible light communication (VLC) – seen as a technology that supports 6G because of its huge bandwidth and terahertz operating frequencies – by using the human body as an antenna. This waste energy, say the researchers, can be recycled to power an array of wearable devices, or even, perhaps, larger electronics.
“VLC is quite simple and interesting,” says Jie Xiong, professor of information and computer sciences at UMass Amherst and the senior author of a paper on the research. “Instead of using radio signals to send information wirelessly, it uses the light from LEDs that can turn on and off, up to one million times per second.”
Part of the appeal of VLC is that the infrastructure is already everywhere — homes, vehicles, streetlights and offices are all lit by LED bulbs, which could also be transmitting data.
“Anything with a camera, like our smartphones, tablets or laptops, could be the receiver,” says Xiong.
In creating the approach, the researchers first designed an antenna out of coiled copper wire to collect the leaked RF. To maximize the collection of energy, the researchers experimented with all sorts of design details, from the thickness of the wire to the number of times it was coiled, but they also noticed that the efficiency of the antenna varied according to what the antenna touched.
They tried resting the coil on plastic, cardboard, wood and steel, as well as touching it to walls of different thicknesses, phones powered on and off and laptops. And then they decided to see what happened when the coil was in contact with a human body.
Immediately, say the researchers, it became apparent that a human body is the best medium for amplifying the coil’s ability to collect leaked RF energy, up to ten times more than the bare coil alone. After much experimentation, the researchers came up with “Bracelet+,” a simple coil of copper wire worn as a bracelet on the upper forearm.
While the design can be adapted for wearing as a ring, belt, anklet or necklace, the bracelet seemed to offer the right balance of power harvesting and wearability.
“The design is cheap — less than fifty cents,” say the researchers. “But Bracelet+ can reach up to micro-watts, enough to support many sensors such as on-body health monitoring sensors that require little power to work owing to their low sampling frequency and long sleep-mode duration.”
“Ultimately,” says Xiong, “we want to be able to harvest waste energy from all sorts of sources in order to power future technology.”
For more, see “Bracelet+: Harvesting the Leaked RF Energy in VLC with Wearable Bracelet Antenna.”