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Human Body as an Antenna to Harvest Waste Energy From VLC

While people may be only beginning to benefit from the advantages of 5G wireless technology, scientists all over the world are already focusing their efforts on the next generation: 6G.

The team experimented using different daily objects to amplify the harvested power, and discovered that the human body is one of the best materials. Image Credit: Cui, et al.

Visible Light Communication (VLC), a wireless version of fiberoptics that uses flashes of light to convey information, is one of the most promising advancements in 6G telecommunications.

A group of scientists from the University of Massachusetts Amherst has reported the development of a low-cost, unique method for harvesting waste energy from VLC by utilizing the human body as an antenna. This waste energy can be recycled and used to power a variety of wearable gadgets or even larger electronics.

VLC is quite simple and interesting. 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.

Jie Xiong, Study Senior Author and Professor, Information and Computer Sciences, University of Massachusetts Amherst

One of the appealing aspects of VLC is that the infrastructure is already in place—LED bulbs that illuminate homes, vehicles, streetlights, and offices could all be carrying data.

Xiong adds, “Anything with a camera, like our smartphones, tablets or laptops, could be the receiver.”

Earlier, Xiong and first author Minhao Cui, a Graduate student in information and computer sciences at UMass Amherst, demonstrated that there is considerable “energy leakage” in VLC systems due to the LEDs emitting “side-channel RF signals,” or radio waves. If the leaked RF energy could be recovered, it could be used.

The initial goal for the group was to create an antenna out of coiled copper wire to gather the leaked RF, which they accomplished. But how can we maximize energy collection?

The researchers experimented with various design elements, such as wire thickness and the number of times it was coiled, but they also discovered that the efficacy of the antenna changed depending on what the antenna touched.

Investigators attempted resting the coil on plastic, cardboard, wood, and steel, as well as contacting it to varying thicknesses of walls, phones that were turned on and off, and laptops. Cui then had the smart idea to investigate what happened when the coil came into contact with a human body.

It was immediately obvious that a human body is the best medium for enhancing the coil's ability to capture leaked RF energy, up to ten times more than the bare coil alone.

After much experimentation, the team 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. 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,” added the authors, whose research grabbed the prestigious Best Paper Award from the Association for Computing Machinery’s Conference on Embedded Networked Sensor Systems.

Ultimately, we want to be able to harvest waste energy from all sorts of sources in order to power future technology.

Jie Xiong, Study Senior Author and Professor, Information and Computer Sciences, University of Massachusetts Amherst


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