The team developed a coil with different designs to harvest RF leakage. (Image Credit: Cui et al., 10.1145/3560905.3568526)
Many people have started using 5G technology, but worldwide researchers are currently developing 6G telecommunications. Visible Light Communications (VLC), technology that uses light flashes to transmit data, could emerge as a promising 6G breakthrough. The University of Massachusetts Amherst researchers recently developed a low-cost VLC waste energy harvesting technique that involves using the human body as an antenna. The waste energy can then be recycled to power wearable devices and potentially larger electronics.
“VLC is quite simple and interesting,” says Jie Xiong, professor of information and computer sciences at UMass Amherst and the paper’s senior author. “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.” VLC is very appealing because it’s already in everyday applications, including vehicles, homes, offices, and streetlights. “Anything with a camera, like our smartphones, tablets or laptops, could be the receiver,” says Xiong.
Xion and Minhao Cui, a UMass Amherst graduate student in information and computer science, previously demonstrated that VLC systems have significant energy leakage due to the LEDs emitting side-channel RF signals. This RF energy could then be harvested and used for various applications.
First, the team designed an antenna made of coiled copper wire that collects the leaked RF. They also implemented different design details, from the wire’s thickness to how often it was coiled. The antenna’s efficiency varied based on what it touched. Placing the coil on cardboard, wood, plastic, and steel and touching it on walls with different thicknesses caused it to turn phones and laptops on/off.
Placing the coil on different surfaces powered the phone, laptop, and tablet on/off. (Image Credit: Cui et al., 10.1145/3560905.3568526)
Cui then wondered what would happen if the antenna came in contact with a human body. They discovered that a human body amplifies the coil’s capability to harvest RF energy leakage by ten times more than the bare coil. The team also created Bracelet+, a coil of copper wire worn on the upper forearm like a bracelet. Researchers can change the design so it can be worn as a belt, anklet, ring, or necklace.
“The design is cheap—less than fifty cents,” note the authors, whose paper won the prestigious Best Paper Award from the Association for Computing Machinery’s Conference on Embedded Networked Sensor Systems. “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.”
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