New Wearable Device Can Power Electronics While You Sleep

(CN) — Engineers at the University of California San Diego have developed a small fingertip device that can generate power from human sweat regardless of the wearer’s activity level.

The tiny device is a thin flexible strip that is worn over a fingertip and can generate small amounts of electricity when the wearer sweats or presses on it. The device resembles a finger bandage and is a breakthrough in the field of wearable technology.

"Unlike other sweat-powered wearables, this one requires no exercise, no physical input from the wearer in order to be useful. This work is a step forward to making wearables more practical, convenient and accessible for the everyday person," said Lu Yin, a nanoengineering Ph.D. student at the UC San Diego Jacobs School of Engineering and co-author of a research paper published Tuesday in the journal Joule.

The fingers may seem like an odd choice, but fingertips are surprisingly sweaty – most people just don't notice.

"The reason we feel sweatier on other parts of the body is because those spots are not well ventilated," Yin said in a statement. "By contrast, the fingertips are always exposed to air, so the sweat evaporates as it comes out. So rather than letting it evaporate, we use our device to collect this sweat, and it can generate a significant amount of energy."

Despite the seeming advantages, the fingertips require special materials to make the device work. The researchers had to make parts of the wearable very absorbent and efficient at converting the useful chemicals in human sweat into electricity.

Specifically, the device uses a padding of carbon foam electrodes equipped with enzymes that cause chemical reactions between lactate and oxygen molecules found in sweat to generate electricity. 

Beneath the electrodes is a chip made of a so-called piezoelectric material that generates electrical energy when pressed. The term refers to materials that generate an electrical charge in reaction to pressure or latent heat.

Researchers tested the device by having an individual wear the device while doing low energy activities. They found that from 10 hours of sleep, the device collected enough energy to power an electronic wristwatch for 24 hours. The device also collected energy from the wearer when they did everyday tasks like typing on a computer.

"We envision that this can be used in any daily activity involving touch, things that a person would normally do anyway while at work, at home, while watching TV or eating," said Joseph Wang, a professor of nanoengineering at the UC San Diego Jacobs School of Engineering and the study's senior author. "The goal is that this wearable will naturally work for you and you don't even have to think about it."

During their experiments, the researchers had a wearer connected to a chemical sensor and low-power display and found that the wearer pressing the fingertip device every second or simply just wearing it for two minutes, was enough to power both the sensor and display.

In another experiment, a subject took a vitamin C pill and used the finger-powered device to power a sensor to read their own vitamin C level.

"Our goal is to make this a practical device," Yin said. "We want to show that this is not just another cool thing that can generate a small amount of energy and then that's it – we can actually use the energy to power useful electronics such as sensors and displays."

To reach that goal, the researchers plan to work on making the device more durable and efficient, and in future studies will combine their device with other energy collection technologies.

Yin and Wang were joined on the project by UC San Diego nanoengineering Ph.D. students Jong-Min Moon and Juliane Sempionatto, who also co-authored the paper.

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