Researchers continue to search for new, lightweight, and renewable ways to power wearable devices and sensor-filled clothing for tracking health, fitness, and providing other types of data.
A research team in Japan has invented a good candidate for one with an ultra-thin photovoltaic device that is both stretchable and waterproof, making it well-suited to repeated washing and wear. This makes it potentially a good fit to provide renewable power for devices such as health monitors and other sensors integrated with clothing.
The scientists from RIKEN Center for Emergent Matter Science and the University of Tokyo coated the device on both sides with stretchable and waterproof films, which can continue to provide electricity from sunlight even after becoming wet and being stretched and compressed.
“For potential applications of textile-compatible power sources, they need to withstand several washing processes,” said Kenjiro Fukuda, a RIKEN researcher and co-author of a paper on the work published in the journal Nature Energy. “[This use] requires waterproof and stretchable solar cells.”
An ultra-thin photovoltaic device invented by scientists from RIKEN Center for Emergent Matter Science and the University of Tokyo that is both stretchable and waterproof, making it well-suited to repeated washing and wear. Researchers said it a good fit to provide renewable power for devices such as health monitors and other sensors integrated with clothing. (Source: RIKEN)
For their work, researchers used thin and flexible organic photovoltaic cells based on a material called PNTz4T, which they had developed in earlier research. They deposited the device in an inverse architecture—also previously developed—onto a 1-um-thick parylene film.
Then the team added what Fukuda said is the “uniqueness” of their work—placing the device onto acrylic-based elastomer and coating the top side of the device with an identical elastomer, giving it a coating on both sides to prevent water infiltration.
“The idea is to coat ultra-thin--3-micron-thick--on both sides with elastomers that simultaneously realize stretchability and stability in water while maintaining a high efficiency [of] 7.9% for maximum value,” he told Design News. “We believe that the ultra-thin organic solar cells coated with elastomer sheets should be envisaged for practical wearable applications to add stretchability to the devices and protect them from both environmental and mechanical damage caused by scratching, shearing, and squeezing.”
The elastomer allows both light to enter while preventing water and air from leaking into the cells, making them more long-lasting than in previous experiments by the team, Fukuda said. In experiments, researchers generated up to 15 megaWatts using solar cells on 5 cm-by-5 cm films. Increasing the film size enables higher power, he added.
Researchers plan to continue their work to address two key areas of criticism for their current invention—to achieve higher energy-conversion efficiency as well as improved air stability, Fukada said.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years.