In a groundbreaking endeavor to create versatile wearable electronic devices, researchers from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland have developed new scalable approaches for battery- and solar-powered fibers. These advanced fibers can be woven into clothing, enabling the potential to harvest and store electrical energy, according to a statement by the scientists.

Traditional fiber batteries often face challenges with scalability and performance limitations. To overcome these hurdles, the APL team engineered fiber batteries using a stacked design similar to conventional pouch cells. This innovative method involves layer lamination and laser machining, producing battery fibers as narrow as 650–700 µm. These fibers could power high-performance wearable electronics that retain the qualities of conventional textiles, such as breathability, stretchability, and washability, as reported by Tech Xplore.

“As demands for electronic textiles change, there is a need for smaller power sources that are reusable, durable, and stretchable,” stated Konstantinos Gerasopoulos, assistant program manager for physics, electronic materials, and devices at APL and the lead investigator of this project. “Our vision is to develop solar harvesting fibers that can convert sunlight to electricity and battery fibers that can store the generated electricity in the textile.”

The progress hinges on developing poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) separators. These separators enable the lamination of conventional battery electrodes using a heated rolling press. The laminated strips are then laser-cut to form fibers, which have shown energy densities capable of storing up to 0.61 milliwatt-hours of energy per centimeter of fiber length.

The fiber batteries have been designed for roll-to-roll processing, marking a significant departure from previous methods. This new approach ensures optimal utilization of active materials, minimal use of inactive materials, scalability, and compatibility with widely used battery industry equipment. “We were always designing with roll-to-roll compatibility in mind,” noted Rachel Altmaier, the study’s lead author. “We need to be able to run all of our processes continuously or else what we develop isn’t relevant. This process could be dropped into an existing manufacturing line.”

The custom-made battery equipment converts the laminated flat strips of anode and cathode electrodes with a polymer separator into a stack, which is then laser-cut into thin fibers. “We can process 100 meters of total fiber in a little over five hours,” articulated Jason Tiffany, an engineer at APL and co-author of the paper. “With our process, we can make the fibers smaller and more energy-dense, which could open even more opportunities for textile applications.”

The solar-powered fibers were adapted from conventional solar cell technology by assembling them onto flexible circuit boards and encapsulating them in polymer for integration into textiles. Despite extensive bending and exposure to light, these fibers maintained high performance and durability. “The biggest challenge with current solar cell technology is its rigidity,” emphasized Michael Jin, lead author of the solar cell paper. “You can imagine shrinking solar panels, like those on a rooftop, into a tiny solar fiber is very challenging.”

“We used standard microelectronics fabrication processes to develop a novel approach that has transformed current rigid solar cell technology into flexible and durable fibers,” Jin added. “Even after bending the fiber 8,000 times, we saw no change in its performance.”

This pioneering technology could enable various applications, such as health monitoring, warming clothing, and providing power for soldiers’ equipment. The study represents a paradigm shift in fiber battery technology, paving the way for high-performance wearable and textile electronics.

“Textiles that integrate light energy harvesting and battery fibers could revolutionize what wearables today can achieve. Very soon, these fibers will enable distributed fabric-based power, heating, communications, and sensing while providing the comfort and ease of regular textiles,” stated Jeff Maranchi, research program area manager in APL’s Research and Exploratory Development Department.

This innovative development in fiber technology heralds a new era in wearable electronics, bringing futuristic applications closer to reality.

By Impact Lab