Researchers from North Carolina State University discovered a solution to prevent electrical faults in yarns that store electrical energy in a recent study. The results may eventually aid in creating “smart fabrics” that gather energy from the wearer’s movements and incorporate power sensors and wearable electronics.
The researchers revealed in npj Flexible Electronics that by wrapping yarns with an insulating thread, they could prevent short-circuiting in supercapacitors, which are electrical devices that store energy.
They also examined the yarns’ strength and durability to ensure that they would continue to function after going through the knitting and weaving operations.
“A supercapacitor functions like a battery, but in this case, we’re working on a flexible battery shaped as a textile yarn that you could weave or knit into your T-shirt or sweater,” said Wei Gao, associate professor of textile engineering, chemistry and science, and a University Faculty Scholar at NC State.
“In this study, we have woven this yarn into a piece of fabric so that it can store electrical energy, and eventually we want to use it to power whatever electronic devices you need, whether it be a sensor, a light, or even a cell phone.”
While research into “yarn-shaped supercapacitors” is promising, researchers say there is a continuous problem with their design: yarn-shaped supercapacitors are more prone to short circuit as their length rises.
When an electric current flows in an unanticipated channel, it is called short-circuiting. A short circuit might generate a burst of heat energy or perhaps a fire, which is a safety hazard.
The yarns need to be flexible and strong enough so that when you bend, stretch and press them, they keep their original electrical performance after all of those mechanical deformations. The yarns all kept their original performance, even after going through weaving and knitting.
Nanfei He
“Everybody is trying to make smart electronics that can be incorporated into cloth or fabric,” Gao said. “What we found is if you try to make a supercapacitor yarn longer than 8 inches, it’s pretty easy for this device to short-circuit. It’s pretty dangerous, and it’s something nobody wants to encounter when wearing a smart suit.”
To address this issue, the researchers investigated what would happen if the super-capacitor yarn electrodes were wrapped in insulating threads. The threads were supposed to operate as a physical barrier, preventing short-circuiting by preventing the opposing electrodes from contacting each other.
By attaching the electrodes to a power supply and recording the device’s current response, they were able to assess its performance. They also put the yarns to the test to see how well they could hold a charge. After charging and discharging the yarns 10,000 times, they discovered that they retained 90% of their initial energy.
By weaving their yarn-shaped supercapacitors into a fabric, the researchers were able to assess if they could endure bending and stretching.
“The yarns need to be flexible and strong enough so that when you bend, stretch and press them, they keep their original electrical performance after all of those mechanical deformations,” said the study’s lead author Nanfei He, postdoctoral research scholar in textile engineering, chemistry and science at NC State.
“The yarns all kept their original performance, even after going through weaving and knitting.”
The yarn-shaped supercapacitor was created using traditional textile production procedures, according to the researchers.
“All of these processes can be scaled up very easily,” He said.
The researchers plan to make their idea into clothing and try to integrate it with additional energy-generating devices in the future.
“Materials innovation and process engineering are critical to the scalability and device performance,” said Feng Zhao, CEO of Storagenergy Technologies Inc., the industrial partner of the project. “We have developed a process to produce thousands of meters of high-performance yarns in a continuous manner.”
The research was published in the journal npj Flexible Electronics under the title “Separator Threads in Yarn-Shaped Super-capacitors.” Storagenergy Technologies Inc.’s Junhua Song, Jinyun Liao, and Feng Zhao were the other writers, in addition to He and Gao.
The study was supported by Storagenergy Technologies Inc., and funded by the United States Army under contract numbers W911NF19C0074 and W911NF18C0086.
