Weaving energy-generating fibers into fabrics allows researchers to incorporate autonomous digital wristbands and motion sensors into clothing. This process provides a cheap and scalable method for designing wearable devices, which is Cost-effective solution for making wearable electronics.
“Our process uses embroidery, which is very simple – you can sew our thread directly to the fabric,” said Rong Yin, the author of the study, an assistant professor of textile engineering, chemistry and science at the University of North Carolina said. “When you’re designing clothes, you don’t need to consider wearables. You can attach the power cord after the dress is done.
In a study published in Nano Energy, researchers tested several designs of energy-generating wires. In order to make them durable enough to withstand the tension and twisting of the cutting process, they ended up using five copper wires soldered together, which has a thin polyurethane coating. They then used another material called PTFE to sew them to the cotton fabric.
“It’s a cheap way (Cost-effective solution for making wearable electronics) to create portable electronics using readily available materials,” Yin said. “The electrical characteristics of our model, like other designs, are based on the same energy-generating process.”
The researchers are based on a process that produces electricity called the “triboelectric effect“, which consists of using electrons exchanged by two different materials, such as electricity. They found that the PTFE fabric has the best voltage and current performance when it connects the polyurethane copper wire, compared to other types of fabric they tested, including cotton and silk. They also experimented with coating the plasma sample to increase its sensitivity.
“In our design, you have two layers – one is your polyurethane-coated conductive conductive wires, and the other is PTFE, and they have a space between them,” Yin said. “When the two non-conductor elements combine with each other, one element will lose electrons and some will gain them, and when you combine them, there will be energy.
The researchers tested their threads as motion sensors by wrapping them in denim with PTFE fabric. They put a moving strip on the palms, under the arms, knees and elbows to see the electrical signals that a person’s movements produce. They also put their fabric in the shoe to test its use as a pedometer, finding that their electrical signal varies depending on whether the person walks, runs or jumps. up.
Finally, they tested their yarn in a number key on the hand, which they made by using the number symbols in the fabric and placing them on the PTFE fabric. Depending on the number the person pressed on the keyboard, they saw different electrical signals generated for each number.
“You can put our strap on clothes, and when you move, it creates electrical signals, and these signals can be used as sensors,” Yin said. “When we put embroidery on shoes, if you run, it creates a higher tension than if you walk. When we draw numbers on a grid and press them, it creates a different conflict for each number. It can be used as an interface.
Since the textile products have to be washed, they tested the durability of the woven material in the washing process and research. After they washed their hands and washed the clothes well with soap and dried them in the oven, they did not notice a difference or a slight increase in tension. For the sample of plasma coating, they found that it is weak but still has a high performance compared to the first sample. After the abrasion test, they found that there was no significant change in the electrical output of their designs after 10,000 rub cycles.
In future projects, they plan to integrate their sensors with other devices to add more functionality. “The next step is to integrate these sensors into a wearable system,” Yin said.
The study, “Flexible, Durable, and Washable Triboelectric Yarn and Embroidery for Autonomous Sensing and Human-Computer Interaction,” was published online in Nano Energy.
