by New high-tech yarn harvests mechanical energy
A team of researchers from the University of Texas at Dallas have invented nanotube yarns that convert mechanical motion into electricity when stretched or twisted. As first described in a 2017 study published in the journal Science, the yarns are made of carbon nanotubes, hollow cylinders of carbon 10,000 times smaller in diameter than a human hair. A study published on Jan. 26 energy of nature reported that these earlier versions of yarn dubbed whirl were highly elastic and could generate electricity by repeatedly stretching and relaxing or twisting and untwisting.
Since then, the team has refined the whirl process, resulting in fibers that are more efficient and produce more power than the older models. In their new study, the researchers didn’t twist the fibers enough to cause them to coil up. Instead, they interlaced three individual strands of spun fibers into a single yarn, constructed in a manner similar to traditional wool or cotton yarn, but with a different twist.
dr Ray Baughman, director of the Alan G. MacDiarmid NanoTech Institute at UT Dallas and corresponding author of the study, states: “Pleated yarns used in textiles are typically made from individual strands that are twisted in one direction and then plied together in the opposite direction to create the final yarn. This heterochiral construction provides stability against untwisting.. Baughman, the Robert A. Welch Distinguished Chair in Chemistry at the School of Natural Sciences and Mathematics, adds: “In contrast, our highest-performing carbon nanotube twistrons have the same handedness of rotation and position—they are homochiral rather than heterochiral,” said 
all images from the University of Texas at Dallas
new yarns for sensing and harvesting human motion
the researcher were able to show through experiments that the new yarns showed an energy conversion efficiency of 17.4% for energy generation by tension (elongation) and 22.4% for energy generation by torsion (twisting). This achieved a peak energy conversion efficiency of 7.6%. “These twistrons have higher output power per harvester weight over a wide range of frequencies – between 2 Hertz and 120 Hertz – than previously reported for any material-based mechanical energy harvester without a twistron.” said Baughman.
Baughman mentioned that the team was able to improve Pled’s performance whirl by introducing lateral compression of the yarn when stretched or twisted. This updated process allows the plies to come into contact with each other in a way that affects the electrical properties of the yarn.
‘Our materials do something very unusual’ explained Baughman. “As you stretch them, they don’t become less dense, they become denser. This densification pushes the carbon nanotubes closer together, contributing to their energy-harvesting ability. We have a large team of theorists and experimenters trying to understand more fully why we are getting such good results.’
Researchers discovered that forming the yarn from three layers yielded optimal performance. After several tests, they found that the new yarns could be used to capture and harvest human movement. To demonstrate the practicality, the team sewed the CNT yarns into a cotton fabric patch, which was then wrapped around a person’s elbow. Electrical signals were generated as the subject repeatedly flexed their elbow.
the nanotubes are hollow carbon cylinders with a diameter 10,000 times smaller than a human hair
Project info:
Surname: new carbon nanotube yarn
Researcher: The University of Texas at Dallas | @ut_dallas
Christina Petridou I design boom
February 01, 2023
