Energy-Harvesting Yarns Generate Electricity
TEHRAN (Tasnim) - Scientists developed high-tech yarns that generate electricity when they are stretched or twisted. 'Twistron' yarns have many possible applications, such as harvesting energy from the motion of ocean waves or from temperature fluctuations.
The study, carried out by an international research team led by scientists at The University of Texas at Dallas and Hanyang University in South Korea, was published in the August 25 issue of the journal Science.
When sewn into a shirt, these yarns served as a self-powered breathing monitor.
"The easiest way to think of twistron harvesters is, you have a piece of yarn, you stretch it, and out comes electricity," said Dr. Carter Haines, associate research professor in the Alan G. MacDiarmid NanoTech Institute at UT Dallas.
The yarns are constructed from carbon nanotubes, which are hollow cylinders of carbon 10,000 times smaller in diameter than a human hair. The researchers first twist-spun the nanotubes into high-strength, lightweight yarns. To make the yarns highly elastic, they introduced so much twist that the yarns coiled like an over-twisted rubber band.
In order to generate electricity, the yarns must be either submerged in or coated with an ionically conducting material, or electrolyte, which can be as simple as a mixture of ordinary table salt and water.
When a harvester yarn is twisted or stretched, the volume of the carbon nanotube yarn decreases, bringing the electric charges on the yarn closer together and increasing their energy, Haines said. This increases the voltage associated with the charge stored in the yarn, enabling the harvesting of electricity.