High-tech yarns generate electricity from twisting and stretching

An international team of researchers led by researchers at the University of Texas (UT) at Dallas has devised a way to harvest electricity from carbon nanotube yarns, as they stretch and twist.

The development follows a decade and more of efforts to develop the yarns.

The research which is described in the journal Science, shows promise for immediate use in powering small sensor nodes in Internet of Things (IoT) applications, according to commentators.

According to the team, its nanotube yarns could produce larger amounts of energy by flexing and twisting in response to the movement of ocean waves.

According to commentators, though these nanotube yarns were exploiting a piezoelectric effect, in which a material can generate an electric charge in response to applied mechanical stress, the yarn's behaviour made it more closely tied to so-called electroactive polymers (EAPs), which are a kind of artificial muscle.

''Basically what's happening is when we stretch the yarn, we're getting a change in capacitance of the yarn. It's that change that allows us to get energy out,'' explains Carter Haines, associate research professor at UT Dallas and co-lead author of the paper describing the research, in an interview with IEEE Spectrum.

In the study, the researchers reported stretching their yarns, called twistron, 30 times a second, and generating 250 watts per kg of peak electrical power, about 100 times higher than that of other wearable fibers.

Meanwhile, Xinhua reported that the researchers showed in the lab, that a twistron yarn weighing less than a housefly could power a small LED, which lit up each time the yarn was stretched.

"Just stretch it and out comes electricity directly," says co-lead author Na Li, a research scientist in the Alan G MacDiarmid NanoTech Institute at the University of Texas at Dallas, IANS reported.

According to Li, the yarns were constructed from carbon nanotubes, hollow cylinders of carbon 10,000 times smaller in diameter than a human hair.