This yarn makes its own electricity

Coiled carbon nanotube yarns, created at the University of Texas at Dallas and imaged here with a scanning electron microscope, generate electrical energy when stretched or twisted.
University of Texas at Dallas
In the future, your workout—or your workout gear, to be precise—might generate enough energy to charge your activity tracker. Researchers from the University of Texas at Dallas and South Korea’s Hanyang University (among other institutions) have figured out that by twisting carbon nanotubes into yarn, forming what they call a “twistron harvester,” they can harness mechanical energy and turn it into electricity. They published their results this week in the journal Science.
"The easiest way to think of twistron harvesters is, you have a piece of yarn, you stretch it, and out comes electricity," says lead author Carter Haines, a nanotech researcher at the University of Texas at Dallas.
To be clear, Haines isn’t especially interested in getting your fitness tracker to work longer. He is, however, interested in tapping into the waves of mechanical energy—from ocean waves, to human motions like the vibrations we create when we walk along the sidewalk—and finding a way to use it. We may have learned to harvest the power of the atom, but when it comes to converting mechanical energy to electric, our only economically feasible options are hydropower and wind. The technique detailed in this new study may bring us one step closer to harvesting mechanical energy for a wider variety of uses.
We're not talking about the kind of yarn you knit with. Haines and his co-authors used carbon nanotubes—structures with diameters more than 10,000 times smaller than a human hair. Carbon nanotubes are perhaps most famous as the key ingredient in Vantablack, a super-black "paint" that absorbs 99.965 percent of the visible light that hits it.
The researchers took sheets of carbon nanotubes and spun them in a way reminiscent of the spinning wheel on which Sleeping Beauty pricked her finger. One might say the resultant electrical charge was their own Prince Charming.