Textiles with a twist
Nano-yarns could soon revolutionise wearable technology.
It’s a rite of passage in high-school physics to twist a length of string and then let it go to demonstrate how potential energy converts to kinetic energy.
Perhaps Carter Haines of the University of Texas, Dallas, was particularly impressed by this evergreen lesson. It would happily explain the inspiration for an invention he and colleagues describe in the journal Science.
Haines’ team has created a new type of yarn from carbon nanotubes, which generates electricity when stretched or twisted. These “twistrons”, the scientists suggest, have a wide range of potential uses, including harvesting power from ocean waves, or functioning as a wearable heart monitor.
To create the basic structure, Haines and colleagues compiled nanotubes – tiny cylinders 10,000 times smaller than the width of a human hair – and twisted them together, like a strand of wool.
Before that, however, the yarns were coated with a conductive substance – an electrolyte. High tech met low: salt water was all that was needed for proof of concept.
The tighter the yarns were twisted, the closer together the electric charges embedded in them became, increasing their energy output.
“Fundamentally, these yarns are supercapacitors,” says co-author Na Li. “When you insert the carbon nanotube yarn into an electrolyte bath, the yarns are charged by the electrolyte itself. No external battery, or voltage, is needed.”
For such a simple machine, the electrical output is impressive. The scientists calculated that stretching them 30 times a second produced about 240 watts of power per kilogram of yarn.
Haines and his colleagues have already filed a patent on twistrons, and see them as a possible solution to one of the major hurdles facing manufacturers of “smart” clothing and other wearables. “Electronic textiles are of major commercial interest,” team member Ray Baughman notes, “but how are you going to power them?”
CREDIT: UNIVERSITY OF TEXAS AT DALLAS Smart-dressed: twisted carbon nanotubes might one day power your shirt.
SACHSEN-ANHALT, JURAJ LIPTÁK CREDIT: LANDESAMT FÜR DENKMALPFLEGE UND ARCHÄOLOGIE Tar produced without ceramics, using only Neanderthal technology.