Researchers have developed yarn made out of nanotubes that can generate electricity and have the potential to, one day, replace batteries.
This week, a team of scientists led by The University of Texas at Dallas and Hanyang University in South Korea revealed the research project. It was published in the journal Science.
The team describes the high-tech material as "twistron" yarn, which, when stretched or pulled, produces electricity. The material is based on carbon nanotubes, hollow cylinders of carbon 10,000 times smaller than a human hair. Its is twisted and spun with enough tension to make them appear as an "over-twisted" rubber band, according to the team.
In order to produce electricity, the yarn must be submerged or coated with a conductive material or electrolyte.
However, the chemical components needed do not have to be complex or difficult to acquire -- instead, they can be as simple as table salt and water.
"Fundamentally, these yarns are supercapacitors," said Dr. Na Li, a research scientist at the NanoTech Institute and co-lead author of the study. "In a normal capacitor, you use energy -- like from a battery -- to add charges to the capacitor."
"But in our case, when you insert the carbon nanotube yarn into an electrolyte bath, the yarns are charged by the electrolyte itself," Li added. "No external battery, or voltage, is needed."
During tests, the scientists found that when the yarn was twisted or stretched, the tension decreased the volume of the carbon nanotubes embedded within, bringing the electrical charges closer together and increasing energy rates. In turn, this increased the voltage of the charge stored in the material, allowing the nanotubes to harvest electricity.
According to one of the authors of the study, Dr. Ray Baughman, stretching the twistron yarn 30 times a second generates 250 watts per kilogram of power.
However, the output does rely on how much yarn is used. A piece of the yarn, which weighs less than a housefly, can power a small LED light, for example, whereas a larger portion of the electronic textile could be used for major energy-harvesting operations.
"Harvesting electrical energy from human motion is one strategy for eliminating the need for batteries," Baughman said. "Our yarns produced over a hundred times higher electrical power per weight when stretched compared to other weaveable fibers reported in the literature."
The research team said the nanotube yarn has a variety of potential applications, including harvesting energy from ocean waves, powering small LED lighting systems, acting as self-powered breathing monitors when sewn into clothing, harvesting thermal energy from the environment, or, perhaps of most interest, as a way to limit power leakage and inefficiency in Internet of Things (IoT) devices.
"At present, these harvesters are most suitable for powering sensors and sensor communications.," Baughman said. "However, based on demonstrated average power output, just 31 milligrams of carbon nanotube yarn harvester could provide the electrical energy needed to transmit a 2-kilobyte packet of data over a 100-meter radius every 10 seconds for the Internet of Things."
The results of the study are impressive and a patent has been filed. However, the next challenge the scientists face is how to make the nanotube yarn cheap enough to be financially viable for commercial applications.
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