The fabric that generates energy from motion

Smart fabrics are increasingly capable of doing some cool things, from analyzing performance levels to dissecting sweat and other bodily fluids.  A recent study from the University of Texas at Dallas documents a new fabric that’s capable of generating energy.

The team developed a prototype fabric that is capable generating electricity whenever it’s stretched or twisted.  The fabric is made from carbon nanotubes, which are around 10,000 times smaller than a human hair.  They are formed into high-strength, lightweight yarns before being coated in electrolyte solutions to give it the electricity generating capability.

“Fundamentally, these yarns are supercapacitors,” the authors say. “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. No external battery, or voltage, is needed.”

The fabric is capable of generating energy because when it’s twisted, the volum of the carbon nanotubes decreases, which allows the electric charges in the yarn to come closer together, and thus increases their energy.  In turn, this then increases the voltage associated with the charge stored in the yarn, which allows electricity to be harvested.

The team managed to stretch each yarn up to 30 times a second, thus generating 250 watts of electricity per kg of fabric.  In a lab environment this allowed them to generate enough power to run a small LED, all with fabric weighing less than the weight of a housefly.

They’re confident that it could be effectively and efficiently woven into clothing and used to harvest energy from our regular daily movement, thus reducing, or even eliminating, the need for batteries for our phones and other electronic devices.

The key to this will be the ability to manufacture the yarn cheaply enough to make it cost effective to introduce to fabrics.  This would also open up other potential use cases, with the team suggesting it could be used to generate energy from ocean wages, for instance.

“If our twistron harvesters could be made less expensively, they might ultimately be able to harvest the enormous amount of energy available from ocean waves,” they say. “However, at present these harvesters are most suitable for powering sensors and sensor communications. 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.”

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