Electricity Is Produced on Stretching the Carbon Nanotube “Twistron” Yarn

A high-tech “twistron” yarn is developed by a team of scientists that can produce electricity when twisted or stretched. This advancement might result to smart clothes and self-powered wearable health monitors in future. The yarn has several likely applications such as harnessing energy from temperature fluctuations or from the ocean waves’ motion, according to the researchers.

The yarns are fabricated from carbon nanotubes that are void canisters of carbon 10,000x smaller diameter-wise than a human hair. The nanotubes were initially twist-spun by the research team into lightweight, high-strength yarns. So many twists were then introduced to make the yarns extremely elastic that they appeared similar to an over-twisted rubber band.

To facilitate electricity production, the yarns have to be either coated with or submerged in an ionically conducting substance, or electrolyte, that can be as plain as a mixture of usual table water and salt. Co-lead author and a research scientist at UT Dallas, Na Li, said, “These yarns, essentially, are supercapacitors. In a usual capacitor, energy is used—for instance, from battery—to include charges to the capacitors. However, in this case, the yarns are stimulated by the electrolyte itself on inserting the carbon nanotube yarns into an electrolyte bath. No external voltage or battery is required.”

When a harvester yarn is stretched or twisted, the carbon nanotube yarn’s volume reduces, getting the electric charges on it nearer and intensifying their energy, according to Carter Haines from the University of Texas at Dallas, the United States.

This rises the voltage related to the charge accumulated in the yarn, allowing the electricity harvesting. Stretching the winded twistron yarns 30x for a second produced 250 W/kg of peak electrical energy when normalized to the weight of the harvester, said Ray Baughman from the University of Texas at Dallas. The research team explained that a twistron yarn that weighs less than a housefly can power a tiny LED, lighting it up every time they stretched the yarn.

To demonstrate that twistrons can collect waste thermal energy from the surroundings, a twistron yarn was linked by Li to a polymer artificial muscle that expands & contracts when cooled & heated. The mechanical energy produced by the polymer muscle was transformed by the twistron harvester to electrical energy.

Li said, “There is loads of interest to use waste energy for powering the Internet of Things, for instance, the range of distributed sensors. This technology may be utilized for such applications where varying batteries is unfeasible.”

 

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