Ultra-Strong Artificial Muscles Made From Carbon Nanotubes

UT Dallas researchers have made artificial muscles from carbon nanotube yarns that have been infiltrated with paraffin wax and twisted until coils form along their length. The diameter of this coiled yarn is about twice the width of a human hair. Credit: UT Dallas

In order to showcase ultra-strong artificial muscles, Ray Baughman from the University of Texas at Dallas and his colleagues built a catapult.

The scientists published their findings in the journal Science. The device contains yarns similar in diameter to human hair, spun from carbon nanotubes and soaked in paraffin wax. When a current is passed through the yarn, the wax heats up and expands. As the yarn swells, its particular helical weave causes it to shorten, and the muscle contracts. As it cools, the yarn relaxes and returns to its original length. When coiled lightly or heated to high enough temperatures, wax-free yarns behave in the same fashion.

The torque produced by the twisting and untwisting of the yarns is sufficient to power a miniature catapult. The yarn can haul 200 times the weight that a natural muscle of the same size can, and generates more torque than a large electric motor if compared by weight. Currently, the available manufacturing techniques have limited the weight of the yarn. They can make yarn that lifts up 50 grams. That doesn’t sound like much, but researchers have shown the nanotube yarns lifting loads as much as 50,000 times greater than their own weight.

The yarn could be used as actuators in microfluidic systems or as components in optical cameras, within 2 years. They could also be used as intelligent sensors.

Video courtesy of The Alan G. MacDiarmid NanoTech Institute, The University of Texas at Dallas.

Reference: “Electrically, Chemically, and Photonically Powered Torsional and Tensile Actuation of Hybrid Carbon Nanotube Yarn Muscles” by Márcio D. Lima, Na Li, Mônica Jung de Andrade, Shaoli Fang, Jiyoung Oh, Geoffrey M. Spinks, Mikhail E. Kozlov, Carter S. Haines, Dongseok Suh, Javad Foroughi, Seon Jeong Kim, Yongsheng Chen, Taylor Ware, Min Kyoon Shin, Leonardo D. Machado, Alexandre F. Fonseca, John D. W. Madden, Walter E. Voit, Douglas S. Galvão and Ray H. Baughman,
16 November 2012, Science.
DOI: 10.1126/science.1226762