In a joint effort with universities across the globe, researchers at UTD made a breakthrough when they used carbon nanotubes to develop an artificial muscle better than any previously created.

This new artificial muscle works through a process known as torsional actuation; as the muscle twists, it can either expand or contract. The model is capable of twisting more than 1,000 times as much as its predecessors.

The recent discovery makes use of straw-like chains of carbon atoms that have been twisted together to form a more solid strand, known as carbon nanotube yarn. This twisting is similar to how cotton or silk is twisted into a thread.

For the muscle work, the nano-tube yarn is placed in an electrically conductive fluid, known as an electrolyte, and then has a current sent through it.
When this occurs, ions from the surrounding electrolyte rush into the yarn, causing it to expand, said Mikhail Kozlov, UTD research scientist. It is this expansion that causes the yarn to spin, similar to the unraveling of a spring.

The yarn can spin at speeds of nearly 600 rotations per minute in either a clockwise or counter- clockwise direction, depending on the voltage passed through it, and is even thinner than a strand of hair.

In the experiments conducted with the yarn, it was affixed with a plastic paddle to help the researchers visualize the spinning of the yarn. This paddle was 1,800 times as heavy as the nanotube yarn, proving the strength of this invention. By nature, carbon nanotubes are more than 100 times stronger than steel.
Other UTD research personnel, Ji-Young Oh, and Shaoli Fang, worked with Kozlov on the project.

Ray Baughman, director of the UTD Nano-Tech Institute, served as the corresponding author. Other universities involved in this particular discovery include the University of Wollongong in Australia, the University of British Colombia in Canada and Hanyang University in South Korea.

“Many people are looking for a material that can act like a natural muscle and deliver performance comparable to a natural muscle,” Kozlov said. “Our goal is to develop this material. We all know it is possible; we all have muscles, after all. But such a material is hard to make artificially.”