Researchers have created artificial muscles that can twist 1,000 times more than any suitable material made in the past—a development that could prove useful in robots and prosthetic limbs.

Artificial muscles are typically made from polymers and metals that change size and shape. But to be truly useful, these materials need to twist or rotate when an electric current is applied, and very few such materials created so far can do this.

The new muscles—carbon nanotube fibers spun into a yarn—can produce as much torque, or twisting force, as commercial electric motors.

"This is remarkable," says James Tour, a professor of chemistry and computer science at Rice University, who was not involved with the work. "To have such torsion in a fiber is fascinating and likely to lead to applications in mechanics that have hitherto been unattainable with any other material. [They] really knocked the ball out of the park on this one."