A New Twist on Artificial ...

A New Twist on Artificial Muscles

Carbon nanotube yarns produce as much torque as an electric motor.

Thin fiber: A scanning electron microscope shows a 3.8-micrometer-diameter carbon nanotube yarn that twists when connected to an electrode and immersed in conductive liquid.
University of Texas at Dallas

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."

The twisty nanotube yarn could open up novel uses. It might help miniaturize electric motors, compressors, and turbines. Tiny pumps based on the rotating actuator could be integrated into lab-on-a-chip devices, which currently use large external pumps. "This is a fascinating new way to provide torsion," says Ray Baughman, director of the Nanotech Institute at the University of Texas at Dallas. Baughman led the work.

In a paper published on the website of the journal Science today, the researchers show that the new yarn can spin a paddle 1,800 times heavier than itself at 590 revolutions per minute. They demonstrated how a simple device based on this concept could be used to mix two liquids on a microfluidics chip; in a fluid mixer, a 15-micrometer-wide yarn rotated a paddle that was 200 times wider and 80 times heavier than itself at up to one rotation per second.

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