Artificial Muscles

Researchers have discovered a way to spin fishing line and sewing thread into powerful artificial muscles. Even though they are constructed from a single material with a simple design, there is potential for these polymer-based muscles to have a wide range of uses.

“The application opportunities for these polymer muscles are vast,” said study author Ray Baughman, a professor of chemistry at the University of Texas at Dallas, in a press release. “Today’s most advanced humanoid robots, prosthetic limbs, and wearable exoskeletons are limited by motors and hydraulic systems, whose size and weight restrict dexterity, force generation, and work capability.”

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In a paper published Feb. 21 in the journal Science, an international team of researchers led by Baughman and his colleagues describe how they turned high-strength polymer fibers—like those found in fishing lines and sewing threads—into artificial muscles that can lift loads 100 times heavier than human muscles of the same weight and length.

By twisting and coiling the fibers, researchers created small artificial muscles that respond to changes in temperature triggered by various stimuli—electricity, the absorption of light, or chemical reactions. Depending on how the fibers are coiled, the muscles can be set to stretch or contract when heated. This muscle action can be put to use in a range of situations.

“We have woven textiles from the polymer muscles whose pores reversibly open and close with changes in temperature. This offers the future possibility of comfort-adjusting clothing,” said Carter Haines, lead author of the study, in a press release.

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Though the muscles are normally powered by electricity-generated heat, they can also respond to changes in the temperature of the environment. In this way, artificial muscles could close window shutters on a hot day or open them when it cools down, conserving energy without the need for additional electricity to operate them. 

One of the artificial muscles's most important assets is, appropriately, their strength. Working together, one hundred bundles of twisted fishing lines—each bundle only 10 times larger than a human hair—can lift more than half a ton. At the same time, artificial muscles less than the diameter of a human hair could power lifelike facial expressions on robots or respond to touch.

The artificial muscles aren’t ready for the real-world quite yet, but in a few years you might find yourself wearing a shirt that adjusts to the temperature around you, cooling you off or keeping you warm—the ultimate muscle tee.

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