A Buff New Twist on Carbon Nanotube Artificial Muscles

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Scientific American

For years artificial muscles have promised to deliver a more flexible, more durable alternative to electric motors and hydraulic systems. These lab-made actuators are usually created by putting an electrical charge into a piece of polymer or into an aerogel sheet made from carbon nanotubes, causing those materials to expand and contract. This motion could someday be used to power turbines, animate robots or move prosthetic limbs.
In a new study published in the October 14 issue of Science, an international team of researchers describes how they’re taking carbon nanotube artificial muscles in a new direction. Scientists at the University of Texas at Dallas’ Alan G. MacDiarmid NanoTech Institute have already demonstrated in the lab the ability of these muscle-like carbon nanotubes to flex even in extreme temperatures that would freeze or, on the other end of the spectrum, decompose electroactive polymer-based artificial muscles.
Their latest work—with scientists from the University of Wollongong in Australia, the University of British Columbia in Canada, and Hanyang University in Korea—indicates that these carbon nanotubes can be spun into yarns (see inset to the left) and, when dipped into an electrolyte solution, move in a twisting direction that mimics the stiffness, extension, bending and torsion of natural muscles found in an elephant’s trunk and squid tentacles. The researchers found that the yarns can even untwist (moving with the opposite rotation) when the applied voltage is changed.
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