PerspectiveMaterials Science

Speeding Up Artificial Muscles

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Science  16 Nov 2012:
Vol. 338, Issue 6109, pp. 893-894
DOI: 10.1126/science.1230428

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Artificial muscles—materials that change size or shape when activated by some stimulus—are attractive for applications in robotics and in sensing and control technologies because they provide large force and motion while being compact and lightweight. Currently, artificial muscles (and smart materials in general) are limited in the combinations of force, motion, and speed that they can generate. Also, their efficiency may be low, or they may need to operate in a certain environment, such as within an electrolyte. On page 928 of this issue, Lima et al. (1) describe a faster and longer-stroke artificial muscle based on yarns made from sheets of carbon nanotubes in which liquid electrolytes are replaced with a solid guest or filler material such as wax; melting and solidifying the wax twists or untwists the yarn and generates motion. Other guest materials are activated by chemical absorption or illumination by light. The new artificial muscle outperforms existing artificial muscles (2), allowing possible applications such as linear and rotary motors, and might replace biological muscle tissue if biocompatibility can be established.