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How Bizarre

Making artificial muscles with a spin

STRONG SPIRALS  Tightly twisting nylon sewing thread (various diameters shown) forms corkscrews that can work as artificial muscles.

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Scientists have given ordinary fishing line and sewing thread a new twist. When coiled into tight corkscrews, the fibers can lift loads more than 100 times as heavy as those hefted by human muscles.

Each strand of fishing line and nylon thread contains tiny plastic polymers neatly organized into parallel chains. These chains contract when heated, making the strands plump up and shorten. This change forces wound-up fibers to rotate, which can tighten the corkscrew.

Materials scientist Ray Baughman of the University of Texas at Dallas and colleagues harnessed this tightening movement to lift weights. The researchers raised and lowered the weights just by heating or cooling the coiled strands. Supertwisted fibers could one day form soft, strong artificial muscles for robots, which often rely on clunky motors to move. The strands could even be knit into breathable fabrics with weaves that open and close on command, the team reports in the Feb. 21 Science.

THE HEAT IS ON  Heating up an artificial muscle made from coiled fishing line forces the muscle to contract and lift a metal weight. Video courtesy of University of Texas at Dallas

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