Artificial muscle consisting of yarns spun from carbon nanotubes and soaked in paraffin wax can lift 200 times the weight that natural muscles the same size can carry.

Credit: SCIENCE/AAAS

The 'muscle' (pictured), designed by Ray Baughman of the University of Texas at Dallas and his colleagues, produces torque by twisting and untwisting. Heating the yarn's wax component with a flash of light or by passing an electric current through the yarn causes it to expand, twist and shorten. The muscle rapidly contracted and relaxed over more than one million cycles.

The authors used a 100-micrometre-wide yarn to power a miniature catapult and launch a piece of foil, demonstrating a torque slightly higher than that of large electric motors. The muscles could be used as sensors and actuators in a variety of systems, the authors say.

Science 338, 928–932 (2012)