An artificial limb is driven by two fiber-based muscles Mehmet Kanik and Sirma Orguc, Massachusetts Institute of Technology

Three teams have developed artificial muscles that can lift 1000 times their own weight. They hope the new fibres could be used in prosthetic limbs, robots, exoskeletons, and even in clothing.

All three teams have developed their muscles according to a similar principle: that a coiled-up substance can stretch like a muscle. The idea was developed by Ray Baughman and his colleagues at the University of Texas at Dallas, who found that twisting up even a simple material like sewing thread or fishing line can create a muscle-like structure that, for its size, can lift weights 100 times heavier than human muscle can manage.

Now, Baughman’s team have developed stronger fibres, using similarly inexpensive materials. Bamboo or silk, for example, are twisted into a coil and coated with a sheath that can respond to heat or electrochemical changes, which can trigger the resulting muscle to contract and move.


The team hope that their materials can be used in smart clothing that responds to the weather. In one experiment, they knitted the fibres into a textile that, as a result, responds to moisture by becoming more porous. “You could imagine such a textile could be more open or more insulating,” says Sameh Tawfick at the University of Illinois at Urbana-Champaign.

Jinkai Yuan at the University of Bordeaux and his colleagues created their fibres using a polymer and graphene – a material stronger than diamond. Mehmet Kanik at Massachusetts Institute of Technology took a different approach. His team developed a material that coils spontaneously, like the tendrils of a cucumber plant. They tested the muscle in a miniature artificial bicep based on a human arm, which lifts a weight when heat is applied.

Engineers still have some way to go to make artificial muscles as efficient as human ones. Currently, only around 3 per cent of the energy put into artificial muscles is used by the fibres, while the rest is lost as heat, says Tawfick. Once this problem has been cracked, he hopes that these artificial muscles, and others like them, could provide cheap and slimline alternatives to the bulky electric motors used to power many devices today.

Journal reference: Science, DOI: 10.1126/science.aaw3722, 10.1126/science.aaw2403, 10.1126/science.aaw2502

We have corrected Ray Baughman’s affiliation.