An international team of researchers have successfully used fibres, such as those used for fishing lines and sewing threads, to create inexpensive but powerful artificial muscles.
In a paper published in the US journal Science, the team led by the University of Texas and joined by other research institutes from China, Canada, Turkey, Australia and South Korea, described a surprisingly simple way to make the muscles by twisting high-strength polymer fibers until they coil up, just like one would twist the rubber band of a model toy airplane.
"The new muscles are capable of lifting loads 100 times heavier than human muscles of the same length and weight," Li Na, of the University of Texas and one of the authors, told Xinhua. "They can generate 7.1 horsepower per kg of muscle weight, similar to that produced by a jet engine."
According to Li, the idea was based on their previous success of creating muscles using materials like carbon nanotubes as they hoped to bring down the manufacturing cost.
Artificial muscles with similar functions that are made out of nickel-titanium alloys are extremely expensive as these alloys can cost up to $3,000 per kg, while their new muscles only require materials that cost about five dollars per kilogram, Li said.
In their study, Li and her colleagues found that, compared to natural muscles, which contract by only about 20 percent, these muscles can contract by about 50 percent of their length. The muscle strokes also are reversible for millions of cycles as the muscles contract and expand under heavy mechanical loads.
Twisting together a bundle of polyethylene fishing lines, whose total diametre is only about 10 times larger than a human hair, produces a coiled polymer muscle that can lift 16 pounds (about 7.3 kg). Operated in parallel, similar to how natural muscles are configured, a hundred of these polymer muscles could lift about 0.8 tons, the researchers said.