An international team of researchers said Thursday they have successfully used fibers, 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 surprising 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 US dollars per kilogram, 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.

The researchers said the muscles could be used for applications where superhuman strengths are sought, such as robots and exoskeletons. Twisting together a bundle of polyethylene fishing lines, whose total diameter is only about 10 times larger than a human hair, produces a coiled polymer muscle that can lift 16 pounds (about 7.3 kilograms). 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.

Meanwhile, independently operated coiled polymer muscles having a diameter less than a human hair could bring life-like facial expressions to humanoid companion robots for the elderly and dexterous capabilities for minimally invasive robotic microsurgery.

Also, they could power miniature "laboratories on a chip," as well as devices for communicating the sense of touch from sensors on a remote robotic hand to a human hand, the researchers said.

These new artificial muscles can be triggered by a number of things, including temperature. Li said they have used the muscles to successfully make "smart textiles" whose pores reversibly open and close with changes in temperature.

The researchers have also demonstrated the feasibility of using environmentally powered muscles to automatically open and close the windows of greenhouses or buildings in response to ambient temperature changes, thereby eliminating the need for electricity or noisy and costly motors, she added.