They're small but mighty. The tiny artificial muscles created by an international team of researchers are 200 times stronger than human muscle fibers of comparable size.
In the future, improved versions of the muscles could go into the next generation of motors for robots arms, flaps on airplane wings, medical devices — any inanimate thing that moves.
"There's a lot of excitement," said Richard Vaia, who studies high-tech materials at the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio. Vaia was not involved in the making of the new muscle.
Researchers around the world have been trying to create artificial muscles that work more the way natural muscles do, to allow for more-delicate movements than current mechanisms can achieve.
Ray Baughman, a nanotechnology researcher at the University of Texas at Dallas, led the team that made the new muscle, which he sometimes calls a yarn because of the way it's woven. The muscles would work well in small medical devices, he said. His lab in Texas has thought of another creative use for them, too: "We've been playing with yarns to open and close blinds depending on the temperature of the room," he told TechNewsDaily.
In the farther future, artificial muscles could give robots more natural-looking facial expressions, Baughman said.
The lab wants to try to manufacture longer ropes of the muscle, so it can weave a protective fabric for firefighters' uniforms. The fabric would automatically seal its pores when faced with a sudden flash, Baughman said.
Baughman's new muscles are made of ropes of carbon nanotubes, a super-tiny, high-tech material that researchers are adding to everything from water filters to experimental airplane parts. Baughman said he and his team twisted the nanotubes — "quite similarly to the way people insert twists into common wool or cotton fibers" — into thicker yarns. They then filled the hollow space in the nanotubes with different materials, including paraffin, the wax that goes in candles.
To get the muscles to contract, researchers heated them briefly. When heated, the paraffin wax expanded, pushing against the nanotube walls and making them fatter and shorter. As the wax cooled again, it shrank, and the nanotubes became narrower and longer. The muscles were able to shorten and then lengthen again every 25 milliseconds, or 25 thousandths of a second, Baughman said. Such fast contractions mean the muscles are able to perform a lot of work, he said.
The combination of carbon nanotubes and wax impresses Vaia. "The novel thing was how they utilized the properties of the two, came up with the correct processing to put them together," he said.
Fabrics for the future
Right now, Baughman's lab knows how to make a muscle fiber that's one kilometer (0.62 miles) long, but Baughman hopes one day to weave fabrics that require miles of fiber.
He also is looking to make the muscles react to chemicals instead of heat. Heat-driven motors are energy-inefficient, so chemical-driven muscles might be more practical.
Baughman and his colleagues wrote about their work today (Nov. 15) in the journal Science.