Twisted Threads Make Strong, Supple Robots

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The current generation of robots always seem so, well, robotic. Their herky-jerky movements are the result of the stiff wires and pulleys that contract and expand to move their limbs. But what if robo-muscles were more like our own; strong, yet supple, self-sufficient for long periods of time (think of the human battery life versus a robot’s) and able to make complex fine motor movements like writing or sewing.

Scientists say they’ve figured out a simple way to build such muscles using nothing more than nylon fishing line and thread. The secret: twisting the material until it becomes super-strong.

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“They are so simple to make,” said Ray Baughman, professor of chemistry at the University of Texas at Dallas and an author on the paper appearing today in the journal Science. “High school students can pick this up.”

Baughman and his team had previously built artificial muscles using carbon nanotubes, slender chains of carbon molecules that are also super-strong. But over the years, he found that simple nylon line and sewing thread works just as well and is a lot cheaper.

“For our previous artificial muscles, we had to use special nanotubes and spinning techniques that meant people around the world couldn’t do it. Here, young people can make these muscles easily and deploy them.”

The team, which included researchers from Canada, Australia and China, says the polymer muscles are 100 times stronger than human muscles and have the power output of an automobile engine. They contract and relax in response to temperature changes that are controlled by a heating element. The goal is to use them to build low-cost robots and prosthetic devices, according to Baughman.

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He noted that the nylon material they used costs $5 per kilogram, compared to $4,000 to $5,000 per kilogram for similar nickel-titanium wires often used in existing robotic muscle devices. The twisted nylon muscles could also be used in clothing with fabric that could open and close automatically in response to heat or cold, or adjust greenhouse glass windows instead of using motors and electricity.

“There’s no obstacle,” Baughman told Discovery News. “It’s the first time in my life that I’m able to say this. The difficult thing, making the nylon fibers, has already been done.”

One expert says there are no scientific show-stoppers in getting these new twisty nylon yarn muscles into commercialization.

“The numbers are impressive, in terms of what they managed to measure and it is not using an exotic material, but a material well-established, not expensive and in production for years,” said Yoshi Bar-Cohen, a senior research scientist at NASA’s Jet Propulsion Laboratory. “It looks like something you could mass produce.”