Spinning fishing line and sewing thread into artificial muscle

Researchers have transformed everyday plastic fibers into super strong artificial muscles just by twisting them like rubber bands until they coil up.

Since these materials are cheaper than high-tech shape memory alloys and carbon nanotubes, the new technology could soon be widely applied, from robotics and prosthetics to clothing that adjusts to your temperature.


To be clear, the muscles I’m talking about are actuators, powerful rotating motors. Science explains:

The term “artificial muscles” is actually a bit of a grab bag that refers to materials that 

• contract, 
• expand, or
•  rotate 

when 

• heated, 
• zapped with electricity, or 
• hit with some other stimulus. 

The materials return to their original shape when the stimulus is reversed.
An international team of researchers led by Ray Baughman of University of Texas at Dallas wanted to twist plastic fibers and threads into yarn. Their “extreme twisting” of high-strength polymer fibers -- found in ordinary items such as fishing lines and sewing threads -- allowed the coiled plastic yarn to act like torsional muscles that can lift loads 100 times heavier than human muscles of the same length and weight.

Specifically, these muscles are powered by temperature changes: They contract lengthwise when heated and return to their initial length when cooled. Compared to natural muscles -- which contract by about 20 percent -- these new muscles contract by up to 50 percent of their length. Per weight, they can generate about the same mechanical power as a jet engine.

“Today’s most advanced humanoid robots, prosthetic limbs and wearable exoskeletons are limited by motors and hydraulic systems, whose size and weight restrict dexterity, force generation and work capability,” Baughman says in a news release. These muscles can be used whenever superhuman strengths are needed, cheaply. Producing this force, Science reports, requires only off-the-shelf materials that cost about $5 per kilogram (or $10 a pound). According to the release:

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. Operated in parallel, similar to how natural muscles are configured, 100 of these polymer muscles could lift about 1,600 pounds.

Here’s a cool video of the artificial muscle lifting weights:

On a smaller scale, they’ve woven textiles from the twisted yarns of polymer that can adjust to temperature changes. That means clothing that opens its pores to keep you cool and close them to warm you up, as well as window shutters that open and close to keep the temperature comfortable.


The work was published in Science this week.


Read more: UT Dallas news release, UBC release, Science, Popular Mechanics
Images: Science/AAAS (top) and University of Texas at Dallas (thumbnail)

ORIGINAL: Smart Planet

By Janet Fang

February 21, 2014