A recent discovery by an international team of researchers led by the University of Texas at Dallas has resulted in the development of inexpensive, powerful synthetic muscles using fishing line and sewing thread. Scientists at UT Dallas’s Alan G. MacDiarmid NanoTech Institute teamed with scientists from universities in Australia, South Korea, Canada, Turkey and China to accomplish the advances.
Testing shows that the new muscles can pick up a hundred times more weight and generate a hundred times higher mechanical power than the same length and weight of human muscle. Per weight, the synthetic muscle can generate 7.1 horsepower per kilogram, roughly the same mechanical power delivered by a jet engine.
The finding appears February 21 in the journal Science, in which researchers describe that the synthetic muscles are produced by twisting and coiling high-strength polymer fishing line and sewing thread.
The muscles are powered by temperature changes, which can be produced electrically, by the absorption of light or by the chemical reaction of fuels. Twisting the polymer fiber converts it to a torsional muscle that can spin a heavy rotor to more than 10,000 revolutions per minute. Additional twisting, so that the polymer fiber coils like a heavily twisted rubber band, produces a muscle that radically contracts along its length when heated, and returns to its initial length when cooled. If coiling is in a different twist direction than the initial polymer fiber twist, the muscles instead expand when heated.
In comparison to natural muscles, which contract by about 20 percent, these new synthetic 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 application opportunities for these polymer muscles are vast,” said corresponding author Dr. Ray Baughman, the Robert A. Welch Distinguished Chair in Chemistry at UT Dallas and director of the NanoTech Institute. “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 and colleagues previously wrote about the promise of synthetic muscles in a November 16, 2012 report in Science, titled “Electrically, Chemically, and Photonically Powered Torsional and Tensile Actuation of Hybrid Carbon Nanotube Yarn Muscles.” In it, Baughman and colleagues highlighted the commercial viability of the development of synthetic muscles, and laid the groundwork for future exploitation of the benefits of their use.