Fishing-Line Muscles Are Superstrong

An international team of researchers led by Ray Baughman, PhD, of the University of Texas at Dallas has created artificial muscles from ordinary fishing line that are said to be 100 times more powerful than a human muscle of the same weight and length.

The team has published their research, "Artificial muscles from fishing line and sewing thread," in the February 21 issue of the journal Science.

Baughman, who is director of UT Dallas' NanoTech Institute, says that twisting a few strands of fishing line can create a muscle that lifts 16 pounds. Bundles of 100 of these twisted strands can lift up to 1600 pounds, can contract to 49 percent of their initial length, and are said to function for millions of cycles.

The team, which includes scientists from Australia, Canada, China, South Korea, and Turkey, had spent years experimenting with various exotic materials such as carbon nanotubes before discovering that the best material for this application was actually polyethylene fishing line. "Sometimes there is a great irony in research," Geoffrey Spinks, PhD, lead Australian researcher on the project, told the  Australian Research Council (ARC) Centre of Excellence for Electromaterials Science (ACES) website.

The artificial muscles are created by twisting the fishing line until it forms coils. "We attached one end of the fishing line to an electric drill and hung a weight off the other end to apply some tension. We stop the weight from rotating and we use the drill to insert twist into the fiber," explains Spinks. "Before too long, the whole fiber is a spring-like coil. To set this shape, we apply a little bit of heat from a hair dryer and the coil contracts."

Once they have their fishing-line muscles, the researchers just apply heat to make them expand or contract. If the lines are coiled in one direction, they contract when heated. If coiled in the other direction, heat causes them to expand.

The heat can come from any conventional source. Though the researchers used resistive heating, from passing a electric current through a wire or metallic sewing thread, they say that heat from radiant or chemical sources would work just as well.

"The application opportunities for these polymer muscles are vast," says Baughman. "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."

Lead author Carter Haines told the UT Dallas News Center, "We have woven textiles from the polymer muscles whose pores reversibly open and close with changes in temperature. This offers the future possibility of comfort-adjusting clothing," The researchers also hypothesize that building ventilation systems might also be designed that react to changes in ambient temperature to open and close vents.

Stephen Levy is a contributor to Qmed and MPMN.