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Artificial Muscle from Fishing Line: Powerful yet Cheap

When we think of artificial muscles, we tend to think of new materials that allow constructs to replicate the function of organic muscles in useful ways. We don't tend to think of existing materials in common usage as a means to create these muscles. After all if they are in common usage, they would already have been tested and discarded, right?

Not so.

Sewing thread combined with stock, off the shelf fishing line has been used by a research team centring around the University of Texas at Dallas, in Texas USA, to create fully functional, and rather powerful artificial muscles, by approaching these common materials in a new way.

An example showing a thread made out of many individual fishing-line artificial muscles bound together.
Credit: University of Texas at Dallas

The new muscles can lift a hundred times more weight and generate a hundred times higher mechanical power than the same length and weight of human muscle. Per weight, they can generate 7.1 horsepower per kilogram, about the same mechanical power as a jet engine.

All this power was achieved by relying on the natural strength of the material,s, and most importantly, twisting and coiling both high-strength polymer fishing line and sewing thread into a single, tightly bound tendril that forms the basis for the muscle, and is thinner than a human hair.

It turns out the muscle doesn't just have a hundred times the strength of a human muscle of the same length and weight, it is also remarkably more compact. Standard organic muscles as found in humans, can compact up to 20% of their mass as they move. For these artificial muscles that figure is 50%. This enables much more muscle to be packed into the same area, increasing their strength still further. Large numbers of these tendrils can then be again twisted and interwoven together to form larger muscle blocks, in theory thicker than those found in nature because of their ability to compact.

"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."

He likewise sees that there are applications for the individual tendrils, or for small fibre bundles, in working artificial facial muscles and fine delicate tasks.

The polymer muscles are normally electrically powered by resistive heating using the metal coating on commercially available sewing thread or by using metal wires that are twisted together with the muscle. For other applications, however, the muscles can be self-powered by environmental temperature changes, said Carter Haines, lead author of the study. "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," said Haines.

The artificial muscles can be any size from a single thread (right) to the thickness of a pencil (left) and beyond.
Credit: University of Texas at Dallas


The fishing line and thread muscles are still a long way from seeing practical application, but are a serious contender in the ongoing work to create artificial muscles as strong and as resilient as human ones – and stronger if at all possible. The power, weight and cost savings in a muscle-based rather than motor and actuator based approach to movement cannot be overstated. Neither can their importance in bringing lifelike muscle movements to embodied androids and gynoids.


UT Dallas-led team makes powerful muscles from fishing line and sewing thread

Artificial Muscles from Fishing Line and Sewing Thread (Paper, Paywalled)

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