Artificial Muscles from Fishing Line and Sewing Thread

TLDR

High‑cost, large‑stroke artificial muscles suffer from low cycle life, hysteresis, and inefficiency, limiting their practical use. We showed that inexpensive high‑strength fishing line and sewing thread, when twisted, form fast, scalable, nonhysteretic, long‑life tensile and torsional muscles that can contract 49 %, lift loads over 100 × heavier than comparable human muscle, and deliver 5.3 kW kg⁻¹, while also enabling temperature‑responsive textiles and energy‑saving window shutters, with large‑stroke actuation arising from torsional motion.

Abstract

The high cost of powerful, large-stroke, high-stress artificial muscles has combined with performance limitations such as low cycle life, hysteresis, and low efficiency to restrict applications. We demonstrated that inexpensive high-strength polymer fibers used for fishing line and sewing thread can be easily transformed by twist insertion to provide fast, scalable, nonhysteretic, long-life tensile and torsional muscles. Extreme twisting produces coiled muscles that can contract by 49%, lift loads over 100 times heavier than can human muscle of the same length and weight, and generate 5.3 kilowatts of mechanical work per kilogram of muscle weight, similar to that produced by a jet engine. Woven textiles that change porosity in response to temperature and actuating window shutters that could help conserve energy were also demonstrated. Large-stroke tensile actuation was theoretically and experimentally shown to result from torsional actuation.