BSTRACTMoisture change in the clothing system caused by perspiration may be used as a stimulus for smart textiles in a variety of applications. Here we report a water-responsive coil-shaped artificial muscle produced from time-proven

low-cost viscose fibers without chemical modification. Crystallinity of the viscose fiber is a key factor to the actuation performance of the final artificial muscle. The viscose fiber artificial muscle can generate a 35% contraction and a force many times greater than animal skeletal muscles of the same weight. The structural parameters and fabrication conditions were optimized to improve the performance of the coil-shaped artificial muscle.