Self-induced large pitch artificial muscles with giant stroke for soft robotic applications

Achieving large initial coil pitches and contractile strokes in twisted and coiled polymer artificial muscles often requires complex and multi-step fabrication processes. We present a self-induced large-pitch (SLiP) method for producing polymer muscles with large and stable initial coil pitches through a single-step annealing process, which can be tuned by only adjusting the annealing temperature and duration. The resulting muscles demonstrate contractile and tensile strains of 95.1% and 560%, respectively, under different chiral configurations, as well as a maximum specific power of 3.5 kW kg^-1and a contractile stroke rate of 40% s^-1. SLiP muscles are used in various biomimetic and soft robotic prototypes, including a biomimetic arm, large-deformation tentacles, a crawling robot, and a biomimetic hand. This method offers a practical route for realizing polymer muscles with giant stroke and preload-free actuation in soft robotics.