Fatigue Resistant Hydrogels Engineered With Twisting Hierarchical Structures

Abstract

Hydrogels hold significant potential for soft robotics and biomedical applications due to their high-water content, tissue-like softness, and biocompatibility, yet their practical utility remains limited by poor fatigue resistance during long-term dynamic loading. Here, we present a twisting strategy that enhances hydrogel materials' mechanical durability through bioinspired torsion methodology, enabling efficient load transfer and energy dissipation. The resulting fibers exhibit improved tensile strength, stretchability, and unprecedented fatigue thresholds while maintaining structural integrity across prolonged cycling. Our strategy is also compatible with various hydrogel systems including poly(vinyl alcohol), alginate, cellulose and corresponding composite systems. This approach benefits from multiscale simulations, revealing that moderate twisting promotes uniform stress distribution through inter-fiber sliding, while excessive twisting causes geometric locking. Proof-of-concept demonstrations include a frog-tongue-inspired actuator showing rapid yet reversible motion under high-frequency cycling, highlighting its exceptional fatigue tolerance. This bioinspired architecture establishes a universal design paradigm for fatigue-resistant hydrogel systems, unlocking their potential in demanding applications from implantable medical devices to adaptive soft robotics.