Fatigue-Resistant Liquid Crystal Elastomer/Polyurethane Composite Fibers with Hydrogen-Bond-Reinforced Two-Phase Microstructures

Liquid crystal elastomers (LCEs) are promising for soft robotics and smart textiles, but they are limited by low mechanical strength and poor fatigue durability. Here, we report a continuous wet-spinning strategy with potential scalability for fabricating fatigue-resistant liquid crystal elastomer/polyurethane (LCE/PU) composite fibers by incorporating a thiol-functionalized waterborne PU into the LCE matrix. The resulting fibers form a unique two-phase microstructure reinforced by interfacial covalent coupling and hydrogen-bond-mediated interactions at the LCE/PU interface, which significantly enhance the fibers’ mechanical integrity. By optimizing the PU content, the composite fiber with 30 wt % PU (denoted LCE/PU-30) exhibits a tensile strength of 15.9 MPa (approximately 50 cN), representing an ∼56% improvement over the pure LCE fiber. Furthermore, the composite fiber demonstrates significantly enhanced fatigue resistance, withstanding over 450 cyclic actuations with minimal performance degradation. Importantly, the composite fibers retained thermoresponsive actuation behavior while exhibiting enhanced mechanical robustness. As a proof-of-concept demonstration, an artificial lung lobe device constructed with LCE/PU-30 fibers exhibited a qualitative breathing-like motion under thermal stimuli. This work provides a feasible materials-design strategy for improving the mechanical robustness and cyclic durability of LCE-based fibers and supports their potential use in fatigue-resistant soft actuators and smart textile systems.