Sequentially Coupled Thermal-Ionic Modulation for Constructing Robust Muscle-Like Hierarchical Hydrogels

Emulating the multi-scale hierarchical structures of muscles offers a promising approach for constructing mechanically robust hydrogels. However, engineering two structurally distinct architectures across micro-to-mesoscopic length scales via simple, sustainable, and widely applicable approaches remains challenging. Herein, we developed a sequentially coupled thermal-ionic modulation strategy to fabricate robust muscle-like hydrogel nanocomposites with mesoscale anisotropic and microscale hierarchical architectures simultaneously. The first-tier mesoscale anisotropic hydrogel matrix was induced by controlled temperature gradient under thermally asymmetric cyclic freeze-thaw process via a conductive/insulative design of gelation condition. The second-tier microscale hierarchical architecture was further precisely generated by Hofmeister effect mediated ionic salting-out treatment. This sequentially coupled thermal-ionic modulation strategy, combined with nanoparticle-assisted interfacial reinforcement, enables sustainable fabrication of robust muscle-like hydrogel nanocomposite to achieve improved mechanical performance including 10.12 MPa ultimate strength, 512% failure strain, 23.24 MJ/m³ toughness, 26.56 kJ/m² fracture energy, and 16.87 kJ/m² fatigue threshold. This work provides a practical route for constructing mechanically robust biomimetic materials with potential applications in load-bearing biomaterials and fatigue-resistant flexible electronics.