Hierarchical crack-resistant, tissue-mimetic hydrogels enabled by progressive nanocrystallization of anisotropic polymer networks
Huamin Li, Haidi Wu, Cheng Guan, Wenjie Hu, Wenwen Su, D. Chen, Jiefeng Gao
Abstract
Abstract Addressing the persistent challenge of reconciling extreme mechanical robustness with tissue-mimetic functionality in hydrogels, we present a phase-transition-guided hierarchical engineering strategy that progressively architectures anisotropic polyvinyl alcohol networks through sequential mechanical training, wet-annealing, and salting-out. This triphasic processing induces programmable structural evolution: (1) mechanical training aligns polymer chains, (2) wet-annealing relaxes the stress while stabilizes oriented crystallites through solvent-plasticized rearrangement, and (3) salting-out densifies the network via chain aggregation and hydrogen-bond proliferation. The resultant hierarchical architecture achieves high fatigue resistance (threshold: 2083 J·m −2 ) through multi-scale energy dissipation: sacrificial hydrogen bonds consume energy, while aligned crystalline domains pin the crack and deflect crack propagation via anisotropic stress redistribution. Demonstrating tissue-surpassing mechanics (tensile strength: 61 ± 3 MPa, toughness: 106 ± 27 MJ·m −3 , fracture energy: 85 ± 9 kJ m −2 ) coupled with biological functionality, the hydrogel directs cell alignment through contact guidance while resisting swelling-induced dimensional instability (<1.2% volume change in physiological saline). This biomimetic engineering strategy establishes a universal route to design synthetic extracellular matrices that concurrently emulate the anisotropic mechanics of tendons and crack-blunting resilience of cartilage, critical for load-bearing tissue regeneration.