Strong tough hydrogels via the synergy of freeze‑casting and salting out

This study introduced a freezing-assisted salting-out strategy to fabricate hierarchically structured poly(vinyl alcohol) (PVA) hydrogels that combine high strength, extreme stretchability, exceptional toughness, and outstanding fatigue resistance at water contents of 70–95%. Directional freeze-casting created aligned micrometer-scale pore walls, while subsequent salting-out induced strong polymer aggregation and nanofibril network formation. The resulting hydrogels achieved ultimate stresses up to 23.5 MPa, strains exceeding 2,900%, toughness values above 200 MJ m⁻³, and fatigue thresholds surpassing 10 kJ m⁻², outperforming most reported tough hydrogels and even rivaling natural tendon. The work establishes hierarchical structural engineering as a powerful route for producing load-bearing hydrogels suitable for demanding mechanical environments.