PEER-REVIEWED PUBLICATION

2021

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

Hua M, Wu S, et al.

Nature

University of California – Los Angeles, Shanghai Jiao Tong University, Argonne National Laboratory

RESEARCH SUMMARY

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.

A CellScale UniVert mechanical testing system was used as the primary platform for uniaxial tensile testing and cyclic fatigue testing of the hierarchically aligned PVA hydrogels. The UniVert enabled precise measurement of force–displacement behavior during monotonic stretching to failure, cyclic loading–unloading, and long-term fatigue experiments conducted in a hydrated environment. CellScale-generated stress–strain data were essential for quantifying tensile strength, extensibility, toughness, hysteresis, and fatigue crack growth rates. These measurements formed the experimental backbone of the study, directly validating that the freeze-casting plus salting-out strategy produces hydrogels capable of sustaining large deformations and repeated loading without catastrophic failure.

AUTHORS

Mutian Hua, Shuwang Wu, Yanfei Ma, Yusen Zhao, Zilin Chen, Imri Frenkel, Joseph Strzalka, Hua Zhou, Xinyuan Zhu, Ximin He.

PUBLICATION DETAILS

JOURNAL

Nature

YEAR

2021

INSTITUTIONS

University of California – Los Angeles, Shanghai Jiao Tong University, Argonne National Laboratory

COUNTRIES

China, United States

INSTRUMENT USED

UniVert

TESTING METHODS

Fatigue TestingHydrated and Temperature Controlled TestingTensile TestingViscoelastic & Time-Dependent Testing

RESEARCH APPLICATIONS

Hydrogel Mechanical TestingInjectable & Regenerative BiomaterialsMaterial Fatigue and DurabilityPolymers and Elastomers Testing

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