L. Wu, Y. Kang, X.Y. Shi, Y.Z. Bin, M.J. Qu, J.Y. Li, Z.-S. Wu*

ACS Nano, 2023, 17.

DOI: 10.1021/acsnano.3c01976 [PDF]

Hydrogels are able to mimic the flexibility of biological tissues or skin, but they can’t still achieve satisfactory strength and toughness, greatly limiting their scope of application. Natural wood can offer the inspiration for designing high-strength hydrogels attributed to its unique anisotropic structure. Herein, we propose an integrated strategy for efficient preparation of ultra-strong hydrogels using a salting-assisted pre-stretching treatment. The as-prepared polyvinyl alcohol/cellulose nanofiber hybrid hydrogels show distinct wood-like anisotropy, including oriented molecular fiber bundles and extended grain size, which endows materials with extraordinarily comprehensive mechanical properties of ultimate breaking strength exceeding 40 MPa, strain approaching 250% and toughness exceeding 60 MJ·m-3, and outstanding tear resistance. Impressively, the breaking strength and toughness of the re-swollen pre-oriented hydrogels approach 10 MPa and 25 MJ·m-3, respectively. And, in vitro and in vivo tests demonstrate that the re-swollen hydrogels don’t affect the growth and viability of the cells, nor do it cause the inflammation or rejection of the mouse tissue, implying extremely low biotoxicity and perfect histocompatibility, showcasing bright prospects for application in artificial ligaments or tendons. This strategy provided in this study can be generalized to a variety of biocompatible polymers for the fabrication of high-performance hydrogels with anisotropic structures.