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Hydrogels have been the focus of extensive research due to their potential use in fields including biomedical, pharmaceutical, biosensors, and cosmetics. However, the general weak mechanical properties of hydrogels limit their utility. Here, we generate pristine silk fibroin (SF) hydrogels with excellent mechanical properties via a binary solvent induced conformation transition (BSICT) strategy. In this method, the conformational transition of SF is regulated by moderate binary solvent diffusion and SF/solvent interactions. β-sheet formation serves as the physical crosslinks that connect disparate protein chains to form continuous 3D hydrogel networks, avoiding complex chemical and/or physical treatments. The Young's modulus of these new BSICT-silk fibroin hydrogels can reach up to 6.5±0.2 MPa, tens to hundreds of times higher than that of conventional hydrogels (0.01-0.1 MPa). These new materials filled the "empty soft materials space" in the elastic modulus/strain Ashby plot. More remarkably, the BSICT-SF hydrogels can be processed into different constructions through different polymer and/or metal based processing techniques, such as molding, laser cutting, and machining. Thus, these new hydrogel systems exhibit potential utility in many biomedical and engineering fields.
Zhu et al. (Mon,) studied this question.