Astral hydrogels mimic tissue mechanics by aster-aster interpenetration

Many soft tissues are compression-stiffening and extension-softening in response to axial strains, but common hydrogels are either inert (for ideal chains) or tissue-opposite (for semiflexible polymers). Herein, we report a class of astral hydrogels that are structurally distinct from tissues but mechanically tissue-like. Specifically, hierarchical self-assembly of amphiphilic gemini molecules produces radial asters with a common core and divergently growing, semiflexible ribbons; adjacent asters moderately interpenetrate each other via interlacement of their peripheral ribbons to form a gel network. Resembling tissues, the astral gels stiffen in compression and soften in extension with all the experimental data across different gel compositions collapsing onto a single master curve. We put forward a minimal model to reproduce the master curve quantitatively, underlying the determinant role of aster-aster interpenetration. Compression significantly expands the interpenetration region, during which the number of effective crosslinks is increased and the network strengthened, while extension does the opposite. Looking forward, we expect this unique mechanism of interpenetration to provide a fresh perspective for designing and constructing mechanically tissue-like materials. The development of tissue-like materials which replicate the mechanical properties of tissue is of interest for a range of applications. Here, the authors report on the development of radial asters that form a gel network to stiffen in compression and soften in extension, resembling tissue mechanics.

Automated summary

The authors report on a unique class of astral hydrogels that exhibit compression-stiffening and extension-softening behavior similar to tissues. These hydrogels are formed through hierarchical self-assembly of amphiphilic gemini molecules, with radial asters that interpenetrate to form a gel network. The mechanism of aster-aster interpenetration in these gels is highlighted as a potential new perspective for designing mechanically tissue-like materials.