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.The current mechanism of interpenetration is fundamentally different from the mechanism of cell-or particle-inclusion proposed for tissues or hybrid tissue mimics.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,this unique mechanism of interpenetration might provide a new perspective for designing and constructing mechanically tissue-like materials。interpenetrative matter that could emerge as a new class of materials appealing in geometry and mechanical properties.Thus,a new type of material with attractive geometrical and mechanical properties is designed.