Strain stiffening and compression-induced softening of composite fibrous hydrogels derived from rod-shaped nanoparticles and a synthetic copolymer

Biological fibrous networks exhibit a unique nonlinear response to deformation, that is, they stiffen under shear or elongational strains and soften under weak normal compression. Since these properties impact cell fate and may reflect pathological conditions, man-made fibrous gels can serve as an effective in vitro platform for studying the mechanical properties of biological tissues. Herein, we report an engineered fibrous hydrogel formed by the covalent crosslinking of rod-shape nanoparticles with a random copolymer. The variation in the copolymer composition led to a different degree of intrafibrillar crosslinking and broad-range variation in nonlinear mechanics of the hydrogel, which were not complemented by the change in gel structure. The hydrogel exhibited the properties of athermal enthalpic networks, in agreement with theoretical predictions. This work provides the ability to control nonlinear mechanical properties of fibrous hydrogels in disease modeling and in bioengineering.