Porous hierarchically ordered hydrogels demonstrating structurally dependent mechanical properties.

Abstract

While hierarchical ordering is a distinctive feature of natural tissues and is directly responsible for their diverse and unique properties, efforts to synthesize biomaterials have primarily focused on using molecular-based approaches with little emphasis on multiscale structure. Here, we report a bottom-up self-assembly process to produce highly porous hydrogel fibers that resemble extracellular matrices both structurally and mechanically. Physically crosslinked nanostructured micelles form the walls of micrometer-sized water-rich pores with preferred orientation along the fiber direction. Low elastic moduli (<1 kPa), high elasticity (extending by more than 12 times the initial length), non-linear elasticity (e.g., hyperelasticity), and completely reversible extension are derived from unevenly distributed strain between the micrometer-sized pores and the polymer chains, which is reminiscent of cellular solids. Control of the material microstructure and orientation over many orders of magnitude (e.g., nm-μm), while holding the nanostructure constant, reveals how the multiscale structure directly impacts mechanical properties.