Natural soft tissues often exhibit amazing behaviors that are difficult to replicate with synthetic materials. For instance, cartilage, artery walls, ligaments and other connective tissues, are water-rich yet display high stiffness, strength, and toughness. This combination of properties is originated from a sophisticated self-assembled network of stiff collagen nanofibers and soft biomacromolecules. The re-formable non-covalent interactions between the components allow for re-organization under stress, adapting to body-specific load patterns. Known biomimetic hydrogels with multiple polymer networks, nano-reinforcement, or non-covalent crosslinking are able to replicate some of these structural elements. However, the partial sets of suitable mechanical properties are often acquired at the expense of the water content which is essential for nutrient transport in soft tissues. Here we report water-rich composites constructed from aramid nanofibers (ANFs) interlaced with soft poly(vinyl alcohol) (PVA), which exhibit mechanical properties parallel or superior to those of load-bearing soft tissues, as exemplified by articular cartilage. Hydrogen bonding between the stiff ANF framework and soft PVA chains affords synergistic stiffening and toughening of the nanocomposites. Although their water content is 70%-92%, the composites possess tensile moduli of ~9.1 MPa, ultimate tensile strains of ~325%, and compressive strengths of ~26 MPa. Their fracture toughness can be as high as ~9,200 J/m2, exceeding that of cartilage. Furthermore, the nano-fibrous network self-organizes under stress, adapting itself to allow effective load bearing and viscoelastic energy dissipation. The mechanical behavior, chemical composition and biocompatibility of these biomimetic composites permit their further utilization in biomedical applications.

Biomimetic composite hydrogels with abiotic self-organizing nanofiber network

255th National Meeting (2018)

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