Structural biomimetics in soft synthetic composite materials: A proof-of-concept alginate-polyamide soft hierarchical composite

Natural materials often consist of hierarchical architectures, which are extremely efficient in mechanical terms. Whereas the structure-function relationship is well-studied in natural hard materials, soft materials are not getting equal attention, despite their high prevalence in nature. These soft materials are usually constructed as fiber-reinforced composites consisting of diverse structural motifs that result in an overall unique mechanical behavior. In this study, as a proof-of-concept, a soft biomimetic composite was fabricated from a hierarchical electrospun polyamide fiber, reinforcing a hydrogel matrix and creating a simple synthetic analog for natural soft composites. This material system investigates the structure-function relationship between the structure and mechanical function by mimicking different structural motifs. The polyamide-hydrogel composite exhibited large deformations and nonlinear material behavior. Varying degrees of crimping enabled a controlled strain stiffening behavior and engineered transition from matrix-dominated to fiber-dominated behavior. We also observed that the individual nanofibers in our bundles created cross-bridges with the matrix and within the bundle, making the material system more resistant to failure. Our bio-inspired composite demonstrated mechanical behaviors similar to natural soft composites, which can aid in the future design and development of the next generation of soft architectural composites.

Automated summary

Natural materials often have hierarchical architectures that are efficient in mechanical terms. This study focused on a biomimetic composite made from polyamide fibers and a hydrogel matrix, mimicking the structure and mechanical function of natural soft composites. The composite exhibited large deformations and nonlinear material behavior, with controlled strain stiffening and transition between matrix-dominated and fiber-dominated behavior. The bio-inspired composite showed mechanical behaviors similar to natural soft composites, providing insights for the future design of soft architectural composites.