A Bioinspired and Hierarchically Structured Shape-Memory Material

Abstract

Shape memory polymeric materials lack long-range molecular order enabling more controlled and efficient actuation mechanisms. Here, we develop a hierarchical structured keratin-based system that has long-range molecular order and shape memory properties in response to hydration. We explore the metastable reconfiguration of keratin secondary structure – alpha-helix-to-beta-sheet transition – as an actuation mechanism to design a high-strength shape memory material that is biocompatible and processable through fiber spinning and 3D printing. We extract keratin protofibrils from animal hair and subject them to shear stress to induce their self-organization into a nematic phase, which recapitulates the native hierarchical organization of the protein. This self-assembly process can be tuned to create materials with desired anisotropic structuring and responsiveness. Our combination of bottom-up assembly and top-down manufacturing allows for the scalable fabrication of strong and hierarchically structured shape memory fibers and 3D printed scaffolds with potential applications in bioengineering and smart textiles.