A bioinspired and hierarchically structured shape-memory material

Shape-memory polymeric materials lack long-range molecular order that enables 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 the keratin secondary structure, the transition from alpha-helix to beta-sheet, as an actuation mechanism to design a high-strength shape-memory material that is biocompatible and processable through fibre spinning and three-dimensional (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 fibres and 3D-printed scaffolds with potential applications in bioengineering and smart textiles. Shear-aligned keratin protofibres are used to fabricate shape-memory fibres and three-dimensional scaffolds that respond to water.

Automated summary

The newly developed shape-memory material based on keratin responds to hydration, has high strength and biocompatibility, and is suitable for fiber spinning and 3D printing. By extracting keratin protofibrils from animal hair and applying shear stress, the self-assembly of this hierarchically structured material is achieved.