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 α-helix to β-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.
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All produced data that support this study are included in this published article and its supplementary information files. Data points for the mechanical tests are provided as source data files. Additional data are available from the corresponding author upon request. Source data are provided with this paper.
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We thank the Wyss Institute for Biologically Inspired Engineering at Harvard University for ongoing support throughout this project. We also thank the Center for Nanoscale Systems at Harvard University, in particular S. Stoilova-McPhie and A. McClelland for their assistance in the use of the cryo-TEM and Raman spectrometer, respectively. The Center for Nanoscale Systems is a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation under award no. 1541959. This work was partially funded by the Materials Research Science and Engineering Center of Harvard University under National Science Foundation award no. DMR-1420570. We thank the X-ray Diffraction Shared Experimental Facility at the Massachusetts Institute of Technology, and in particular C. Settens for his assistance during the WAXS experiments. We thank M. Rosnach for his graphic design support. SAXS experiments were supported by the Korean Atomic Energy Research Institute through National Research Foundation grant nos. 2017M2A2A6A01071190 and 2018R1A2B3001690. Finally, we acknowledge the financial support from the Basic Science Research Program of the National Research Foundation (grant nos. 2018R1A6A1A03024940 and 2019R1A2C2084638), which is funded by the Ministry of Science and ICT (Information and Communication Technology) of Korea.
The authors declare no competing interests.
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Cera, L., Gonzalez, G.M., Liu, Q. et al. A bioinspired and hierarchically structured shape-memory material. Nat. Mater. 20, 242–249 (2021). https://doi.org/10.1038/s41563-020-0789-2
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