Early insights into the unique structure and properties of native silk suggested that β-sheet nanocrystallites in silk would degrade prior to melting when subjected to thermal processing. Since then, canonical approaches for fabricating silk-based materials typically involve solution-derived processing methods, which have inherent limitations with respect to silk protein solubility and stability in solution, and time and cost efficiency. Here we report a thermal processing method for the direct solid-state moulding of regenerated silk into bulk ‘parts’ or devices with tunable mechanical properties. At elevated temperature and pressure, regenerated amorphous silk nanomaterials with ultralow β-sheet content undergo thermal fusion via molecular rearrangement and self-assembly assisted by bound water to form a robust bulk material that retains biocompatibility, degradability and machinability. This technique reverses presumptions about the limitations of direct thermal processing of silk into a wide range of new material formats and composite materials with tailored properties and functionalities.
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The authors declare that all data supporting the findings of this study are available within the paper and its Supplementary Information files and from the corresponding author upon reasonable request.
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This work was supported by grants from the National Institutes of Health (R01AR068048, R01DE016525), the Air Force Office of Scientific Research (FA9550-17-1-0333) and the Stepping Strong Foundation, Brigham and Women’s Hospital (A. Nazarian and G. Dyer). We thank J. Yarger, B. Cherry and N. Sisco at Arizona State University for help with NMR instrumentation and data collection. We thank G. Dyer for clinical relevance discussions. We also thank S. Maccorkle and D. Dupuis at the Tufts University Machine Shop for materials machining.
The authors declare no competing interests.
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Guo, C., Li, C., Vu, H.V. et al. Thermoplastic moulding of regenerated silk. Nat. Mater. 19, 102–108 (2020) doi:10.1038/s41563-019-0560-8