Carbon Nanotubes Facilitate Silk Hierarchical Assembly by Dry Drawing

Biologically derived hierarchical structural materials not only boast energy-efficient processing but also exhibit impressive mechanical performance. Silk stands as the gold standard in hierarchical fiber production, leveraging a unique combination of advantages. Nevertheless, the artificial replication of silk poses technical challenges related to precision processing and comprehensive molecular control. To address such issues, this study investigates the hierarchical assembly of solid regenerated silk in an air atmosphere, facilitated by the incorporation of carbon nanotube (CNT) seeding. Results obtained highlight that this CNT seeding facilitates multiscale structure development in response to post-spin tensile stress. Such CNT bridged structure assembly bypasses some natural processing control variables (pH, ions) and the necessary solvent immersed state for conventional silk post-drawing. Combining secondary electron hyperspectral imaging and 3D synchrotron X-ray ptychotomography, this study reports silk protein conversion from a disordered as-spun state to a longitudinal orientated semi-crystalline nano structure during drawing. The development of microscale structure during the drawing process is attributed to the presence of CNTs, yielding mechanical properties comparable to, and frequently surpassing, those exhibited by native fibers. These findings collectively propose a framework for exploring novel processing routes and offer a practical means controlling self-assembly in silk materials.