ABSTRACT
Silk fibers constitute a class of protein building blocks capable of functionalization and reprocessing into various material formats. The properties of these fibers are typically affected by the intense thermal treatments needed to remove the sericin gum coating layer. Additionally, their mechanical characteristics are often misinterpreted by assuming the cross-sectional area is a perfect circle. The thermal treatments impact not only the mechanics of the fibers but also the structure of the resolubilized protein, thereby limiting the performance of the resulting silk-based materials. To mitigate these limitations, we explored varying alkali conditions at low temperatures for surface treatment, effectively removing the sericin gum layer while preserving the molecular structure of the fibroin protein, thus, maintaining the hierarchical integrity of the exposed fibroin microfiber core. The precise determination of the initial CSA of the asymmetrical silk fibers led to a comprehensive analysis of their mechanical properties. Our findings indicate that the alkali surface treatment raised the Young's modulus and tensile strength by increasing the fibers' crystallinity by approximately 40% and 50%, respectively, without compromising their strain. We have shown that this treatment facilitated further production of high-purity soluble silk with rheological and self-assembly characteristics comparable to those of native silk.
