@article {1662166, title = {Bioinspired Tough and Strong Fibers with Hierarchical Core-Shell Structure}, journal = {Advanced Materials Interfaces}, volume = {10}, number = {2}, year = {2023}, pages = {2201962}, abstract = { Strong and tough bio-based fibers are attractive for both fundamental research and practical applications. In this work, strong and tough hierarchical core{\textendash}shell fibers with cellulose nanofibrils (CNFs) in the core and regenerated silk fibroins (RSFs) in the shell are designed and prepared, mimicking natural spider silks. CNF/RSF core{\textendash}shell fibers with precisely controlled morphology are continuously wet-spun using a co-axial microfluidic device. Highly-dense non-covalent interactions are introduced between negatively-charged CNFs in the core and positively-charged RSFs in the shell, diminishing the core/shell interface and forming an integral hierarchical fiber. Meanwhile, shearing by microfluidic channels and post-stretching induce a better ordering of CNFs in the core and RSFs in the shell, while ordered CNFs and RSFs are more densely packed, thus facilitating the formation of non-covalent interactions within the fiber matrix. Therefore, CNF/RSF core{\textendash}shell fibers demonstrate excellent mechanical performances; especially after post-stretching, their tensile strength, tensile strain, Young{\textquoteright}s modulus, and toughness are up to 635\ MPa, 22.4\%, 24.0\ GPa, and 110\ MJ m-3, respectively. In addition, their mechanical properties are barely compromised even at -40 and 60 {\textdegree}C. Static load and dynamic impact tests suggest that CNF/RSF core{\textendash}shell fibers are strong and tough, making them suitable for advanced structural materials. }, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202201962}, author = {Xiao, Yao and Yang, Chenjing and Zhai, Xiaowei and Zhao, Lai and Zhao, Peng and Ruan, Jian and Chen, Dong and Weitz, DavidA. and Liu, Kai} }