Bioinspired Tough and Strong Hierarchical Fibers with Controlled Structure
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Protein fibers occupy an increasingly important position in military, civilian, and medical applications. Spider dragline silk with a hierarchical structure exhibits a unique combination of mechanical strength, toughness and energy absorption, but it’s hard to apply due to its low output. And it’s difficult to produce protein fibers with mechanical properties comparable to spider dragline silk. In this work, taking regenerated silk fibroin (RSF) as outer phase while the reinforcement cellulose nanofibrils (CNFs) as inner phase, a hierarchical fiber with a core-shell structure is prepared in situ continuously by adopting a co-axial microfluidic device. The hierarchical CNF/RSF core-shell fiber also gets a unique trade-off in tensile strength and toughness. By adjusting the core and shell flow rate ratios, the morphology of the core-shell fiber and the mechanical properties are tunable. A proper post-stretching treatment makes the core-shell fiber a more orderly molecular arrangement, thus improving its mechanical properties. And it can maintain its mechanical properties even at -30℃. Moreover, a net woven by as-spun core-shell fibers can not only bear a static load but also can easily withstand a free fall impact load without any breakage. This work opens an avenue towards the preparation of artificial spider dragline silk with applications in dynamic energy buffering and shock-absorbing, making the obtained superfine core-shell fiber a candidate material for advanced structural materials.