Natural plant fibers such as cotton have favorable performance in water and moisture management; however, they suffer from inferior processing ability due to limited diameter and length, as well as natural defects. Although commercially available regenerated cellulose fibers such as lyocell fibers can have tunable structures, they rely on the complete dissolution of cellulose molecules, including the highly crystalline parts, leading to inferior mechanical properties. Through a specially designed coaxial wet-spinning process, we prepare a type of hollow fiber using only cellulose nanofibrils (CNFs) as building blocks. It mimics cotton fibers with a lumen structure but with a tunable diameter and a long length. Moreover, such hollow fibers have superior mechanical properties with a Young's modulus of 24.7 GPa and tensile strength of 341 MPa, surpassing lyocell fibers and most wet-spun CNF-based fibers. Importantly, they have 10 times higher wicking ability, wetting rate, drying rate, and maximum wetting ratio compared to lyocell fibers. Together with a superior long-term performance after 500 rounds of wetting-drying tests, such CNF-based hollow fibers are sustainable choices for advanced textile applications. And this study provides a greater understanding of nanoscale building blocks and their assembled macromaterials, which may help to reveal the magic hierarchical design of natural materials, in this case, plant fibers.
Keywords: hollow fiber; moisture sorption and desorption; nanocellulose; wet-spinning; wetting.