Bioinspired Robust Helical-Groove Spindle-Knot Microfibers for Large-Scale Water Collection

Helical structure is ubiquitous in nature with high-order configuration, specific paths, large superficial areas, providing an approach to bioinspired wettability control. Owing to its special hydrophilic rough surfaces and periodic knot and joint structure, natural spider silk can catch tiny droplets in fog and transport them directionally, sparking scientific interest in bioinspired knotted microfibers to address the risk of water scarcity. To further enhance the water collection ability, a bioinspired helical-groove-modified spindle-knot (HSK) microfiber is continuously fabricated in this work by a simple coating method combined with crack regulation. The formation and morphology can be precisely manipulated by adjusting the drawing velocity and concentration of the coating solution. Compared with smooth spindle-knot microfibers, HSK exhibits greater performances of wetting speed, droplets growth rate, and hanging ability, which can be attributed to the unique helical paths that bring capillary force difference and offer extra three-phase contact line lengths for water collection behavior. The maximum droplet volume is almost 2114 times that of the microfiber knots, which is the highest compared with previous reports. Moreover, HSK microfibers are endowed with repairable wettability, long-term durability, excellent mechanical properties, and flexibility, showing great potential in the realm of applications for large-scale water collection.