Microbubble‐Mediated Synthesis of Smart Spindle Microfibers for Fog Harvesting

ABSTRACT Fog has significant potential as a water resource, offering a solution for alleviating the global risk of freshwater scarcity. Spindle‐knotted microfibers are highly effective for fog collection, though the complexity of fabricating such structures remains a significant challenge. In this study, a simple microfluidic method using microbubbles is introduced for the fabrication of smart spindle microfibers (SSMs). The combination of microbubbles of varying sizes, induced by pulses from a peristaltic pump, and thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAm)‐based materials facilitated the formation of periodic knots and joint structures with enhanced structural stability and hydrophilic rough surfaces. The spindle‐knotted structure, featuring textured hydrophilic surfaces, extends the three‐phase contact line and maximizes the volume of the collected water droplets. This promotes the rapid detachment of large droplets formed within a short time, thereby enhancing fog harvesting efficiency. This approach achieves a collection rate of 0.046 g min ⁻¹ , representing 161% of the previously reported fog collection efficiency. Moreover, SSMs adjust their wettability across different temperature cycles owing to the thermo‐responsive properties of PNIPAm, ensuring consistent and reliable fog collection efficiency, even under changing environmental conditions. This adaptability provides practical insights that enable efficient large‐scale water harvesting, addressing the urgent need for effective water collection solutions.