Enhanced Water Harvesting on Directionally Patterned Slippery Undecylenic‐Modified Cellulose Nanoparticle Surfaces

ABSTRACT Efficient fog harvesting strategies have attracted increasing attention for addressing global water scarcity. In this study, a bio‐inspired slippery surface was engineered by combining hydrophilic–hydrophobic patterning and lubricant infusion based on hydrophobic undecylenic‐modified microcrystalline cellulose (UMCC) nanoparticles. The UMCC nanoparticles were synthesized using a dialysis–spraying process, followed by UV‐assisted patterning of the hydrophilic domains and infusion with a perfluoropolyether lubricant to create a stable, directionally modified slippery interface. The pristine nanoparticle surface exhibited strong adhesion and high contact‐angle hysteresis, which severely hindered droplet removal. However, after lubricant infusion, the contact angle hysteresis was dramatically reduced, enabling rapid droplet mobility, similar to that of Nepenthes pitcher plants. The resulting surface exhibited excellent chemical and environmental stabilities over a wide pH range. Notably, the moderately hydrophilic amino‐patterned surface enhanced droplet nucleation, coalescence, and directional removal, achieving an exceptional fog‐harvesting rate of 532.8 ± 85.1 mg/(h·cm 2 ), surpassing the performance of all unmodified controls. This study established a simple and sustainable platform for next‐generation bio‐inspired fog‐harvesting and water‐management technologies.