Facile and large-scale fabrication of an efficient Janus fog collector with a cactus trichome-like hydrophilic surface

The fog-collection strategy has garnered widespread attention as a sustainable method to alleviate freshwater scarcity issues in severely arid regions. Janus membranes with asymmetric wettability can provide highly efficient fog-collection owing to their rapid fog-droplet condensation, efficient unidirectional water transport, and timely water droplet shedding. Nevertheless, the construction of Janus membranes with high fog-collection efficiency and excellent durability remains a major challenge. In this study, a facile two-step unilateral spraying strategy was employed to fabricate a Janus membrane (JM-AT) with asymmetric wettability and a cactus trichome-like structure. The cactus trichome-like structure on the hydrophilic (HL) surface consists of rod-like attapulgite (APT) fibers containing abundant hydroxyl groups and HL titanium dioxide (TiO 2 ) nanoparticles, which increase the surface roughness and capillary force and thus significantly enhance wettability. Benefiting from the synergistic effects of the asymmetric wettability and cactus trichome-like structure, JM-AT exhibited an outstanding unidirectional water transport capability and efficient fog-collection (water-collection rate up to 9.74 g cm −2 h −1 ), and it maintained a stable water-collection rate even after 10 fog-collection cycles. In addition, the introduction of an aluminum phosphate inorganic binder allowed the APT and TiO 2 nanoparticles to be firmly adhered to the Cu mesh surface, which provided JM-AT with excellent mechanical and chemical stability. JM-AT prepared via this facile spraying method has considerable potential to alleviate freshwater scarcity issues in arid desert regions and support sustainable agricultural water-retention strategies.