Self-pumping and scalable fog collector with diode-like micro-hole arrays inspired by natural asymmetric wettability

Abstract Fog collection has been considered as an effective and sustainable approach for relieving the water deficiency in arid regions. Despite great progresses on bioinspired superwetting surfaces towards fog collection, practical fog-collecting devices face challenges by omnidirectional collection and lower-evaporation storage simultaneously. Inspired by unidirectional liquid movement caused by asymmetric wettability on the holey lotus leaf, a self-revolving collector was developed to efficiently harvest the fog in a wind-driven manner, finally storing it lastingly at lower-evaporation rate. Such a collector provided a superhydrophobic external surface for capturing fogdrops, a diode-liquid micro-hole array for the spontaneous droplet movement, and a hydrophilic internal surface for fast droplet collection and long-term storage. The synergy of these structural features together with composition merits made the self-revolving collector show efficient fog collection and lower-evaporation storage. The fog-laden wind field around the collector as well as the relationship between the self-revolving speed and the fog-laden wind speed were explored theoretically. The corresponding model analyses further supported the 49% enhancement of fog collection rate when the collector whipped by 1 m/s fog-laden wind revolves at 18 rad/s. This work opens an avenue for designing a novel fog collector used in real environment and offers a strategy for optimizing the existing fog collectors towards high efficiency.