Bioinspired Janus Mesh with Gradient Wettability for High‐Efficiency Fog Harvesting via Synergistic Capillary Condensation and Directional Droplet Transport

To tackle the challenges of inadequate environmental compatibility and insufficient wettability gradient in the Janus structure used for current fog water collection. This study, inspired by Nepenthes pitcher plants, cacti, and mesophyll tissues, developed a bioinspired Janus mesh based on sodium carboxymethyl cellulose‐Ca 2+ /palmitic acid. Through ionic cross‐linking and solvent‐induced crystallization processes, an asymmetric interface with a 138° wettability gradient is constructed. By synergizing capillary condensation and Laplace pressure differences, rapid directional transport of fog droplets within 0.07 s is achieved. The Janus mesh demonstrates fog collection efficiencies of 0.72 and 1.80 g cm −2 min −1 under vertical and 15° inclined conditions, respectively, which are 2.06 and 5.1 times those of the original stainless steel mesh. This research integrates high‐efficiency water collection with environmental friendliness, offering a new paradigm for arid regions, and its design concept can be extended to other domains.