Fog harvesting on micro-structured metal meshes: Effect of surface ageing

Access to clean drinking water is a critical need for human societies. Intercepting atmospheric fog can help collect water from the atmosphere, even in situations of high-water scarcity in fog-prone areas. Metal meshes or screens are commonly used as fog collectors, where the mesh surfaces are often engineered to enhance water collection rates. Despite significant work over the past several decades, the ideal surface wettability desired in terms of surface roughness and functionalization for efficient fog harvesting is not well understood. The volume of water collected depends on the proportion of fog intercepted by the meshes and how effectively the deposited water droplets drain off into the collector. In this work, we employ scalable surface treatments such as chemical etching and atmospheric pressure vapor deposition on stainless steel meshes to alter the surface wettability. We evaluate the efficacy of fog harvesting on the wettability altered meshes, and compare their performance against untreated stainless steel meshes. We further investigate the effect of surface ageing on the wettability and fog collection performance. Our work not only offers valuable design guidelines for the development of effective fog collectors but also highlights the significant influence of the atmosphere in controlling wetting behaviour.