Fabrication of Cactus-Inspired Superwetting Meshes for Highly Efficient Fog Harvesting

Fog harvesting is a promising technique to obtain fresh water in arid climates. Through a combination of the template method and the photocuring technique, we effectively crafted cactus-inspired structures on a copper mesh to enhance the coalescence and transport of droplets. The spacing of the needle array can be readily customized by altering the quantity of holes in the photomask. Simultaneously, the wettability of both the mesh and the conical needles can be modified through a straightforward surface treatment. The cactus-inspired superwetting meshes could be used as an effective fog collector. Droplets on a superhydrophilic copper mesh with a superhydrophilic needle array (HICM-NA) can swiftly and directly migrate due to Laplace pressure induced by the shape gradient and capillary forces stemming from the groove structure on the needles. The depth of the groove progressively grows from the needle tip toward the root, leading to a gradual amplification of the capillary force on the droplet as it traverses the surface. In addition, HICM-NA adopts a mode of liquid film transmission, which can reduce the friction resistance during transportation. The water collection efficiency of HICM-NA is as high as 17.7 kg h(-1) m(-2). However, a superhydrophobic copper mesh with a hydrophilic needle array (HOCM-NA) has a high barrier between the mesh and the needle, suppressing the transport of droplets.