Enhanced fog harvesting through programmable droplet movement via bidirectional wettable gradient and microchannel-connected pattern gradient

Significant efforts have been devoted to overcoming the capture efficiency decline and mesh clogging, known as the main problems of current mesh-type fog harvesting surface. In this study, a novel integrative bioinspired Janus mesh with bidirectional wettable gradient and microchannel-connected pattern gradient (BWMPG) is proposed to deal with the chronic problems via a novel anodic oxidation strategy. Peculiar fog harvesting behaviors were programmed, i.e., fog capture and transport processes occur simultaneously on separate surfaces. Such a surface could not only provide benefits for fog capture owing to spontaneous penetration of collected droplets but also expedite droplet transport by taking full advantage of the cooperation of multiple driving forces. More importantly, it also exhibits an excellent surface regeneration rate via the connectivity of the microchannels to accelerate the coalescence frequency of droplets on different hydrophilic points. The results of experiment observation and underlying mechanism analysis have certified that such a design is more conducive to enhancing the fog harvesting efficiency (0.48 g/cm²·h), resulting in a 320 % increase compared to the normal hydrophilic−hydrophobic patterned surface.