Efficient Fog-Harvesting\nOrigami Fan

Fog harvesting represents a promising strategy to address\nthe global\nfreshwater shortage. To enhance the water collection efficiency, diverse\ngeometric structures that can effectively drive water droplet movement\nare essential. Inspired by the Livistona chinensis leaf, which naturally facilitates directional droplet motion through\nits unique gradually varying V-groove structure, we have developed\na novel origami fan structure for fog harvesting through theoretical\nanalysis. A key feature is that we can modulate the speed of droplet\ntransport by adjusting the opening angle of the V-shaped grooves positioned\nat the outer circumference. Interestingly, the water collection efficiency\nexhibits a linear correlation with the opening angle. The highest\nefficiency of the origami fan can reach 5.75 times that of the control\ngroup calculated by the projected area and 3.76 times that of the\ncontrol group calculated by the real area, showcasing its significant\npotential for enhancing water collection from fog. The simulations\ndemonstrate that the hollow structure enhances the condensation rate\nof droplets, the geometric gradient of the gradual-variation V-groove\ndrives the condensed droplets to move rapidly on the surface, and\nthe Janus membrane permits the aggregated droplets to transit to the\nfan’s rear side. The synergistic action of these three components\nensures a clean surface for the subsequent water-collecting cycle,\ncontributing to the high fog-harvesting efficiency. Given its simple\nfabrication and superior water transfer efficiency, the origami fan\nholds substantial promise for widespread application in the field\nof droplet manipulation.