Fog catcher brushes with environmental friendly slippery alumina micro-needle structured surface for efficient fog-harvesting

Water pollution has caused serious water shortage, and this trend becomes increasingly serious in the world. Therefore, how to efficiently access water resources is crucial for human beings. Considering the easy blockage problem of traditional fog-harvesting mesh, we used the fog catcher brushes structure to avoid the problem effectively. Besides, most of the modified coatings on fog-harvesting materials contain fluorosilane, which is expensive, harmful and unstable for a long time using. In addition to the general properties of dimethyl silicone oil, hydrogen methyl silicone oil can participate in a variety of chemical reactions and have a good film-forming performance due to its molecular structure containing active Si–H keys compared to the similar studies about the oil-infused coating. Besides, the low contact angle hysteresis of the droplet can benefit for the droplet sliding off the surface, which further improve the fog-harvesting efficiency. In this paper, mechanical cutting method, water bath method, and spray coating method were successfully combined to construct slippery “fog catcher brushes” with alumina micro-needle structured surfaces from micro control to macro design. Furthermore, the effect of wettability, pattern shape and pattern size on fog-harvesting performance were investigated. Experiment results indicated that slippery surface benefited for the fog deposition and transportation compared with the superhydrophilic and plain surface. When the fog droplets passed through the sample with 10-teeth arc-shaped pattern, it would fully contact the surface, and only a small amount of fog droplets escaped from the surface. With the adjacent droplets coalescing, the droplets slided off along both sides of the pattern, then the contact surface decreased gradually from the top to the bottom, so droplets could transport rapidly. Analysis demonstrated that the slippery arc-shaped fog catcher brushes with 10-teeth had a good effect on the capturing and transporting of fog droplets, which offered a way to rationally construct materials with enhanced fog-harvesting performance from micro control to macro design.