Design,Preparation And Performance Of High Efficiency Bionic Water-collecting Coating

Plants and animals living in dryland have abilities to resist drought and to collect water.The desert beetle and cactus are two kinds of typical drought-resisting plants and animals.Leaves of cactus have evolved into spicules,and the surface of the stem has been covered with waxy tissue protecting against the drought and heat of the desert.There is a special hydrophilic-hydrophobic structure on desert beetle's back.Hydrophilic bumps are able to collect water in fog,while hydrophobic pits can quickly guide water away.Hence,a lot of bionics researches about these two organisms have been started.In this research,two key processes of condensation and droplet detachment were analyzed,and a waterproof water-collecting coating was designed and prepared for the purpose of low cost and widely application,and the water-collecting performance was analyzed and studied.The main conclusions as follows:In theoretical simulation,the simulation of thermal equilibrium shows that surface emissivity is of great help to reduce surface temperature and promote condensation of fog.In theory,0.85 emissivity material only can condense water droplets from air at 60% humidity.In the analysis of plant structure and water-collection effect,it is found that water is not the only factor that determines leaf emissivity.In the cactus structure,the micro-scale(approximately 3.6 um)structure enhances the scattering of mid-infrared band,which is one of the reasons for its high emissivity.The low cost and easy preparation of water-collecting coating of imitation beetle was studied.Using common palm wax emulsion as additive,the contact angle of coating reached 112±4°,and the water collection efficiency was improved by 53% compared with that of PET substrate.The water collecting efficiency about two ways of preparing hydrophobic coatings with hydrophilic structure was prepared and compared by sandpaper grinding and a new method of sieve-vibrating with powder-dusting.In addition,the coating was roughened to obtain sub-micron roughness,resulting in a 57.94% improvement in water collection efficiency compared with that of PET substrate.