The Study Of Water Collection And Biomimetic Preparation About Pine Needle Surface

Obtaining inspiration from nature and preparing artificial water collection devices by imitating the surface structure of organisms have great application prospects and are of great significance to alleviate water shortages.In order to analyze the water collection mechanism and prepare a water collection structure with high water collection efficiency,the surface morphology,wettability and water collection performance of pine needles were studied.The results show that the pine needle semi-conical structure forms a unique shape gradient.The composite structure composed of grooves and pits on the surface of pine needles forms a wetting gradient.Laplacian pressure and surface tension gradients produced by shape gradients and wetting gradients enable the movement of water droplets on its surface.In order to explore the influence of surface material composition,surface microstructure and conicity on the surface water-collecting capacity,chemical corrosion,laser etching,and micro-cutting techniques were used,and brass was used as the substrate to construct surfaces with different material compositions,structures,and shapes.The test found that the sodium hydroxide and ammonium persulfate mixed solution corroded the hydrophilic copper hydroxide film formed on the surface of the brass,which made the surface of the test specimen change from hydrophobic to hydrophilic.By controlling the corrosion time,surfaces with different wettability can be constructed.The longer the corrosion time,the stronger the surface wettability,the easier it is to catch water droplets on the surface,and the higher the water collection rate.By laser etching,groove structures of different sizes can be constructed on the brass surface.As the laser power increases,the groove width also gradually increases,and the contact angle between the water droplet and its surface also increases.When the laser power is 12 W and the contact angle of the groove surface is 113.8°,it has a high water collection rate due to its strong ability to capture droplets and proper surface adhesion.When the water collection test is performed on the surface of the cone structure,the shape curvature of the cone is the main driving force of the droplet movement.Due to the influence of gravity and the existence of adhesion resistance on the surface of the cone,the speed and distance of the droplet movement vary with the change of the taper.When the taper is 6°,the water droplet moves at the fastest speed on the surface of the cone.In order to achieve efficient directional collection of water droplets,the influence of wetting gradient and shape gradient on the water collection performance of the bionic structure surface was explored.It was found that the three bionic structures showed similar water collection processes.When it is placed at 45° or 90°,due to the effect of gravity,the water droplets will move from the tip to the root under the effect of Laplace pressure and surface tension,and then drop from the surface under the effect of gravity.When the bionicstructure is placed at 0°,gravity has a small effect on the droplets condensed on its surface.Under the action of Laplace pressure and surface wettability gradient,the water droplet can move from the tip to the root end.When the taper is 6°,water droplets move fastest on the surface.Laser-etched and surface-gradient-etched bionic structures have the fastest water droplet transport speed.