Regulation Of Nanostructures And Fluid Transport On Anisotropic Bionic Surfaces

There are a lot of materials that work in special environment have highly requirements for self-cleaning,anti-icing,corrosion resistance and drag reduction performances.In nature,the surfaces of many organisms are also in constant contact with fluid,their special surface structures give them a unique surface fluid motion state.In recent years,the study of biomimetic anisotropic structure plays a positive role in improving the fluid wettability and motion state of material surface.Anisotropic structures face many difficulties and challenges in application,for example,the structure has low tunability,and the droplet has a single movement direction and state on the surface.The anisotropic structure surface also lacks the special fluid wettability,the droplet and the fluid movement lack the dynamics on the structure.Based on that,this work focuses on the study of three-dimensional anisotropic structure with adjustable structure,and a layer of micro-nano structure is grown on its surface to form a secondary structure.Through the regulation of micro-nano structure,the surface can obtain special wetting property.By regulating the anisotropic structure,the fluid can obtain special motion state and transport performance on the surface.At the same time,the two-dimensional anisotropy structure is also studied,and two kinds of wetting properties are realized on one sample by adjusting its surface.The main results are as follows:By hydrothermal method,ZnO micro-nano structure is prepared on the inner wall of silicone pipe,and the inner wall surface is superhydrophobic through fluorination process.The motion state of fluid in pipe is studied through experiment and Lattice Boltzmann simulation,the solid/liquid contact area of the fluid in the superhydrophobic pipe is small,which is conducive to reducing the fluid resistance.Experimental results show that the resistance of the fluid in the superhydrophobic pipe is less than that of the ordinary silicone pipe.When the liquid with a certain initial temperature is transported,the fluid temperature in the superhydrophobic pipe is always 1.5?higher than the ordinary pipe through the observation of infrared camera,which has better thermal insulation performance.Through the test of micron mechanical probe,the shape variable of a single ZnO structure is 3?m,and the maximum stress is 275?N.At the same time,the shear force of high-speed flow impacting the section of pipeline in the experiment is 193.6?N,the ZnO structure has good toughness and can fully withstand the impact of water flow.In the subsequent experiments,the pipe transports high-speed water flow,acid-base water flow,oil-water mixture and other liquids for a long time,and its internal hydrophobicity is stable.Biomimetic fin anisotropy structure is prepared by the soft complex method,and ZnO micro-nano structure is prepared on the fin structure by hydrothermal method.When the droplets impinge on the surface of the structure,they bounce off in a specific direction.By changing the shape of the fin structure,the droplets bounce off in a different direction,thus achieving the regulation of droplet driving effect.In addition,it is proved that the bionic fin structure with hydrophobic structure also has good drag reduction performance.The experimental ships sail under the tension of 10-100m N,and the average speed of ship with fin structure attached to the bottom is 1.5-4 times that of ordinary ship.The ZnO micro-nano structure on the surface of the anisotropic conical structure is prepared by hydrothermal and soft complex method.The composite structure is treated with fluorination and paint to have two kinds of wetting properties.The tip of the structure is hydrophilic and the root is hydrophobic.The conical structure is placed in the fog environment,and the hydrophilic tip is easy for droplets to condense,while the hydrophobic root is conducive to the timely release of droplets from the surface,so that the surface can obtain efficient fog collection performance.The length,spacing and proportion of hydrophilic part of the structure all affect its fog collection performance.The results of experiment and calculation show that the fog collection efficiency of the structure is best when the structure length is 4.2mm,the spacing is 1.5mm and the hydrophilic part accounts for 70%.TiO₂ micro-nano structure is prepared on glass sheet by coating and heat treatment.The superhydrophobic property of the structure is obtained by fluorination treatment.TiO₂ has the capability of responding to ultraviolet light.With the guidance of special photomask,the ultraviolet ray can selectively illuminate the surface of TiO₂,so that the surface has both hydrophilic and hydrophobic areas.By adjusting the shape of the photomask,the adjustable anisotropic hydrophilic-hydrophobic two-dimensional pattern can be obtained on the surface of TiO₂.When the fluid enters the pattern,it shows the effect of unidirectional transmission.Through experimental tests and Fluent ANSYS simulation,it is proved that linear and curved patterns have advantages in unidirectional transmission.For the linear structure,when the angle between the structure and the horizontal direction is 20°,the unidirectional transmission performance is the best,and the transmission distance is 234mm.For the curved structure,when the curvature radius of the structure is 10mm,the unidirectional transmission performance is the best,and the transmission distance is 276mm.Therefore,through the comprehensive regulation of three-dimensional and two-dimensional anisotropic surface with their micro-nano structure,makes their surfaces obtain special wetting and fluid transport performance,which plays a positive role in improving the self-cleaning,drag reduction and fluid transport performance of the material surface.