Construction Of Bionic Hybrid Wetting Surface And Its Condensation Characteristics

Gas-liquid phase condensation is a common phenomenon in the process of mass and heat transfer in nature.In recent years,the reasonable control of gas-liquid phase change behavior?such as dropwise condensation of water vapor?has been a popular topic in the fields of water collection,heat transfer and desalination.In practical engineering application,gas-liquid phase transformation is needed to realize rapid condensation and timely departure from the material surface.Superhydrophobic surface could achieve the aim of droplets removed rapidly,but it is difficult to meet the requirement of rapid condensation because of its high nucleation barrier and the surface condensation behavior is suppressed.On the other hand,hydrophilic/superhydrophilic surface with high nucleation rate and large amount of dewdrop,but the great surface adhesion lead to the formation of"water film"on the surface,which result to that the water is difficult to be removed.Therefore,how to ensure efficient condensation and rapid departure from is one of the urgent issues in the field of related applications.In this paper,a patterned hybrid wetting surface with hydrophilic/hydrophobic wedge-shaped silica pillar arrays?hydrophilic/hydrophobic on the top of the pillar,and superhydrophobic on the rest of the surface?were constructed inspired by the condensation and water collection behavior of desert beetles,cactus and other organisms.The design of wedge-shaped hydrophilic/hydrophobic pillar arrays not only enhance the nucleation and condensation effect on the material surface,but also promote the transport of drops by Laplace pressure gradient on the wedge-shaped surface.The strengthening mechanism of condensation,dynamic transportation and directional removal mechanism of water droplets on the wedge-shaped patterned hybri wettability surface were studied,and the corresponding mathematical models were established.In the condensation test,the condensation amount and removal amount generated by the patterned hybrid wetting surface were much higher than that of the uniform superhydrophobic coating,and the water collection rate as high as 11862.2g/m²/h could be obtained in the water collection test,which equivalent to 11 times of the homogeneous superhydrophobic coating.Inspired by the water collection structure on the back of the desert beetle,the composite coating of TiO₂-SiO₂ was prepared by maskless photocatalytic technology.In combination with the photocatalytic principle of TiO₂,the method of ultraviolet exposure was adopted to promote the catalytic decomposition of fluorosilane monolayer on the surface of TiO₂ in the superhydrophobic composite coating,so as to obtain the hybrid wetting coating with hydrophilic TiO₂ and superhydrophobic SiO₂ nanoparticles.Owe to the presence of hydrophilic TiO₂ nanoparticles,they enhanced the surface nucleation and condensation efficiency,and the surface energy released by the coalesced drops could cause self-drive jump phenomenon.Therefore,the optimized hybrid wetting composite coating not only has higher nucleation and condensation efficiency,but also with higher dew-drop removal efficiency.The results above show that the optimized coating surface can obtain water collection rate up to 1742.9 g/m²/h,which is equivalent to about 2 times of TiO₂-SiO₂ superhydrophobic coatingand 5 times of hydrophilic aluminum sheet surface,respectively,and it plays a better role in enhancing water collection.Based on the principle of molecular dynamics,hydrophilic polymers were modified on the surface of ceramic particles,and a hybrid wetting coating with superamphiphobic properties?superoleophobic and superhydrophobic?was prepared by means of hybrid adjust and control with hydrophilic particles.Further study results show that when the hybrid wetting coating regulated by SiC@PAA particles,the surface nucleation efficiency could be enhanced due to the large amount of hydroxyl groups on the hybrid wetting surface.The amount of condensation and removed droplets were significantly higher than that of homogeneous superamphiphobic coating,and the water collection rate was up to 2742.7g/m²/h,which equivalent to about 2.6 times of homogeneous superamphiphobic coating.Further tests showed that the hybrid wetting coating also had better oil/water self-cleaning effect and defrost removal effect,which solved the problem of poor anti-fouling ability of water collection surface effectively,and it provided technical support and theoretical basis for the construction of efficient water collection surface with low cost,simple process,strong anti-fouling ability,better defrosting remove efficiency and conducive to large-scale production.Hybrid wetting fibre was prepared by coating modified method.It was found that the water collection rate of the hybrid wetting fibre could reach about 1.77×10⁵ g/m²/h,which was about 4.7 times of that of the superamphiphobic fiber.Further study found that,water droplets on the hybrid wetting fiber not only could realize gravity stripping and jump stripping,but large water drop stripping could also cause the fiber vibration,and the water droplets could be removed under the influence of such factors as inertial effect and fiber rebound effect,which improved the removal efficiency and water collection efficiency on the surface of the fiber effectively.