Study On The Wettability Transformation And Application Of Superwetting Surface Based On Light-modification

Since the discovery of the classical“lotus effect”,different types of superwetting surfaces have received significant attention and extensive discussion due to its advantages of low cost,high efficiency,and recyclability.Through adjusting the topography and chemical composition,the surface can perform completely opposite wettability to water and oil at the same time.The fabrication of superwetting materials could be used to deal with different oil/water mixtures,which has significant application value in environment protection and resources recovery.With the further research on the superwetting surfaces,the surface with wettability transformation has gradually attracted widespread attention,which the could be achieved by external stimulation,such as light,p H,electric potential,temperature,etc,due to the changes of surface topography and chemical composition.In recent years,the effect of surface topography on wettability has received extensive research.However,there are few theoretical studies about the influence of the surface chemical composition changes on surface wettability of the will cause the change of the surface tension,which would greatly affect the wettability of the surface,and the current researches on the wettability transformation surfaces have the problems of a narrow wettability switching range and a long wettability switching time.In addition,most studies of the wettability transformation mainly focus on the transformation of a single liquid（water or oil）rather than the multiple liquid wettability transformation（water and oil）,which limits the application of the surface.Aiming on the theoretical and application problems in the current researches on the wettability transformation surfaces,the relationship formula between surface wettability and surface tension has been derived,including the polarity component and the dispersion component,according to the classic Young’s equation and the adhesion work theory of interface interaction.Based on this,the dipolar groups or dispersive groups could be adjusted to change the surface tension according to the light-modificaiton mechanism of high surface energy inorganic oxides and low surface energy organics.And then,the relationship derived equation is used to quantitatively analyze the influence of surface tension changes of inorganic oxides and low surface energy fluorides on surface wettability.Finally,the theoretical model of surface tension and wettability based on light modification is summarized and established.A superoleophobic/superhydrophilic coating is fabricated via modifying the TiO₂ particles obtained by liquid-phase deposition with perfluorooctanoic acid.The influence of the change of suface tension on surface wettability after passive changes in surface chemical composition（failure caused by long-term immersion in water）has been investigated,as well as the mechanism of wettability transformation.The wettability of the coating could transform to suphydrophobic/superoleophilic,and the wettability stability of the coated surface in acid,alkali and salt solution environments and the oil/water separation performance before and after wettability transformation have been explored.The efficiency of these oil/water separation is all over 99%.The deposited titanium dioxide particles on the fabricated surface in this paper can effectively remove the fluoride attached to the particles through photo-decomposition for reducing the emission of harmful fluoride to the environment.Based on the mechanism anasysis in Chapter 2,the superhydrophobic surface is prepared by modifying TiO₂ or Al₂O₃ particles with fluorides.The surface chemical composition was actively adjusted by ultraviolet light to change the surface tension,and then the surface wettability could be controlled.The common points and differences of wettability transformation of these two surfaces has been explored.And the effects of the concentration of the modified fluoride and the length of its carbon chain on the rate and the cycle number of wettability transformation is also discussed.In addition,the transformation time from superhydrophobicity to superhydrophilicity has been significantly shorten.The rapid wettability transformation provides a solution for the separation of multi-component oil/water mixtures.Based on the mechanism anasysis in Chapter 2 and for practical applications,aluminum oxide micro-nanoparticles with different sizes are prepared to be stably superhydrophilic particle layers.The wettability of aluminum oxide before and after photo-modifying has been studied,and the oil/water separation device were designed to achieve the emulsion separation with different separation mechanisms.And the effect of the particle layer thickness on the separation performance is also investigated.In addition,the chemical self-assembly method has been used to modify the low surface energy fluoride on the transparent substrate.Base on the mechanism of light-responsive wettability,the dispersion component on the surface has been replaced by the polarity component with the light-modification method to make the surface superhydrophilic.The changes of surface chemical composition and the wettability in the process of photo-modification were explored,as well as the light transmittance,chemical durability and anti-fog ability of the motified surface.In summary,this paper combined theoretical analysis and experimental research to deal with theoretical and application problems in the current researches on the wettability transformation surface.The influence of surface tension changes on wettability was studied through adjusting the chemical composition of the surface with UV treatment,which provided theoretical basis for the wettability transformaton of superwetting surfaces.According to the established theoretical model,the wettability of two-phase（water and oil）transformation from superoleophobicity/superhydrophilicity to superhydrophobicity/superoleophilicity and the one-phase（water）reciprocating transformation between superhydrophobicity and superhydrophilicity are achieved.For practical applications,the light-modified superhydrophilic particle layer was prepared for emulsion separation and transparent,high chemical durability suprhydrophilic surface were prepared for optical equipment underwater environment.It provides corresponding preparation schemes for the multi-functionalization of superwetting surfaces.