Research On Influencing Factors Of Wettability Based On Contact Line Theory

The discovery of superhydrophobic phenomena in nature has promoted the development of wetting theory and attracted many researchers to explore the wetting mechanisms.Extremely wetted surfaces such as super-hydrophilic or super-hydrophobic surfaces have demonstrated significant value in application of both domestic and industrial production.Super-hydrophobic surface can be used for anti-icing of the aircraft front,drag reduction of submarines,micro fluid delivery,anti-snow-coverd of wire,waterproof clothes.Similary,super-hydrophilic surfaces also shows its excellent characteristics in the lubrication of the medical catheter,glass surface self-cleaning,biological antibacterial,etc.The researchers looked at the surface of plants and animals and found that the surface microstructure and surface free energy were the two main factors affecting the wettability.Researchers consider that the surface microstructure and surface free energy are two major factors that affect wettability by observing the surface of animals and plants.This led to the emergence of Wenzel and Cassie's two classic theoretical models which is still used to guide the research and preparation of wettable surface today.Although there is a lot of research nowadays on wettability,it mainly focuses on the exploration of the preparation process and production application.However,there is less research on wetting mechanism and a complete theoretical system has not yet been formed.The investigation of wettability theory is the basis for guiding actual production and processing.Analyzing the influencing factors of wettability can help people better understand the mechanism of wetting,reasonably formulate the processing technology,and obtain the required functional surface.In order to explore the main factors affecting the wettability,the contact angle is used as an indicator to measure the degree of wetting,and according to the concept of the contact line density proposed by Extrand,a mathematical model for solid-liquid contact equilibri?m is established at the contact line.The wettability changes of trenches and square col?mns under different influencing factors were analyzed combining with experiment on PTFE and copper surface.The specific work is as follows:(1)In combination with the contact line theory of Extrand,this paper analyzes the equilibrip?m states on the contact line on hydrophilic and hydrophobic,grooves and square col?mns surface.By comparing the droplet hydrostatic pressure and the additional pressure at the contact line could judge the wetting state.The influence of the contact line density,the density of the measured solution,the volp?me of the drop,and the the surface energy of solid on the wettability were respectively predicted.(2)Formulate the micro-structure size parameters and processing technology plan.The groove structure was processed on the surface of copper and PTFE,respectively,to explore the effects of different rotation speeds,different feed rates,and different depths of cut on the surface burr generation,to find the most reasonable processing parameters,and apply to the subsequent microstructure processing.(3)Preparation of trench and square pillar microstructures on different surfaces of PTFE and copper,and electrolytic treatment of the processed burrs.Photographing the morphology of the samples and measuring the contact angle under deionized water and different concentrations of NaCl solution on drop analyzer.(4)The contact angle measurement results are calculated and analyzed according to the theoretical formula of the contact line.Combined with the theoretically predicted wetting behavior,the influence of the contact line density,the measured solution density,the measured drop vol?me,and the surface energy of the solid on wettability are respectively explained.