Study On The Wetting Behavior Of Droplets On The Surface Of Microporous Structure At Elevated Temperature

Nowadays,more and more scholars pay attention to the study of surface wettability.With the development of research,people can further improve the hydrophobicity of material surface by changing the influencing factors,which has a good application prospect in industry,military,daily life and so on.However,the wettability is affected by many factors,which need a lot of experimental data and theoretical to analysis the influence of different factors on wettability.This paper focuses on the study of the wettability of droplets from the perspective of microstructure parameters.In this paper,PDMS is selected as the material to fabricate the microporous surface with different microporous spacing,cross-section shape and depth.In the experiment,the silicon wafer is used as the substrate,and the array micro column structure surface is manufactured by photoetching and etching technology.Then the surface of microporous structure is made by nano imprinting.The two-dimensional and three-dimensional morphology of the surface microstructure was observed by optical microscope and laser scanning confocal microscope,and its size was characterized.After that,the static contact angles of PDMS microporous membrane were measured at room temperature and elevated temperature.Arranging the data and drawing the change line chart of contact angle,which based on the principle of single variable.Finally,the influence of droplet wettability was analyzed by the point of view of microporous structure parameters between micropore spacing,section shape and depth.According to the experimental results,microporous structure can improve the hydrophobicity of PDMS surface to a certain extent.In the process of heating up,the contact angle will decrease,but the wetting state will not change.The wettability of droplets is mainly affected by the micropore spacing.The change of spacing will directly cause the change of surface porosity and solid-liquid area fraction,and then the air cushion density will decreased in unit area.In addition,the surface tension decreases under the heating state.Laplace pressure and gas pressure change to break the original equilibrium state of the droplet,and then microporous grooves are further wetted.Thus we observe that the contact angle was decreased.Especially when the surface porosity drops to a certain value,the influence of the microporous cross-section shape and the microporous depth on the wettability of the droplets will be less obvious.