Study On The Measurement Method Of The Interaction Between Water Droplets And Hydrophobic Surface In The Air

Super-hydrophobic phenomenon widely exists in nature and daily life.Its unique self-cleaning ability brings many conveniences to production and life,but its weak interaction with liquid also brings many troubles to industrial and agricultural production.Study on the contact process between the hydrophobic surface and water droplets is the key to rationally utilize the super-hydrophobic structure.To this end,this research is devoted to the study on the measurement method for interaction between water droplets and super-hydrophobic surfaces in an air environment,laying the foundation for the development of the superhydrophobic field.In this research,the importance of accurately measuring the interaction between water droplets and super-hydrophobic structures in air environment was analyzed first combining the positive and negative effects of super-hydrophobic structure on industrial production and daily life.The research plan of this topic was initially determined.Then a millimeter-scale micro-cantilever with rectangular structure was designed to meet the force detection requirements in the measurement of the interaction between water droplets and super-hydrophobic surface.A system for non-contact microcantilever stiffness measurement based on electrostatic force was designed,and stiffness measurement of the self-designed millimeter-scale microcantilever beam was completed.Then Super-hydrophobic surface using polydimethylsiloxane(PDMS)and copper grid was prepared by different methods.The morphology was observed and properties characterization was carried out.Finally,using millimeter-scale microcantilever and optical lever,a system for the measurement of interaction between water droplets and super-hydrophobic structure was designed.The principle of the system was deduced and the system was built based on the electrostatic force generation and the principle of optical lever.The optical lever force sensitivity(OLFS)was calibrated and the measurement experiments of interaction between water droplets and different wettability super-hydrophobic surfaces were carried out.According to the results,the stiffness of millimeter-scale micro-cantilever was measured as 0.322 N/m and the relative uncertainty was 3.24%,meeting the measurement requirements in the air.PDMS super-hydrophobic surface had a three-stage micro-nano structure and copper grid super-hydrophobic surface had a two-stage micro-nano structure.The contact angles of both them are greater than 150°,in line with the definition of super-hydrophobic.The OLFS of measurement system of the interaction between water droplets and hydrophobic surface was measured as 10.431μN/V.The contact forces between water droplets and hydrophobic surface were micro-newton scale,and the measured contact forces between water droplets and hydrophobic surface which are based on copper grids with 100 mesh,150 mesh and 300 mesh are 0.6027μN,0.4565μN and 0.3152μN.The contact forces are decreased with the increase of hydrophobic,in line with the energy theory.