Preparation Of Mechanically Durable Superhydrophobic And Superoleophobic Materials And Their Application

Examples of superhydrophobic surfaces found in nature such as selfcleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades.When a water droplet rests on a textured surface,it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry.Super water-repellent surfaces have numerous applications in our daily life such as drag reduction,anti-icing,antifogging,energy conservation,noise reduction,and self-cleaning.In fact,the same concept could be applied in designing and producing surfaces that repel organic contaminations(e.g.low surface tension liquids).However,superoleophobic surfaces are more challenging to fabricate than superhydrophobic surfaces since the combination of multiscale roughness with re-entrant or overhang structure and surface chemistry must be provided.In this study,simple,cost-effective and potentially scalable techniques,i.e.,airbrush and electrospray,were employed for the sake of making superhydrophobic and superoleophobic coatings with random and patterned multiscale surface roughness.Different types of silicon dioxide were utilized in this work in order to study and to characterize the effect of surface morphology and surface roughness on surface wettability.The experimental findings indicated that super liquid repellent surfaces with high apparent contact angles and extremely low sliding angles were successfully fabricated by combining re-entrant structure,multiscale surface roughness,and low surface energy obtained from chemically treating the fabricated surfaces.Having the hierarchical structure is essential for high durability and strength of the fabricated surface.The re-entrant structure was formed by performing metal etching before actually painting the substrate with the manufactured solution.The cylindrical structure formed by metal etching is basis of the durability of mechanical structure of nano surface painted afterwards.After metal etching,Silicon dioxide(Si O2)and perfluorodecyltrichlorosilane(FOTS)with ethanol solution was prepared.The substrate was cleaned with toluene and dried beforehand.The substrate was first dip coated and dried in oven.Finally,to increase the durability of surface structure,Polydimethylsiloxane(PDMS)was used during dip coating and spray coating to increase the durability of fabricated structure.