Synthesis of superhydrophobic SiO2 layers via combination of surface roughness and fluorination

We describe the preparation of superhydrophobic SiO2 layers through a combination of surface roughness and fluorination. Electrospraying SiO2 precursor solutions that were prepared by a sol–gel route and included trichloro(1H,1H,2H,2H-perfluorooctyl)silane as a fluorination source produced highly rough, fluorinated SiO2 layers. In sharp contrast to the fluorinated flat SiO2 layer, the fluorinated rough SiO2 layer showed much enhanced repellency toward liquid droplets of different surface tensions. The surface fraction and the work of adhesion of the superhydrophobic SiO2 layers were determined, respectively, based on Cassie–Baxter and Young–Dupre equations. The satisfactory long-term stability for 30 days, the ultraviolet resistance and the thermal stability up to 400oC of the superhydrophobic SiO2 layers prepared in this work confirm a promising practical application. A schematic illustration of the electrospray deposition used for preparing SiO2 layers. Shapes of liquid droplets of water, glycerol, coffee, juice and milk created on the fluorinated rough SiO2 layer deposited on a silicon wafer. [Display omitted] ► Superhydrophobic SiO2 layers are realized by a combination of surface roughness and fluorination. ► The fluorinated rough SiO2 layer shows enhanced repellency toward various liquid droplets. ► The wetting behavior is explained based on Cassie–Baxter and Young–Dupre equations. ► The superhydrophobic SiO2 layers confirm a promising practical application.