Coprecursor approach to the fabrication of superhydrophobic durable self-cleaning films

This paper presents a novel method to prepare inorganic superhydrophobic silica coatings for microelectro-mechanical systems (MEMS) packaging using sol-gel processing with tetramethoxysilane and isobutyl-trimethoxysilane as precursors. Incorporation of isobutyl-trimethoxysilane into silica causes hydrophobic isobutyl groups to be present on the surface, thus generating surface hydrophobicity. The particle size and porosity and therefore the surface structure can be controlled by pH, solvent evaporation rate, and precursor ratio. Goniometer measurements of silica films on glass slides indicated that these films displayed a contact angle of 170deg. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the surface morphology and structure and the results discussed with respect to the effect of surface roughness on superhydrophobicity. Electron dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA) were conducted to characterize the silica film composition. Improved UV stability was achieved compared to organic polymers such as fluorinated polybutadiene. FTIR was used to investigate the long term degradation of the superhydrophobic silica surfaces