Optically transparent superhydrophobic silica-based films

Optically transparent superhydrophobic silica-based films were obtained by means of sol–gel processing and self-assembly (SA). Desired surface roughness was obtained by tuning the microstructures of the sol–gels through careful control of hydrolysis and condensation reactions of various silica precursors during sol–gel processing, whereas modification of surface chemistry was done by introducing a monolayer through surface condensation reaction. Such coatings were obtained by dip-coating the silica sols directly onto substrates, followed with self-assembly. The resultant silica-based coatings showed optical transparency higher than 90%, and the reflection lower than 10%, and the best advancing and receding water contact angles were found to be of approximately 165j/115j. Such coatings can have applications where anti-reflection, optical transparency and superhydrophobicity are required, in addition to low temperature processing. In addition, such films can be made at room temperature involving no expensive equipment or tedious processing, and be readily coated on various substrates. D 2004 Elsevier B.V. All rights reserved.