Stable and Transparent Superhydrophobic Nanoparticle Films

A superhydrophobic surface with a static water contact angle (theta(w)) > 150 degrees was created by a simple dip-coating method of 60-nm SiO2 nanoparticles onto an amine-terminated (NH2) self-assembled monolayer (SAM) glass/silicon oxide substrate, followed by chemical vapor deposition of a fluorinated adsorbate. For comparison, a close-packed nanoparticle film, formed by convective assembly, gave theta(w) similar to 120 degrees. The stability of the superhydrophobic coating was enhanced by sintering of the nanoparticles in an O-2 environment at high temperature (1100 degrees C). A sliding angle of < 5 degrees indicated the self-cleaning properties of the surface. The dip-coating method can be applied to glass substrates to prepare surfaces that are superhydrophobic and transparent.