Various proposals exist in the art for the production of superhydrophobic coatings. See in this regard, Shang et al, “Nanostructured superhydrophobic Surfaces”, J. Mater. Sci. 40 (2005) 3587; Lau et al “Superhydrophobic Carbon Nanotube Forests”, Nano Letters, 3 (2003) 1701; Ren et al, “Preparation and Characterization of an Ultrahydrophobic Surface Based on a Stearic Acid Self-Assembled Monolayer over Polyethyleneimine thin Films”, Surface Science, 546 (2003) 64; Mock et al, “Towards Ultrahydrophobic Surfaces: A Biomimetic Approach”, J. Phys.: Condens. Matter 17 (2005) S639; and Fresnais et al, “Polyethylene Ultrahydrophobic Surface: Synthesis and Original Properties” Eur. Phys. J. Appl. Phys. 26 (2004) 209, the entire content of each such prior publication being expressly incorporated hereinto by reference.
While superhydrophobic properties may in fact be achieved by the techniques disclosed in the prior publications identified above, they are typically limited by substrate size (i.e., are not suitable for coating onto a large substrate area), are time consuming and/or are not sufficiently robust for surface finishes. For example, the production of nanofibers by electrospinning cannot be used in a paint or coating application and is limited to relatively small substrates. Nanotubes produced on a surface by vapor deposition (or other methods) are limited to small substrates; require high temperature substrates and cannot be used in a coating. Self-assembled multilayers are likewise limited in substrate size and are impractical commercially due to their time consuming (e.g., several days) to produce a suitable structure. Photolithographic processes are not applicable as coating as they are limited in substrate size and require high temperature substrate. Plasma treatment process are not applicable as a coating; are limited in substrate size and are cost-prohibitive to use on a meaningful commercial scale.
Recently, the superhydrophobic behavior of the lotus leaf structure has been mimicked by providing a honeycomb-like polyelectrolyte multilayer surface with silica nanoparticles and then coating such highly textured surface with a semifluorinated silane. See, Zhai et al, “Stable Superhydrophobic Coatings from Polyelectrolyte Multilayers”, Nano Letters 4 (2004) 1349-1353, the entire content of which is expressly incorporated hereinto by reference.