Incollection,
Polymer and nanoparticle based superhydrophobic surfaces: supports for optical microcavities of liquid microdroplets
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)
Abstract
Surface hydrophobicity is enhanced by roughness. While the contact angle of a water droplet can be maximum ~120o on a smooth hydrophobic surface, it can be increased above 150o by surface roughness. Applications of superhydrophobic surfaces require control of the surface roughness from micrometer to nanometer length scales. Nano-rough surfaces are transparent to visible light and have potential to be used in optical applications. This talk will focus on controlling the roughness of polymer and nanoparticle based surfaces at different length scales and the use of water microdroplets on nano-rough superhydrophobic surfaces as tunable optical microcavities. Control of roughness length scales and surface hydrophobicity of coatings prepared by the following four material systems will be discussed: i) a semi-crystalline homopolymer: isotactic polypropylene; ii) a nanocomposite: silica nanoparticles in polystyrene; iii) block copolymers; iv) surface coated nanoparticles. On superhydrophobic surfaces, water microdroplets act as optical microsphere microcavities due to their nearly spherical shapes. Transparency of the surfaces to visible light allows the optical characterization of the microcavities. In a humidity chamber, we have demonstrated the tunability of these microcavities over large spectral ranges by controlled evaporation and condensation. The importance of tunable optical resonances from water microdroplets will be discussed.
