We have introduced water-in-oil emulsion systems to generate confining geometries for the self-organization of monodisperse silica nanospheres as building block particles. Then, through the slow evaporation of emulsion phases by heating, these nanospheres were packed into structural colloids such as raspberry-shaped micro-particles. The suspension of colloidal clusters was deposited onto glass substrate followed by surface modification of fluorinecontaining silane coupling agent to produce superhydrophobic surface with dual scale roughness. Similar self-assembly approach was employed to fabricate macroporous micro-particles from composite micro-particles of polystyrene microspheres and antimony-doped tin oxide nanoparticles by calcination. After deposition of the porous particles and fluorine treatment with silane coupling agent, superhydrophobic surfaces which have potential applications such as self cleaning property could be obtained with contact angle of water larger than 150℃.
Frei RM, Contact angle investigations on substrates with controlled periodic roughness: different asperity sizes and different substrate temperatures, Semester Project, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland, 2004