Superhydrophobic silica films on glass formed by hydrolysis of an acidic aerosol of tetraethylorthosilicate

Abstract

Silica microparticle films were deposited using a new hybrid chemical vapour deposition process. The combination of gaseous tetraethylorthosilicate (TEOS) and an acidic aerosol resulted in the acid catalysis of TEOS, this produced silica microparticles which then deposited onto a glass substrate to form a continuous film. The microparticle films as formed were exceptionally rough and superhydrophilic, with water contact angles below 5°. The size of microparticles in the films could be controlled by varying the temperature at which they were deposited. The surface silanol groups of the hydrophilic films could then be functionalised using hexamethyldisilazane to form trimethylsiloxane groups. The resultant surface showed extreme hydrophobicity with water contact angles approaching 180° and a contact angle hysteresis near to zero. The functionalised silica films also demonstrated an elastic bounce of water droplets dropped onto the surface.