Hierarchically structured superhydrophobic coatings fabricated by successive Langmuir-Blodgett deposition of micro-/nano-sized particles and surface silanization

The present study demonstrates the creation of a stable, superhydrophobic surface by coupling of successive Langmuir-Blodgett (LB) depositions of micro-?and nano-sized (1.5?μm/50?nm, 1.0?μm/50?nm, and 0.5?μm/50?nm) silica particles on a glass substrate with the formation of a self-assembled monolayer of dodecyltrichlorosilane on the surface of the particulate film. Particulate films, in which one layer of 50?nm particles was deposited over one to five sublayers of larger micro-sized particles, with hierarchical surface roughness and superhydrophobicity, were successfully fabricated. Furthermore, the present 'two-scale' (micro-?and nano-sized particles) approach is superior to the previous 'one-scale' (micro-sized particles) approach in that both higher advancing contact angle and lower contact angle hysteresis can be realized. Experimental results revealed that the superhydrophobicity exhibited by as-fabricated particulate films with different sublayer particle diameters increases in the order of 0.5?μm>1.0?μm>1.5?μm. However, no clear trend between sublayer number and surface superhydrophobicity could be discerned. An explanation of superhydrophobicity based on the surface roughness introduced by two-scale particles is also proposed.