Azobenzene multilayers were fabricated on silicon substrates by electrostatic self-assembly technology. Rough silicon substrates were prepared by photolithography and the inductive coupling plasma deep etching technique. Surface morphology and properties of azobenzene multilayer on the silicon substrate were characterized by SEM, UV-Vis spectra and contact angle(CA) measurement. Superhydrophobicity(CA is larger than 150°) on the multilayer was obtained by introducing geometrical structure onto the substrate surface. For the flat silicon substrate, CA on 10 bilayers was 83.4°±2.1°. For the rough substrate, CA was 150.9°±1.7°. After UV irradiation the CA decreased. A large reversible CA change about 37° was realized through ultraviolet and visible irradiation on the rough azobenzene film, comparing with that about 5° on the flat film. These results indicate that the surface roughness plays an important role in tuning surface wettability. Moreover, the reversible switching by photo-irradiation could be realized many times, and a good reversibility of surface wettability was observed.
