Wetting Properties Modification of TiO2 Layer by Femtosecond UV Pulses

In present work we have used femtosecond laser pulses to create different surface morphologies of titanium dioxide (TiO 2 ). TiO 2 layers were prepared from commercially available paste 13 nm, Tinano-oxide on glass substrates. Third harmonics ( = 343 nm) of femtosecond Yb:KGW laser (pulse duration = 300 fs) have been used to create TiO 2 surfaces (4x4 mm) of different morphology. Controllable pulse density was set to 2000 pulses per mm of length in X and Y axis. Beam diameter at 1/e 2 was 3,2 mm. F=75 mm plano-convex focusing lens have been used. Pulse energy has been varied from 0,02 J to 0,17 J to create different surface morphology. The surfaces have been characterized using optical microscope, profiler and scanning electrons microscope (SEM). Wetting characteristics where measured directly measuring static contact angle between layers surface and surface of distilled water droplet using CMOS camera. Contact angle was measured during 60 seconds after placing droplet on TiO 2 surface, because layer is nano-porous and part of water is being absorbed. The time-dependent changes of wetting angle at specified experimental conditions were video recorded. The volume of water droplet was controlled by microliter pipette (V~0,5L).