Modification of wettability property of titanium by laser texturing

Three different microstructures with line pattern, grid pattern, and spot pattern were fabricated on titanium surfaces by nanosecond laser. Scanning electron microscopy (SEM), contact angle measurement, surface roughness gage, and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize and measure the surface morphology, contact angle, surface roughness, and chemical composition of titanium after laser processing. The results indicate that the contact angle of titanium surface is 77.8A degrees immediately after laser processing, which shows hydrophilicity, and the contact angle presents a rising tendency with time in general. At steady state, the maximum contact angles for line pattern, grid pattern, and spot pattern increased to 157.2A degrees, 153A degrees, and 132.5A degrees, respectively. It can be found that the surface wettability has changed from hydrophilicity to hydrophobicity and even to superhydrophobicity. The influence of surface morphology on the surface wettability effects immediately after laser treatment and does not change with time, while the effect of surface chemical composition on the surface wettability will continue from the beginning of laser processing to the stabilization of surface chemical composition. Finally, it can be deduced that the accumulation of carbon on the surface is probably the critical factor to improve the surface hydrophobicity. Therefore, it is concluded that laser-induced modification of surface wettability correlates with surface morphology and surface chemical composition.