Effect of UV laser treatment on wetting properties of TiNi alloy

The surface laser treatment of TiNi alloy by a Nd:YAG laser operating at a wavelength of 266 nm with different parameters (laser fluence 0.05–0.1 J/cm², number of laser pulses 600-6000) is presented. Different analyses, including the study of surface morphology, free energy, roughness changes, phase composition, and surface chemistry are evaluated in relation to the wettability control of TiNi alloy. The results reveal a remarkable enhancement in hydrophilicity, evidenced by a sharp decrease in the water contact angle from 75.0 ± 5.1° to 11.4 ± 5.1°. This wettability improvement is positively correlated with the increased laser fluence and the number of laser pulses. The main contribution to the wettability alterations after laser treatment belongs to the surface saturation with oxygen and a subsequent formation of an oxide layer. This oxide layer significantly increases the polar component of the surface energy, thereby enhancing the hydrophilic properties of the TiNi alloy.