Hybrid laser and vacuum process for rapid ultrahydrophobic Ti-6Al-4V surface formation

A novel technique of post-vacuum processing the laser patterned surface was used for high speed fabrication of Ultrahydrophobic Ti6Al4V surface and the basics behind the transformation of surface chemistry is investigated in this paper. The wetting property of the laser patterned dual geometry structures transforms to ultrahydrophobic in 120 min of vacuum process without any chemical treatments to suppress the surface polarity. The surface recorded static contact angle of 180 degrees, sliding angle less than 5, and exhibits bouncing and roll-off characteristic due to the presence of composite interface. The transformation of hydrophobic property establish a clear relationship between the vacuum process period and the improvement in static contact angle. The surface chemical analyses by XPS reveals that the amount of surface carbon content increases 2.3 times higher because of the adsorption of unstable organic molecules by vacuum process. The low partial pressure of the water molecules (120 min.) compared to those occurs at standard atmospheric pressure (days). The transformation of freshly laser processed Ti6Al4V hydrophilic surfaces into ultrahydrophobic surface is due to the development of carbonaceous layer over the laser patterned structures, which helps to sustain the Cassi-Baxter state.