A biomimetic hierarchical structure on selective laser melting titanium with enhanced hydrophilic/hydrophobic surface

A novel approach was developed to construct a hierarchical micro- and nano-structure on selective laser melted (SLM) titanium surface. The process-inherent roughness of SLM-Ti was used as the template for assembling TiO₂ nanotube arrays (NTAs) to obtain a series of the micro-/nano- topographies in one step. The results show that TiO₂ NTAs on SLM-Ti without ultraviolet irradiation and annealing treatment exhibits superhydrophilic characteristic. The complete wetting is due to the spread of water droplets inside the spherical particles on SLM-Ti surface. Fluorinated TiO₂ NTAs on SLM-Ti exhibits superhydrophobic characteristic. Water droplets move spontaneously on the horizontal surface with almost no contact angle hysteresis. More importantly, the water contact angle and contact angle hysteresis can be controlled by the fine design of the SLM-Ti anodization process. The process-inherent surface roughness of SLM-Ti seems to present a significant potential for the development of superwetting materials, which can fulfill various technological demands.