Time dependency of superhydrophilic and superhydrophobic surfaces produced by nanosecond laser irradiation assisted by post-annealing and silanization

Abstract

Modifying implant surfaces to be superhydrophilic or superhydrophobic is a promising approach to improve their biocompatibility. In this paper, nanosecond laser irradiation assisted by post-annealing and silanization was employed to control the wettability of Ti6Al4V surfaces. Through adjusting the scanning interval (h) and speed (v), smooth surfaces with gradient hydrophilicity were achieved by laser gentle ablation, and superhydrophilic surfaces with gradient roughness were achieved by laser strong ablation. Assisted by subsequent post-annealing treatment or silanization, various superhydrophobic surfaces were produced within only several hours. The wettability stability of these superhydrophilic and superhydrophobic surfaces in the atmosphere and different liquid solutions was evaluated, and the related mechanism was discussed in detail. Finally, long-term superhydrophilic surfaces in both atmosphere and normal saline were obtained by applying small v and h values. Meanwhile, various long-term (in the atmosphere) superhydrophobic surfaces in a metastable state (like a rose leaf) were obtained via post-annealing treatment, and those in a Cassie state (like a lotus leaf) were produced by silanization. The results in this paper could also be applied in several potential applications such as self-cleaning, micro-fluidic chips, and micro-operation of droplets.