Abstract
Laser irradiation is a popular method to produce microtextures on metal surfaces. However, the common laser-produced microtextures were hierarchical (multiscale), which may limit their applicability. In this paper, a method of two-step laser irradiation, combining first-step strong ablation and sequentially second-step gentle ablation, was presented to produce micron-rough surface with single-scale microtextures. The effect of laser fluence on the Ti–6Al–4V surface morphology and wettability were investigated in detail. The morphology results revealed that the microtextures produced using this method gradually evolved from multiscale to single-scale meanwhile from microprotrusions to microholes with increasing the second-step laser fluence from 0.0 to 2.4 J/cm2. The wettability and EDS/XPS results indicated that attributing to the rich TiO2 content and micron roughness produced by laser irradiation, all the two-step laser-irradiated surfaces exhibited superhydrophilicity. In addition, after silanization, all these superhydrophilic surfaces immediately turned to be superhydrophobic with close water contact angles of 155–162°. However, due to the absence of nanotextures, the water-rolling angle on the superhydrophobic surfaces with single-scale microtextures distinctly larger than those with multiscale ones. Finally, using the two-step laser-irradiation method and assisted with silanization, multifunctional superhydrophobic Ti–6Al–4V surfaces were achieved, including self-cleaning, guiding of the water-rolling direction and anisotropic water-rolling angles (like the rice-leaf), etc.
Highlights
Superhydrophobic metal surfaces with a water contact angle (WCA) larger than 150◦ have attracted great interest in both academic research and industrial applications [1,2,3]
Based on the principle of the two-step laser-irradiation method presented in the Section 2.1, it was indispensable to find the strong ablation-threshold fluence (SATF) of Ti–6Al–4V material
It was clearly seen that a few microscratches (MS) with sharp profiles were formed on the Ti–6Al–4V surface after polished by a series of SiC papers
Summary
Superhydrophobic metal surfaces with a water contact angle (WCA) larger than 150◦ have attracted great interest in both academic research and industrial applications [1,2,3]. It was found that controlling the wettability of the metallic biomaterial surfaces, such as titanium and its alloys, to be superhydrophobic could effectively enhance their hemocompatibility [4,5]. This was quite promising to be applied in the blood-contacting implants for reducing and even preventing the problems of hemolysis, coagulation and formation of thrombus. The obtained superhydrophobic surfaces were generally with a low WRA less than 5◦ These inevitable characteristics may reduce the flexibility and limit the applicability of laser irradiation technology
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