One step fabrication and characterisation of stainless steel superhydrophobic surfaces using laser ablation

摘要

Superhydrophobicity of several natural plants and animals provides the excellent mechanical and physical properties. A number of research efforts have been directed to imitate and design the functional surfaces with superhydrophobicity. However, the durability of the metallic superhydrophobic surfaces is one of the main problems to block their applications. To overcome this problem, a one-step laser ablation based fabrication methodology for stainless steel superhydrophobic surfaces has been proposed. Through carefully optimizing the machining parameters, the superhydrophobic surfaces on stainless steel can be obtained without further surface coating treatment, which provides a cost-effective and high efficiency fabrication methodology. Since the top layer is directly formed from the bulk material, the long-term durability and resistance for mechanical wear and corrosion can be maintained. In addition, it is cheap for there is no further surface coating required. In order to investigate the inherent mechanism of wettability change on stainless steel, a number of extensive surface metrology and characterisation has been conducted. The relationships between the wettability and the surface topography have been extensively explored. It is noted that the surface topography can be modified by the laser ablation, and the contact angle can be improved or reduced due to the increase of the contact area. The wettability change is dependent on the laser fluence on the surface. Smaller laser fluence can improve the contact angle to some extent, and the larger one will make the surface superhydrophilic at the beginning. However, the superhydrophilic surfaces can change into superhydrophobic surfaces after several days. Through the experiments, it is noted that the reason for this wettability transition is not due to surface topography change but the chemistry alternation of the top layer. The developed fabrication and characterisation methodologies put one step forward for practical application of the metallic superhydrophobic surfaces in the industrial and academic sectors.