One-step fabrication of superhydrophobic hierarchical structures by femtosecond laser ablation

• Published in: Applied surface science 2014-09, Vol.313, p.411-417
• Main Authors: Rukosuyev, Maxym V., Lee, Jason, Cho, Seong Jin, Lim, Geunbae, Jun, Martin B.G.
• Format: Article
• Language: English
• Subjects: Ablation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Femtosecond; Femtosecond laser ablation; Hierarchical structure; Hydrophobic surface; Hydrophobicity; Laser ablation; Laser machining; Physics; Structural steels; Surface chemistry; Surface properties
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.05.224

•Superhydrophobic surface patterns by femtosecond laser ablation in open air.•Micron scale ridge-like structure with superimposed submicron convex features.•Hydrophobic or even superhydrophobic behavior with no additional silanization. Hydrophobic surface properties are sought after in many areas of research, engineering, and consumer product development. Traditionally, hydrophobic surfaces are produced by using various types of coatings. However, introduction of foreign material onto the surface is often undesirable as it changes surface chemistry and cannot provide a long lasting solution (i.e. reapplication is needed). Therefore, surface modification by transforming the base material itself can be preferable in many applications. Femtosecond laser ablation is one of the methods that can be used to create structures on the surface that will exhibit hydrophobic behavior. The goal of the presented research was to create micro and nano-scale patterns that will exhibit hydrophobic properties with no additional post treatment. As a result, dual scale patterned structures were created on the surface of steel aluminum and tungsten carbide samples. Ablation was performed in the open air with no subsequent treatment. Resultant surfaces appeared to be strongly hydrophobic or even superhydrophobic with contact angle values of 140° and higher. In conclusion, the nature of surface hydrophobicity proved to be highly dependent on surface morphology as the base materials used are intrinsically hydrophilic. It was also proven that the hydrophobicity inducing structures could be manufactured using femtosecond laser machining in a single step with no subsequent post treatment.