Fabrication of a Super-hydrophobic Surface on Metal Using Electrodeposition

Abstract

In this research, the fabrication process of a super-hydrophobic metallic surface using electrodeposition was investigated. The super-hydrophobic metallic surfaces are expected to broaden the practical application field of super-hydrophobicity that has been limited to some types of films for self-cleaning and preventing the pollution. Re-entrant structure and hierarchical structure have advantages in water repellent property of surfaces. Fabrication processes using electrodeposition that has an advantage in diversifying the surface morphology and property were proposed. The re-entrant structure plays an important role in forming a super-hydrophobic surface on intrinsically hydrophilic material. A micro pillar array with a re-entrant structure was fabricated through a sequential process of laser ablation, insulating, mechanical polishing and electrodeposition. Spacing of the micro pillars in the array played a major role in hydrophobicity of the structure that was confirmed by measuring the water contact angle. Surface morphology changed relative to the parameters of the laser ablation process and electrodeposition process. Under gradual increase in current density during the electrodeposition process, surface morphology roughness was maximized for fabricating a super-hydrophobic surface. Material combinations of substrate and deposited material were also investigated. Fabrication process for hierarchical structure is consisted of laser ablation for micro-structuring and electrodeposition for hierarchical structuring. Under excessive current density condition in electrodeposition, hierarchical structure was fabricated with low surface energy resulting from copper oxide. Fabricated structures with more than a hundred micrometer in depth have a super-hydrophobicity. The role of copper oxide and hierarchical structure were confirmed by oxidation test of fabricated structures because copper oxide had an undetectable thickness by XRD and XPS. To evaluate the dynamic robustness of hydrophobicity, experiments with dynamic contact angle and squeezing test were carried out.