Fabrication of superhydrophilic surface on metallic nickel by sub-nanosecond laser-induced ablation

Abstract

The alterations of wettability on metallic nickel surface by sub-nanosecond laser (1 ns, 1064 nm) induced surface modification was investigated. An approximate linear relation between surface contact angles (CAs) and accumulated fluence was established, which shows that with proper combinations of laser parameters, CA would reduce significantly from its initial value (∼96°) to approximately 3.1°. The microscopic inspection and roughness test reveal that the surface roughness on irradiated areas would increase remarkably due to the distribution of micro/nanoparticels and cracks that induced by laser ablation, which consequently improve the hydrophilic performance effectively. On the other hand, elemental analyses by use of XPS demonstrate that the nickel dioxides and nickel hydroxides were generated as the main components covering the self-organized structures. Such increasement in oxygen content, especially the growth of NiO and hydroxyl group provides a prerequisite in the transformation of nickel from initial hydrophobicity to hydrophilicity. And the integrated effects of surface morphology, roughness and chemistry ultimately led to the formation of super-wettability. The investigation indicates that, the sub-nanosecond laser is an effective tool to transform the metallic nickel into functional material with a highly hydrophilic surface by creating controllable topographical features and chemical properties on its surface.

A metallic anti-biofouling surface with a hierarchical topography containing nanostructures on curved micro-riblets

“…Nickel oxide is hydrophilic. 23 As the initial contact angle of bare nickel coated with nickel oxide was 56.7°, the apparent contact angle decreased as the roughness increased. The contact angles of surfaces with nanostructures and micro-riblets were 26.9° and 18.1° respectively.…”

“…Nickel oxide is hydrophilic. 23 As the initial contact angle of bare nickel coated with nickel oxide was 56.7°, the apparent contact angle decrease as the roughness increase according to the Wenzel equation. 28 As we superimposed the nanostructures on the micro-riblets, the hierarchical structures exhibited superhydrophilicity.…”

“…Although nickel is easily oxidized in air, anodic oxidation 22 was performed to prepare a uniform nickel oxide layer and induce superhydrophilicity. 23 We used scanning electron microscopy (SEM), atomic force microscopy (AFM), contact-angle measurement, and wear-resistance tests to characterize the surface. The measured static contact angle of the hierarchical structures was less than 1°.…”

The effect of femtosecond laser fluence and pitches between V-shaped microgrooves on the dynamics of capillary flow

“…In general, performance of superwicking surfaces depends on wettability of a solid, which is mainly affected by surface energy, liquid viscosity and the morphology of the solid surface [12] , [13] . Based on these factors, various techniques have been developed to intrinsically change the wettability of solid surfaces, such as plasma treatment [14] , [15] , chemical etching [16] , [17] , [18] , mechanical treatment [2] , [19] , [20] and laser ablation [21] , [22] , [23] , [24] , [25] , [26] . Among these methods, laser ablation technology has more advantages such as simple operation and no need for a complex processing environment.…”

“…Kai Yin et al processed a line-patterned superwetting surface on sapphire by using a femtosecond laser, and they found that the performance of superwicking property is enhanced with the increase of the width and depth of the microgrooves structures [25] . HuaZhong Zhu et al used a sub-nanosecond laser to modify a nickel surface, which significantly enhances the wicking property and reduces the contact angles from ~96° to ~3.1° [26] .…”