Role of Surface Chemistry on Wettability of Laser Micro-/Nanostructured Metallic Surfaces

Over the past few decades, short and ultrashort pulsed lasers have been used extensively to manipulate the surface properties of almost all solid materials. Among them, the pulsed laser-generated superhydrophobic/superhydrophilic surfaces have attracted considerable interest from both research and industry owing to their potential in self-cleaning, anticorrosion, anti-biofouling, and deicing applications. A transition in the surface wettability from (super)hydrophilicity to (super)hydrophobicity of laser micro-/nanostructured metallic surfaces over time has been reported by many authors over the past decade. These studies suggest the critical role of surface chemistry in controlling the final wetting state of laser-textured metallic surfaces. In this chapter, we demonstrate how surface chemistry varies over time after being exposed to ambient air, liquids, gases, and heat treatments and how those changes result in wettability transitions. The suggested mechanisms leading to the transition from (super)hydrophilicity to (super)hydrophobicity are reviewed. The reliability and reproducibility of X-ray photoelectron spectroscopy and contact angle measurement data are assessed. Finally, the existing challenges in describing the phenomenon of wettability transition and future prospects for explaining the wettability transition are presented.