Quantification of superhydrophobic functionalization for laser textured metal surfaces

Abstract

Laser texturing is a facile method to promote modified surface wetting properties. While most laser textured metal surfaces are natively superhydrophilic, here we establish a quantitative relationship between post-texturing chemical modification and water contact angles from ca. 80° < θw < 180°. A nanosecond laser-based high-throughput surface nanostructuring (nHSN) method is used to texture aluminum alloy surfaces. The textured surfaces are immersed in ethanol solutions of chlorosilane reagent [CF3(CF2)5(CH2)2SiCl3] (FOTS) at different concentrations and different times to achieve superhydrophobicity. The role played by the two chemical treatment parameters, concentration and treatment time, is investigated and quantified. Water contact angle, reflection-based infrared spectroscopy and energy-dispersive X-ray spectroscopy are used to characterize the functionalized surface. The goal of this research is to quantify the effects of surface chemical modification on the resulting material functionality using surface sensitive spectroscopic techniques. Our results show that both the solution concentration and the immersion treatment time play significant roles in the attachment of functional groups (-CF2-, -CF3) on surface. Further, concentrations of FOTS as low as 0.1% with six hours of chemical immersion treatment, or short treatment times as low as three hours with 0.5% FOTS solution are adequate to achieve superhydrophobicity.