Laser Texturing of Soda-Lime Glass Surfaces with Extreme Wettability Contrast

The ability to create extreme wettability contrast on glass surfaces has significant implications for applications such as self-cleaning systems, fluid manipulation, anti-fogging, and open-surface microfluidics. However, achieving this contrast in a controllable manner remains challenging. In this study, soda-lime glass surfaces are engineered with extreme wettability properties following a two-step approach. First, laser ablation using either Direct Laser Writing (DLW) or Direct Laser Interference Patterning (DLIP) based on a ns-pulsed UV (266 nm) source was used to microtexture glass with single-scale or hierarchical patterns. Due to the increased roughness, the laser-treated surfaces become superhydrophilic with water contact angles below 10°. To induce hydrophobicity, the laser-textured surfaces are subsequently sprayed with a hydrophobizing agent based on a chemically active perfluoropolyether compound. This process converts all hydrophilic surfaces into highly hydrophobic ones, exhibiting water contact angles exceeding 140° for the hierarchical surfaces. Surface free energy (SFE) measurements revealed highly inert hydrophobic surfaces with SFE values below 1 mN/m, while values exceeding 80 mN/m were obtained for the superhydrophilic glass. Finally, the potential of glass surfaces with extreme wetting contrast is demonstrated by fabricating superhydrophilic channels surrounded by hydrophobic areas that are able to spontaneously transport water.