Achieving amorphous micro-nano superhydrophobic structures on quartz glass with a PTFE coating by laser back ablation

Abstract

Superhydrophobic surfaces are typically prepared by composite processing and coating with low-surface-energy materials. Transparent, hard, and brittle materials (e.g., glass) are typically covered with low-surface-energy coating to form a superhydrophobic surface. In addition, achieving superhydrophobicity generally requires aging or modification to obtain a low surface energy by composite processing. Therefore, the preparation of superhydrophobic surfaces using one-step method is more efficient and economical. In this study, a method of realizing a superhydrophobic structure by laser back-facing direct etching is proposed. A superhydrophobic structure was immediately realized in one step using glass as the substrate and polytetrafluoroethylene (PTFE) as a coating. In addition, the surface morphologies of microstructures were studied for different laser parameters (laser single pulse energy and scanning rate). The results showed that at a laser pulse energy of 12 μJ and scanning rate of 100 mm/s, the contact angle (CA) of the obtained surface structure was 153 ± 2°, and the rolling angle (RA) was less than 2°, implying superhydrophobicity. At a low laser energy (less than 10 μJ) and a scanning rate lower than 80 mm/s, the sample broke during etching. At scanning rates of 100 mm/s and higher, the surface was not superhydrophobic. Further, at high laser energies (more than 12 μJ), the samples disintegrated. Scanning electron microscopy (SEM) showed that micro/nano structures were formed on the surface. The results of the elemental content analysis and X-ray photoelectron spectroscopy (XPS) indicated that the sample surface was attached to fluorine-containing nanoparticles.