Laser Patterning of Superhydrophobic transparent glass surfaces with anti-fogging and anti-icing applications

Abstract

This work addresses the fabrication of transparent glass surfaces with superior water-repellence (i.e., superhydrophobicity), and related functional properties such as omniphobicity, anti-fogging and anti-icing responses. Surfaces have been processed by means of mild femtosecond laser patterning combined with the grafting of fluorinated tethered molecules. Controlling the laser scan and ablation conditions permits the fabrication of under-design grooves with cross and lineal morphologies and separations between 10 and 500 um. These patterns provide a high transparency and repellence to liquids and ice over large areas. The best performance is obtained for cross or parallel line patterned glass with microgrooves separated by 100 um and 15 um depth thanks to 5 laser scanning repetitions. These surfaces present a stable Cassie-Baxter wetting state and very low ice-adhesion strength while keeping up to 80 % of optical transmittance in the visible region. Anti-fouling tests, along with freezing and thawing cycles on these surfaces, have demonstrated a remarkable and durable self-cleaning response, even under environmentally stressful conditions. Water condensation experiments conducted under atmospheric conditions, as well as in an environmental electron scanning microscope, have revealed important issues related to the formation of supercooled water droplets. These experiments show that the patterned breakdown of surface properties effectively prevents extensive fogging and water accumulation. This feature is particularly crucial for outdoors and low temperature applications where the preservation of transparency is essential.