Superhydrophobic and transparent laser patterned glass surfaces with anti-icing, anti-fogging and anti-fouling functionalities

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This work discloses a robust fabrication strategy to produce transparent glass surfaces with multifunctional behavior including water-repellence and anti-icing properties. The approach combines a mild femtosecond large area laser patterning procedure for the surface engineering of micron-scale grooves in linear and cross motifs with the surface grafting of fluorinated tethered molecules. Optimal performance was achieved for ca. 15 µm deep and 26/37 µm wide grooves. Patterned glass with grooves separated by less than 100 µm presented a relatively high haze, which decreased to ca. 30/10% and even smaller values for inter-groove distances of 100/200 µm or higher. Thus, linear or rectangular patterns with groove separations of ca. 100 µm provided both a low haze and a long lasting repellence to water, other liquids and ice, even after exposure to environmental stressful conditions (UV, chemicals, mechanical erosion and freezing). A model based on air pocket retention inside the microgrooves has been proposed to account for the observed high hydrophobicity and even superhydrophobicity (WCA>150°, RoA<2°), long freezing delay times (∼180 min at -10°C), and low ice adhesion (∼15-20 kPa) found for laser treated glass samples with this range of inter-groove separation distances. The direct correlation found between wetting behavior and the surface-area ratio of laser treated glass surface sustains that grooves in the zones covered by water or ice entrap air pockets, which minimize the actual contact area with solid glass. Moreover, water condensation experiments conducted in air and in an environmental electron scanning microscope under saturated and oversaturated humidity conditions demonstrated an outstanding anti-fogging performance, which is attributed to the hindering of microdroplets growth within the grooves. These results, together with the self-cleaning and anti-fouling capacity of the engineered glass demonstrate that the developed laser-based methodology is capable of rendering a transparent and multifunctional glass well-suited for low temperature environments where fog, frost, snow or ice accumulation should be prevented or, at least, minimized.