Rugged, ultra-hydrophobic surface design.

Scientists create powerful super-hydrophobics by providing hydrophobic nanostructure designs and durable microstructure designs.
's ability to keep ultra-hydrophobic surfaces dry, self-cleaning and avoiding bioscaling is attractive for biotechnology, medicine and heat transmission applications. Water droplets that come into contact with these surfaces must have a large apparent contact angle (greater than 150 degrees) and a smaller roll-off angle (less than 10 degrees)

. This is possible on surfaces with low surface chemical properties and roughness of micron or nanoscale surfaces, minimizing contact between liquid and solid surfaces.
, however, rough surfaces (only a small fraction of the total area in contact with liquids) are subjected to high local pressure under mechanical loads, making them fragile and prone to wear. In addition, wear exposes the material below and may cause the local properties of the surface to change from hydrophobic to hydrophobic, resulting in water droplets being nailed to the surface. Therefore, mechanical strength and hydrophobicity have been assumed to be mutually exclusive surface properties.
"Pockets"
equipped with highly waterproof and mechanically fragile nanostructures now show that strong ultra-hydrophobicity can be achieved by constructing surfaces on two different length scales, where nanostructure designs provide water resistance and microstructure designs provide durability. Microstructures are interconnected surface frames that contain "pockets" containing highly hydrophobic and mechanically fragile nanostructures. The surface frame acts as "armor" to prevent abrasives larger than the frame size from removing nanostructures.
researchers applied this strategy to a variety of substrates, including silicon, ceramics, metal and clear glass, and showed that the hydrophobicity of the resulting ultra-hydrophobic surfaces remained even after being abrasive by sandpaper and sharp steel blades. They argue that this transparent, mechanically strong self-cleaning glass can help eliminate dust pollution that reduces the efficiency of solar cells. The design strategy also guides the development of other materials that require effective self-cleaning, anti-fouling or heat transmission in harsh working environments.
the study has been published in Nature Volume 582 (2020).
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