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Nanopowders, Thin Films, and Devices | |
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 nGimat is actively developing self-cleaning coatings for architectural glass, automotive glass, solar cells, space applications, and other specialty products. The natural cleanness observed on lotus and other plant leaves first inspired development of superhydrophobic self-cleaning surfaces. Studies of lotus leaves 
by scanning electron microcopy (SEM) revealed that the key features
of the lotus leaf are a microscopically rough surface consisting of
an array of randomly distributed micropapillae with diameters
ranging from 5 to 10 mm. These micropapillae are covered with waxy
hierarchical structures in the form of branch-like nanostructures
with average diameters of about 125 nm. The water contact angle on a
lotus leaf is higher than 160° with a rolling angle of about
2°, which would be considered a high performance
superhydrophobic self-cleaning surface. For reference, the droplet
on an nGimat-coated surface shown here has a contact angle of
greater than 165°.Water droplets coming in contact with a superhydrophobic surface (contact angle >150°) form nearly spherical beads. The contaminants, either inorganic or organic, on such surfaces are picked up by water droplets or adhere to the water droplet and are removed from the surface when the water droplets roll off. The combination of low surface energy and micro- and/or nano-structured features, which can certainly reduce the contact area between the surface and water droplets, form superhydrophobic surfaces. nGimat has used its CCVD process to deposit thin films with nanostructured surfaces that mimic the lotus leaf effects but in a controllable process that allows incorporation of other properties, such as transparency. On nGimat-coated glass, metal, or plastic surfaces, the water droplets are nearly perfect spheres. Though a relatively recent addition to nGimat's area of interest, the CCVD process has enabled rapid development of promising small scale prototype coatings. Glass coaters are evaluating these coatings for a variety of applications. |
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