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Smudge-Free Surfaces

A coating based on candle soot sheds oil and water

Source: “Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating”
Doris Vollmer et al.
Science
335: 67–70

Results: A coating made of soot and silica repels both oil and water from glass and metal surfaces.

Why it matters: Eyeglasses, smart phones, medical devices, and the insides of gas turbines can all benefit from coatings that keep oil and other liquids from sticking to them. Researchers know what sorts of microscopic structures on a surface will repel oil, but the techniques used to make them have typically been too expensive for widespread commercial application. The new technique could prove much cheaper: it uses particles of soot as a template for the structures, so they don’t have to be carved using a process such as photolithography.

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Methods: The researchers held a glass slide over a candle flame to coat it with soot made of nanoscale spheres that stack up, resulting in a texture that repels oil. They covered the soot with a layer of silica to keep it from washing away. Then they baked the slide at 600 °C, which rendered the soot transparent.

Next Steps: Applying soot is cheap, but the method the researchers used for applying the silica is relatively expensive. They’re testing cheaper techniques.

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