Adjusting the distance between nanoparticles creates different colors
Pablo Sencillo-Abbado, Daniel Fran
The butterfly wing-inspired nanotechnology paint is so lightweight that when used on the Boeing 747, it could reduce the plane’s mass by half a ton.
Paint colors usually come from pigments, molecules that absorb certain wavelengths of light and reflect the rest. Some of these pigments pollute the environment, are difficult to remove, and can fade over time, especially in extreme heat or prolonged sunlight.
Now, Debashis Chanda and his colleagues at the University of Central Florida are using aluminum nanoparticle flakes instead, which trap and resonate specific wavelengths of light in the same way that specific sound wavelengths resonate in a wine glass. We have designed a paint that does not use any pigments. The trapped wavelengths mimic the absorption of pigments, giving nanomaterials their characteristic color.
This phenomenon is a structural resonance that also gives butterfly wings their color. “Color is not based on light-absorbing molecules, it’s just the structural arrangement of colorless substances,” he says.
To make the paint, Chanda and his team used an electron beam to deposit aluminum nanoparticles onto a mirror of the same material. The distance between these particles is set by how quickly they settle, which determines the wavelengths of light they “absorb”, leaving the remaining wavelengths for the color of the paint. This means Chanda and his team can easily choose paint colors.
The team then flakes these nanoparticle sheets and mixes the flakes with linseed oil to create a paint. The paint coating is only 150 nanometers thick, making it incredibly lightweight. A Boeing 747 covered in this needs just 1.3 kilograms of paint, instead of he 500 kilograms of regular paint, he said.
This paint is also highly reflective, so it can be used to keep your car or home cool. No pigment, so it will not fade.
John Pendley of Imperial College London says that while the optical effects of these nanostructures have been demonstrated in the laboratory for decades, using them to make paint is new. The challenge is to achieve these known effects in a fairly standard industrial process,” he says.
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