Nanotech ink provides vibrant color that won’t fade

The butterfly-wing-inspired nanotech paint is so light that its use on a Boeing 747 could reduce the aircraft’s weight by half a ton.

Paint color usually comes from pigments, which are molecules that absorb certain wavelengths of light and reflect others. Some of these pigments can be environmentally polluting, difficult to remove, and may fade over time, especially in extreme heat or prolonged sunlight.

Now, Debachis Chanda of the University of Central Florida and colleagues have developed a pigment-free paint that instead uses flakes of aluminum nanoparticles that trap and resonate with specific wavelengths of light, just like specific wavelengths of sound can resonate with a wine glass. The captured wavelengths are similar to absorption in pigments, which gives the nanomaterial its characteristic color.

This phenomenon is a structural resonance that also gives color to the butterfly’s wing. “Color doesn’t depend on any light-absorbing molecule, it’s just a structural arrangement of colorless materials,” says Chanda.

To make the paint, Chanda and his team used an electron beam to deposit aluminum nanoparticles on a mirror made of the same material. The distance between these particles, which is determined by how quickly the particles settle, determines the wavelengths of light they “absorb” and the remaining wavelengths are the color of the paint. This means that Chanda and his team can easily choose the color of the paint.

The team then separated these sheets of nanoparticles into flakes and mixed them with linseed oil to make paint. The paint layer only needs to be 150 nanometers thick, making it incredibly light. A painted Boeing 747 would require only 1.3 kg of paint instead of 500 kg of conventional paint, Chand said.

The paint is also highly reflective so it can be used to cool cars or homes, and the lack of pigment means it won’t fade.

The optical effects of these nanostructures have been demonstrated in the lab for decades, says Imperial College London’s John Pendry, but creating paint with them is new. “The achievement that these guys have is that they have taken these known effects and implemented them in a fairly standard industrial process,” he says.