Paint that never fades

Researcher at Wageningen University & Research (WUR) developed a type of paint of which the colour never fades, inspired by animals like peacocks and butterflies.

Normally, colour is made by absorbing a certain part of light and reflecting another. You only see the reflected light, which looks like a certain colour. When the light is absorbed, chemical processes start to decay the pigment.

Not all colours work this way, though. Butterfly wings and peacock feathers do not absorb light; the part that isn’t reflected moves straight ahead. This gives a so-called photonic colour, which keeps its intensity for a long time. Some insect fossils of millions of years old still have the same bright colours the creature had when alive.

The researchers managed to replicate the nanostructures from the animal kingdom by stacking tiny plastic spheres. In between the sphere, they added silica. During heating the plastic melts away and the silica becomes hard, leaving air in place of the spheres. The size of the sphere dictates the colour. The smallest spheres create blue, then green, and the largest purple.

Red is currently impossible, because structures that reflect red also reflect blue, becoming purple. In nature, there is no red phonic colour. The researchers aim to work around that by using a mix of sphere sizes that don’t reflect blue. Making non-pastel colours is also difficult, seeing that the material reflects light, but this could be countered by adding charcoal.

The resulting paint is non-toxic, and poses no health issues. One of the researchers used to make a few paintings inspired by Van Gogh, like the one shown above.

Currently, the production costs are too high as the paint is lab-fabricated, but the aim is to scale-up the project to bring those down.

Photo: WUR