Researchers from the University of Central Florida (US) created the first environmentally friendly, large-scale and multicolour alternative to pigment-based colourants, inspired by butterfly wings.

Common paints and colourants are pigment based, which means new molecules need to added for every colour present. In nature, such as butterfly wings, on the other hand, colours are structural, and typically two colourless materials produce all colours with their geometrical arrangement. With this, they control the way the light is reflected, scattered or absorbed.

These structural colours use only metals and oxides, and tare therefore more environmentally friendly than pigment-based colours that use artificially synthesized molecules.

Using these principles, the research group developed a so-called plasmonic paint, which utilizes nanoscale structural arrangement of colourless materials, aluminium and aluminium oxide, instead of pigments to create colours. Then they combined their structural colour flakes with a commercial binder to form long-lasting paints of all colours.

The paint has three main advantages, aside from being more environmentally friendly. Normal colour fades because pigment loses its ability to absorb photons, as opposed to structural colours. In addition, because plasmonic paint reflects the entire infrared spectrum, less heat is absorbed by the paint, resulting in the underneath surface staying 25 to 30 degrees Fahrenheit cooler than it would if it were covered with standard commercial paint.

Finally the paint is extremely lightweight, with full colouration of only 150 nanometres. To compare, a Boeing 747 air plane could be covered in 1.5 kilograms of plasmonic paint, which normally requires 500 kilograms or conventional paint.

Photo: University of Central Florida