Researchers at the University of California, Riverside, have created a nanoparticle-based paint that can produce vivid colours without the need for any pigments. Instead, the paint relies on what is known as structural colour, which is caused by the reflection of light off a surface. The researchers stumbled upon the effect by accident while trying to make a long, continuous mirror using an electron beam evaporator. They found that groups of aluminium atoms, called ‘nanoislands,’ disrupted the mirror’s polish, and that the size of the islands could be used to create specific colours. The paint is so thin that it takes only 1.3 kg to cover the same space as 500 kg of conventional paint, prompting potential uses on aircraft and other vehicles.
The study, published in ACS Nano, explains that structural colour is already used to great effect by nature. The blue of a Morpho butterfly, for example, is created by layers of tiny aluminium particles in its wings. Conventional paint, however, creates colours by using pigments that absorb certain wavelengths of light and reflect others. The researchers found that aluminium nanoislands could reflect colours thanks to the impact they had on the orbiting electrons of the aluminium atoms themselves. Varying the size of the nanoislands produces different colours. The team created a prosaic butterfly to demonstrate the process.
The ultra-thin layer of paint developed in the study could be used in a variety of applications, from decorations to clothing dyes, according to the researchers. The most obvious application is in the aviation sector. The researchers’ calculations suggest a 747 could be saved more than 1,000 lb in weight through the use of nanoparticle-based paint, which in turn would save on fuel. Other uses could include cosmetic pastes and even polymer-based colour-coded microbeads for medical use. Aviation is likely to provide the biggest market, however, as fuel costs remain a major challenge for airlines.