Yeah! Science! Traditional paint is made from a binder, such as oil, and heavy metal pigments, such as cobalt, ochre and cadmium, which give blue, red and yellow colors, respectively. We use paint to color the artificial world, but in nature, creatures like butterflies and beetles show bright palettes without pigment — they use topography.
Take, for example, a peacock feather. The submicroscopic ridges and contours of the peacock feather refract light, creating the iridescent blue and green colors that we see. This natural coloring is called structural coloring.
Scientists from the University of Central Florida have developed a “first-of-its-kind” paint that mimics the structural coloring we observe in nature. Debashis Chanda, co-author of the study “Ultralight Plasmon Structural Color Paint”, and his team stumbled upon this discovery by chance.
The initial goal was to produce a long solid aluminum mirror using an electron beam evaporator. However, after numerous unsuccessful attempts, they noticed that aluminum sticks together, forming microscopic “nanostructures”. Grouping prevented the mirror from developing the highly reflective surface required for a mirror. Chanda said, “It was very annoying.”
However, he noticed that the aluminum electrons were agitated when ambient light hit the nanoparticles, causing them to oscillate. In addition, the electrons resonated with different wavelengths of light depending on the size of the nanoparticles. White light, falling on an uneven surface, reflected off its ridges before finally being reflected in one color.
“Just by changing the size of the nanoparticles, you can create all the colors,” Chanda told Wired.
Therefore, the team began to work on creating different colors of paint, growing aluminum nanostructures in a two-sided mirror, and then specially “dissolving” their sheets into dust of the consistency of powdered sugar. Then they mixed various colored materials with binders to make the paint.
Chanda said that because of its structural nature, only a very thin layer is required to color the surface. He says a drop the size of a raisin can stain both sides of the door. This property makes it ultralight, which can be extremely useful in the aviation industry.
A Boeing 747 requires about 1,000 pounds of paint. Chanda estimates that less than three pounds of his team’s structural paint will be needed to cover the jet, which will reduce the weight by more than 997 pounds. This may seem insignificant for a ship that weighs just under a million pounds. However, a small weight saving leads to significant fuel savings.
“Given that fuel is already the largest item of operating expenses [about 30 percent last year], airlines are always interested in improving fuel efficiency,” said a representative of the International Airline Trade Association.
For example, American Airlines estimates that it has saved 400,000 gallons of fuel and $1.2 million a year by removing only 67 pounds of pilot manuals from its planes. The company claims it saved another 300,000 gallons in 2021 by switching to lighter paint, which shed 62 pounds compared to its 737s.
Another advantage of this type of paint is its durability. Airlines repaint their planes up to four times a year due to the oxidizing effect of the sun. Structural colors do not fade in the sun, which means that repainting is only necessary when you want to change the color.
Another property of the paint helps to keep cool. Most planes are white to reflect as much light as possible. The absorbed infrared radiation is delayed, making the interior warmer.
Preliminary tests show that the team’s dye keeps the surface temperature 20-30 degrees Fahrenheit lower than traditional paint, regardless of color. Ideal for painting airplanes, cars, houses and other buildings. If it can lower the internal temperature even by 15 degrees, it saves a huge amount of energy used for air conditioning.
The only problem researchers are currently facing is scalability. They have the equipment to make small vials, but for real commercialization they will have to produce much more. The laboratory is looking for commercial partners who will help bring the paint to the market.
