An energy-saving coating needs no pigments, and it keeps the surface beneath it 30 degrees cooler.
Debashis Chanda had trouble finding a physicist who could paint. The researchers in his nanoscience lab at the University of Central Florida had already worked out the kinks in the high-end machinery needed to create a revolutionary new kind of cooling paint. They had filled vials with vivid colors. But when it came time to show it off, they hit a wall. “We could barely draw a butterfly by hand, which is kind of a kid’s drawing,” says Chanda.
They did it anyway. The shape and the four-color design do look basic, but the simplicity is deceptive. If you zoom in deep—to invisible dimensions—this paint is almost nothing at all like the paint you know.
Color surrounds us in nature, and we re-create it with pigments. You can think of pigments as pulverized minerals, heavy metals, or chemicals that we swish into oil and spread over a canvas or car: Cobalt becomes blue; ochre red; cadmium yellow. “But nature has a very different way of creating color than we do,” Chanda says. Some of nature’s most vivid looks—the kind worn by peacocks, beetles, and butterflies—do their thing without pigment.
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Those colors come from topography. Submicroscopic landscapes on the outer surfaces of peacock feathers, beetle shells, and butterfly wings diffract light to produce what’s known as structural color. It’s longer-lasting and pigment-free. And to scientists, it’s the key to creating paint that is not only better for the planet but might also help us live in a hotter world.
In a paper published this month in Science Advances, Chanda’s lab demonstrated a first-of-its-kind paint based on structural color. They think it’s the lightest paint in the world—and they mean that both in terms of weight and temperature. The paint consists of tiny aluminum flakes dotted with even tinier aluminum nanoparticles. A raisin’s worth of the stuff could cover both the front and back of a door. It’s lightweight enough to potentially cut fuel usage in planes and cars that are coated with it. It doesn’t trap heat from sunlight like pigments do, and its constituents are less toxic than paints made with heavy metals like cadmium and cobalt.
Oooh… Iridescent aircraft and train liveries to come!