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ISSUE #51

DESIGN & NATURE REIMAGINED

MARISA MORBY​

Sometimes when I'm finding things to write about, I stumble on something that I didn't know existed. Recently it was structural color. Structural color is created by the reflection and scattering of light. This is different than color created by pigments or dyes, where color is created by the pigment or dye absorbing all of the light except for a specific wavelength of light. The one color that's not absorbed is then the color that you see. Instead, structural color results from how nanoparticles lay against each other and reflect wavelengths back into our eyes. Today I want to explore how structural color works and how scientists and artists are using it.

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design

This is an area where I see a large overlap between art and science, and that intersection is fascinating. Back in 2010 Kate Nichols, an artist at UC Berkeley, wanted to create the vibrant colors that she saw on Blue Morpho butterfly wings. And in her search to find that color she found the laboratory at Berkeley, because the vibrant blue that makes the Blue Morpho butterfly so stunning is created by structural color in the makeup of the butterflies wings. She became the first artist-in-residence at the Lawrence Berkeley National Laboratory, synthesizing nanoparticles to create structural color for her paintings. You can learn more about how structural color works and watch her process here.

As scientists have been learning more about structural color, nonoparticles, and microns they're also learning that paint with structural color could be a way to reduce energy consumption. Yes, you read that right. Debashis Chanda, a researcher at the University of Central Florida has made structural paint using aluminum and aluminum oxide. ​

The paint is made entirely of metal and derives it's color from the structure of the particles, which reflect light and different wavelengths. This light reflection keeps the surface area under the paint up to 30 degrees cooler than with traditional paints, which means that buildings using this paint could use less energy cooling the building. It's also extremely lightweight. A Boeing 747 normally requires about 1,000 pounds of conventional paint. It only requires 3 pounds of structural paint. "American Airlines once figured that cutting 67 pounds (30.4 kilograms) from its flights could save 400,000 gallons (1,514,000 liters) of fuel every year. Structural paint could save over 16 times as much." And based on what we know about how the particles in structural color work, it's also expected that these paints will stand the test of time and last far longer than traditional pigmented paints. Because pigmented paints are colored by organic materials, the paint can fade and break down over time from wear and tear and cause pollution in the form of microplastics. But since the color that's produced in structural color paint is made from metal and created by the actual structure of the atoms in the paint, it's likely that it will take much, much longer for that paint to fade or break down.

nature

Color helps animals camouflage themselves, communicate, or find a mate. In plants, color is typically used to attract pollinators. In animals or plants that have structural color, the nanoscale structure of the material (like a butterfly wing) reflects specific wavelengths of light, so that when light hits that material it bounces off it in a way that makes your eye see a specific color. Because structural color relies on reflecting light, it creates deep, vibrant hues, like the colors we see on butterfly wings, hummingbird feathers, abalone shells, or peacock feathers.
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Most of the reds and yellows that we see in animals are created through pigments. Animals typically become red or yellow through the carotenoids they eat in their food (I talked about carotenoids in leaves last week). This same effect is what makes flamingos pink! They eat algae, brine shrimp, and brine fly larvae, all of which are high in beta-carotenes and turn them pink. Flamingos are actually born a dull gray. In other cases, the browns and blacks we see are the result of the pigment of melanin, like in human skin, and animals that are black or brown in color.

Structural color in plants is more rare, but is seen in Begonia rex ‘Silver Cloud’, which has a silvery sheen to its leaves, Ranunculus (buttercup), which uses yellow pigmentation and structural color to create a vibrant yellow, and Pollia condensata (marble berry), which has a deep blue, as you can see below. Structural color is much more prevalent in marine organisms like mollusks, cephalopods, algae, and shells.

reimagine

Kew Gardens in the UK often highlights artists combining art and nature. In 2021 they got access to paints from Pure Structural Colour and botanical artist Coral G. Guest was the first artist who got to try it. She chose to do a painting of Pollia condensata seeds, also called marble berries. Structural color creates the deep purple-blue hues in this berry and it almost shines, just like her painting. You can see her video about the painting here.