Debashis Chanda, a nanoscience researcher with the University of Central Florida, and his team have created a way to mimic nature’s ability to reflect light and create beautifully vivid color without absorbing any heat like traditional pigments do.
Chanda’s research, published in the journal Science Advances, explains and explores structural color and how people could use it to live cooler in a rapidly warming world.
Structural colors are created not from traditional pigmentation but from the arrangement of colorless materials to reflect light in certain ways. This process is how rainbows are made after it rains and how suncatchers bend light to create dazzling displays of color.
One driver for the researchers: A desire to avoid toxic materials
To create these colors, synthetic materials like heavy metals are used to create vivid paints.
“We use a lot of artificially synthesized organic molecules, lots of metal,” Chanda told NPR. “Think about your deep blues, you need cobalt, a deep red needs cadmium. They are toxic. We are polluting our nature and our whole habitat by using this kind of paint. So one of the major motivations for us was to create a color based on non-toxic material.”
So why can’t we simply use ground-up peacock feathers to recreate its vivid greens, blues and golds? It’s because they have no pigment. Some of the brightest colors in nature aren’t pigmented at all, peacock feathers included.
These bright, beautiful colors are achieved by the bending and reflection of light. The way the structure of a wing, a feather or other material reflects light back at the viewer. It doesn’t absorb any light, it beams it back out in the form of a visible color, and this is where things get interesting.
Chanda’s research began here, with his fascination with natural colors and how they are achieved in nature.
Beyond just the beautiful arrays of color that structure can create, Chanda also found that unlike pigments, structural paint does not absorb any infrared light.
Infrared light is the reason black cars get hot on sunny days and asphalt is hot to the touch in summer. Infrared light is absorbed as heat energy into these surfaces — the darker the color, the more the surface colored with it can absorb. That’s why people are advised to wear lighter colors in hotter climates and why many buildings are painted bright whites and beiges.
Chanda found that structural color paint does not absorb any heat. It reflects all infrared light back out. This means that in a rapidly warming climate, this paint could help communities keep cool.
Chanda and his team tested the impact this paint had on the temperature of buildings covered in structural paint versus commercial paints and they found that structural paint kept surfaces 20 to 30 degrees cooler.
This, Chanda said, is a massive new tool that could be used to fight rising temperatures caused by global warming while still allowing us to have a bright and colorful world.
Unlike white and black cars, structural paint’s ability to reflect heat isn’t determined by how dark the color is. Blue, black or purple structural paints reflect just as much heat as bright whites or beige. This opens the door for more colorful, cooler architecture and design without having to worry about the heat.
A little paint goes a long way
It’s not just cleaner, Chanda said. Structural paint weighs much less than pigmented paint and doesn’t fade over time like traditional pigments.
“A raisin’s worth of structural paint is enough to cover the front and back of a door,” he said.
Unlike pigments which rely on layers of pigment to achieve depth of color, structural paint only requires one thin layer of particles to fully cover a surface in color. This means that structural paint could be a boon for aerospace engineers who rely on the lowest weight possible to achieve higher fuel efficiency.
Source: Scientists create an eco-friendly paint : NPR