Butterflies inspire world's lightest paint
Aluminum is key to colorants 300x lighter than pigment paint Metal Tech News - May 12, 2023
Last updated 5/16/2023 at 2:25pm
Inspired by the wide variety of brilliant colors adorning the wings of butterflies, University of Central Florida researcher Debashis Chanda has created the world's lightest paint using two materials that do not have any color of their own – aluminum and aluminum oxide.
The plasmonic paint developed by Chanda is so lightweight it would only take about three pounds to coat an entire Boeing 747 aircraft, which is orders of magnitude less than the 1,000 lb of traditional pigment paints.
And, as a kicker, the butterfly-inspired paint never fades and helps to cool the exterior of any surface it coats.
How is it that paint made from materials with no inherent color can be so lightweight, long-lasting, and energy-saving?
The answer comes from the way the nature-inspired paint creates color. Instead of pigments, the structural colorants used in Chandra's aluminum-based paints control how light is reflected, scattered, or absorbed based purely on the geometrical arrangement of nanostructures.
This structural coloring technique is nothing new; the natural world has been perfecting this means of creating colors for millions of years.
"The range of colors and hues in the natural world are astonishing - from colorful flowers, birds and butterflies to underwater creatures like fish and cephalopods," Chanda says. "Structural color serves as the primary color-generating mechanism in several extremely vivid species where geometrical arrangement of typically two colorless materials produces all colors. On the other hand, with manmade pigment, new molecules are needed for every color present."
Since Chandra's plasmonic paint does not depend on bulky pigment molecules, a 150-nanometer-thick coating is all that is needed to achieve the desired coloration. By way of comparison, a human red blood cell is roughly 9,000 nanometers across.
The ability to create vibrant colors with a coating 60 times thinner than a blood cell is the reason why the aluminum-based paint is so lightweight.
And this nanoscale thin coating will also outlast pigment-based paints.
"Normal color fades because pigment loses its ability to absorb photons," Chanda says. "Here, we're not limited by that phenomenon. Once we paint something with structural color, it should stay for centuries."
Structural paints also offer a couple of environmental advantages.
Because plasmonic paint reflects the entire infrared spectrum, less heat is absorbed by the paint, resulting in the underneath surface staying 25 to 30 degrees Fahrenheit cooler than it would if it were covered with standard commercial paint.
"Over 10% of total electricity in the U.S. goes toward air conditioner usage," Chanda said. "The temperature difference plasmonic paint promises would lead to significant energy savings. Using less electricity for cooling would also cut down carbon dioxide emissions, lessening global warming."
Aside from the fact that you need roughly 300 times less to accomplish the same task, structural paints are considered to be more environmentally friendly because they use metals and oxides instead of the artificially synthesized molecules produced for pigment paints.
Chandra and his research team at the University of Central Florida have combined their structural color flakes with a commercial binder to form long-lasting paints of all colors.
Because plasmonic paints are still being produced at the lab scale, they currently are not cost-competitive with traditional paints.
"The conventional pigment paint is made in big facilities where they can make hundreds of gallons of paint," the University of Central Florida NanoScience Technology Center professor noted. "At this moment, unless we go through the scale-up process, it is still expensive to produce at an academic lab."
The nanoscience professor says the next steps of the project include further exploration of the paint's energy-saving and other environmental advantages to improve its viability as commercial paint.
"We need to bring something different like, non-toxicity, cooling effect, ultralight weight, to the table that other conventional paints can't," he said.
Information on licensing this technology can be found in the Inorganic Paint Pigment for Vivid Plasmonic Color technology sheet.