Instead of pigment-based coloured paint, which requires artificially synthesised molecules, a researcher at the University of Central Florida (UCF) has developed an alternative way to produce coloured paint that is more natural, environmentally friendly and lightweight.
Debashis Chanda, a professor in UCF’s NanoScience Technology Center, drew his inspiration from butterflies to create the first environmentally friendly, large-scale and multicolour alternative to pigment-based colourants, which could contribute to energy-saving efforts and help reduce global warming.
“The range of colours and hues in the natural world are astonishing — from colourful flowers, birds and butterflies to underwater creatures like fish and cephalopods,” Chanda said.
“Structural colour serves as the primary colour-generating mechanism in several extremely vivid species where geometrical arrangement of typically two colourless materials produces all colours. On the other hand, with manmade pigment, new molecules are needed for every colour present.”
Based on such bio-inspirations, Chanda’s research group innovated a plasmonic paint, which uses nanoscale structural arrangement of colourless materials – aluminium and aluminium oxide – instead of pigments to create colours.
While pigment colourants control light absorption based on the electronic property of the pigment material and hence every colour needs a new molecule, structural colourants control the way light is reflected, scattered or absorbed based purely on the geometrical arrangement of nanostructures.
Image credit: University of Central Florida
Such structural colours are environmentally friendly as they only use metals and oxides, unlike present pigment-based colours that use artificially synthesised molecules.
The researchers have combined their structural colour flakes with a commercial binder to form long-lasting paints of all colours.
“Normal colour 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 colour, it should stay for centuries.”
Additionally, because plasmonic paint reflects the entire infrared spectrum, less heat is absorbed by the paint, resulting in the underneath surface staying 25 to 30°F cooler than it would if it were covered with standard commercial paint, the researcher said.
“Over 10 per cent of total electricity in the US 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.”
Plasmonic paint is also extremely lightweight, Chanda added. This is due to the paint’s large area-to-thickness ratio, with full colouration achieved at a paint thickness of only 150 nanometers, making it the lightest paint in the world.
The paint is so lightweight that only around 3lb of plasmonic paint would be needed to cover a Boeing 747, which normally requires more than 1,000lb of conventional paint, according to Chanda’s estimates.
Chanda says his interest in structural colour stems from the vibrancy of butterflies: “As a kid, I always wanted to build a butterfly. Colour draws my interest.”
The next steps of the project include further exploration of the paint’s energy-saving aspects to improve its viability as commercial paint.
“The conventional pigment paint is made in big facilities where they can make hundreds of gallons of paint,” he says. “At this moment, unless we go through the scale-up process, it is still expensive to produce at an academic lab,” Chanda said.
“We need to bring something different like non-toxicity, cooling effect, ultra-lightweight to the table that other conventional paints can’t.”
The research paper – ‘Ultralight plasmonic structural colour paint’ – has been published in the journal Science Advances.
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