Morpho butterfly.
LeeRobertsMe/Wikimedia Commons Morpho butterfly.

Structural color is a natural phenomenon that continues to intrigue scientists. Structural color is abundant in nature—consider the wings of the morpho butterfly or the feathers of the spangled cotinga, for example. It is imparted by the surface nanostructure of a material. Unlike conventional paints and dyes used in manufactured products, structural color never fades—as long as the nanostructures remain intact, the color will persist even in harsh environmental conditions.

Scientists at the Harvard School of Engineering and Applied Sciences have developed a method for recreating structural color in man-made materials. The researchers filled microcapsules with an aqueous solution of small, disordered particles. Drying out the capsules brought the particles closer together, producing a color. Based on how much they dried out the capsules, the researchers could produce different colors.

"There's an average distance between particles, even though there is no ordering in the particles," said physics and chemical engineering professor Vinothan Manoharan in a Harvard news release. "It's that average distance that is important in determining the color."

Microcapsules manipulated to produce blue, green, and red structural colors.
Jin-Gyu Park Microcapsules manipulated to produce blue, green, and red structural colors.

Manoharan and his team see the potential for an entirely new paint technology based on the use of tunable color capsules. In addition to colorfastness, this paint is more environmentally friendly than traditional paints and dyes that contain toxic chemicals. The technology might also be used to create new kinds of electronic displays comprised of microcapsules rather than LEDs or liquid crystals.

"We think it could be possible to create a full-color display that won't fade over time," said Manoharan. "The dream is that you could have a piece of flexible plastic that you can put graphics on in full color and read in bright sunlight."

Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.