Ever wonder what colors the surface of oily rain puddles and soap bubbles? Those rainbows—also seen in peacock feathers and hummingbird wings—are called structural colors, and appear when light bounces around microscopic features on an object’s surface. But when scientists mimic this natural palette, they get colors that aren’t always fit for the runway: Structural colors are naturally iridescent, which means their shimmering tones can’t be used to create fixed pigments. Enter melanin, the naturally occurring molecule that gives your hair and skin its distinct colors. Researchers embedded a synthetic version of the molecule inside a special silica coating, adjusting the color by adjusting the thickness of the silica, and then submerged hundreds of these tiny particles in water. When they added oil, the water separated out, causing the balls to cluster together into microscopic “supraballs.” With the oil removed, the supraballs can be turned into powdered dyes that can be used like conventional pigments. But unlike conventional pigments, they don’t fade away in ultraviolet light, the researchers report today in Science Advances. What’s more, because melanin is biocompatible, these pigments could be used in more than just clothing and paint—they could one day transform the cosmetics and food industries.
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