Sep 17, 2017

Many colors that don't fade, made from one pigment

Five different pigments made from supraballs. Photo: Ming Xiao / University of Akron

Scientists at the University of Akron in Ohio have developed a way to use a single pigment — melanin — to create a range of usable colors, reports Science News. In a paper published September 15 in Science, the authors explain how melanin can be bound into "supraballs" to create the colors of the rainbow.

Why it matters: Traditional chemical pigments lose their color as they break down so for years researchers have tried to make longer-lasting colors. The new pigments — similar to those found in bird feathers and elsewhere in nature — could be added to paints, plastics, inks and other products.

How they did it: The supraballs were made by coating nanoparticles of melanin, the same pigment that colors human skin, in a silica shell and bundling them together. By varying the thickness of the shell the researchers could change the density of the melanin and create a variety of colors. This process shows promise because it's fairly simple to create. The supraballs naturally form when the nanoparticles are added to a room-temperature mix of water and alcohol.

How it works: Sort of the same way some eye colors work. Blue and brown eyes both contain the same brown melanin used in this study. But blue eyes have less of it, so the the light scatters differently and makes them appear blue. This scattering, called the Tyndall effect, is the same reason the sky is blue. It's also why discarded bluejay feathers seem to lose their color if you rough them up a bit: the structure that reflects the light and makes blue is disrupted.

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