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For the first time, scientists have identified the tiny differences that give a group of butterflies their unusual iridescent colors.

Papilio butterfly
photo: Optical Materials Express

Look closely at many butterflies’ wings, and you’ll notice a dense, repeating pattern of tiny structures, or crystals, that reflect light in unusual ways. Scientists are interested in replicating butterfly wing crystals to give interesting color properties to manmade objects. They may even be able to create color-changing objects, thanks in part to new research out of Hong Kong Baptist University.

Researchers led by physicist Kok Wai Cheah focused on three swallowtail butterflies from a genus known as Papilio. The butterflies are all differing shades of green when viewed from above but blue when viewed from the side.

Papilio butterflies

To pinpoint how the butterflies change color based on the viewing angle, the researchers took a look under a microscope. They found the wings are built from alternating layers of solid material and empty space filled with pillars of the solid material. The structure makes the wings act as a mirror that reflects certain wavelengths of light, or color, that change depending on the viewing angle.

They then found the color is determined by how many layers the wings hold; one butterfly had seven layers of the solid material, while another had eight. The thickness of each layer also influenced the color.

Butterfly wing nanostructures

If scientists are able to replicate the findings, they could develop electronics, paint, clothing and beyond that do not require any sort of pigment. Instead, the color comes from light. The Hong Kong Baptist University team’s research could allow them to engineer precise color combinations.

“You would just tune your structure to produce the color you want,” Cheah said in a release. They published their findings today in the Optics Materials Express journal.

Butterfly wings have been studied for years. Understanding their properties could also lead to better semiconductor devices suited to electronic circuitry and solar cells. In 2008, Penn State scientists developed a mold from a butterfly wing, but couldn’t produce structural replicas fast or accurately enough.

“It was very exciting to see how nature can create a nanostructure that’s not easy to replicate by humans,” Cheah said in the release.

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  1. This seems really incredible to me, that we can change colors just by making really small ridges or whatever. Hopefully we’ll get more than color changing shirts out of this though

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