It may be time to ditch the Spinal Tap jokes and start dropping Iron Butterfly references when it comes to talking about the world's blackest-black materials.
Duke University doctoral student Alex Davis conducted a study on ultra-dark butterflies that could lead to new innovations in super-dark coatings. These coatings, the most famous of which is known as Vantablack, are used for everything from telescopes to art projects.
But ultra-black butterflies like Rajah Brooke's birdwing butterfly give human-made coatings like Vantablack some serious competition. "As little as 0.06% of the light that hits them is reflected back to the eye," Duke said in a release on Tuesday.
What makes this phenomenon so intriguing is the light weight and thinness of the butterflies' natural coloration. Davis and colleagues used an electron microscope to take a super-close-up look at how the insects achieve this feat.
Zooming in on a butterfly wing reveals layers of scales. As for the ultra-black appearance, Duke described it as "an optical illusion created by the 3D structure of the butterflies' wing scales."
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Microscope images highlight the details of these nanostructures, which appear as a series of ridges with honeycomb-like formations in between. The researchers discovered these "ridges and pillars are deeper and thicker in ultra-black scales compared to 'normal' black scales."
The butterfly scales aren't as black as Vantablack or similar coatings, but the paper noted they are thinner and can be fabricated at lower temperatures. The study calls for further research into the viability of turning this biological wonder into a synthetic material.
The butterflies scrutinized in the study use black as a key part of their wing color schemes. Bright patches ranging from blue to green to red pop out against the ultra-dark backgrounds.
While scientists are fascinated by the potential for these nanostructures, the butterflies themselves might just be looking for a good time. "We think it's likely some sort of signal to mates or maybe a predator. But there's a host of other possibilities, and we're hoping to clear that up," said Davis.