Scientists now know why the blue, dotted stripes running along the shells of tiny mollusks called limpets light up, and say the mechanism behind it could someday be used as a platform for responsive, transparent displays.
A group of researchers from Harvard and MIT used high-resolution 2D and 3D scanning to investigate why the mollusk, found on the coasts of Norway, Iceland, Portugal, and the Canary Islands, flashes so brightly, even in murky waters.
They found the answer about 30 microns beneath the surface, in a unique, two-layer calcium carbonate structure that makes up the shell. The first layer has a regularly-spaced zigzag pattern, and the second a pattern of randomly-spaced spheres, causing blue light to be reflected and all other wavelengths of light absorbed.
The researchers said the structures could someday be replicated for transparent materials that require no internal light source.
"Let's imagine a window surface in a car where you obviously want to see the outside world as you're driving, but where you also can overlay the real world with an augmented reality that could involve projecting a map and other useful information on the world that exists on the other side of the windshield," Mathias Kolle, an assistant professor of mechanical engineering at MIT who co-authored the report said in a statement. "We believe that the limpet's approach to displaying color patterns in a translucent shell could serve as a starting point for developing such displays."
"It's all about multifunctional materials in nature."
Although birds, beetles, and other animals are able to produce similar colors, the limpet is the first known organism to create such an optical display using mineralized structural components rather than organic structures, like feathers.
According to the report, published in the journal Nature Communications, the structure is likely a defense mechanism evolved to make the limpet resemble other, more poisonous snails.
The limpet's shell structure could lend itself to engineering man-made optical displays particularly because its function doesn't overwhelm the shell's mechanical integrity.
"It's all about multifunctional materials in nature: Every organism, no matter if it has a shell, or skin, or feathers, interacts in various ways with the environment, and the materials with which it interfaces to the outside world frequently have to fulfill multiple functions simultaneously," Kolle said, according to the statement. "[Engineers] are more and more focusing on not only optimizing just one single property in a material or device, like a brighter screen or higher pixel density, but rather on satisfying several … design and performance criteria simultaneously. We can gain inspiration and insight from nature."