The iridescent blue-green stripes found on the translucent shell of the blue-ray limpet may lead to responsive, transparent displays. Credit: M. Kolle / MIT
The striking blue-green iridescent patterns of a tiny mollusk’s shell have inspired researchers at the Massachusetts Institute of Technology (MIT; Cambridge, Mass., USA) to uncover the optical cause of its appearance and find potential uses for its natural design (Nat. Comm., doi: 10.1038/ncomms7322). Stefan Kolle, a marine biologist at Harvard University in Cambridge noticed the brilliant patterning on the shell of the blue-rayed limpet, Patella pellucida, a tiny kelp-bed mollusk found in the eastern Atlantic, which flashes brightly even in murky water. He recruited his brother, Mathias Kolle, assistant professor in the department of mechanical engineering at MIT, to investigate the source of the bright dashed lines.
Mathias, whose work is focused on bio-inspired technology, and colleagues at MIT scanned the surface of the limpet’s translucent shell with a scanning electron microscope, a spectroscope and a diffraction microscope. Then they applied 2-D and 3-D structural analysis to find that the stripes are a result of a 3-D nano-architecture beneath the shell’s surface. At a depth of 30 microns, the calcium carbonate plate morphs into a multilayered zigzag pattern, on top of a layer of randomly spaced spherical particles. While the zigzag pattern reflects only blue and green light, the layer of disordered particles absorbs the other wavelengths, making the stripes even bluer.
The group speculates that the stripe patterns and color may act to mimic other distasteful organisms in the limpet’s habitat. Researchers could someday use the naturally evolved design as a starting point to engineer advanced transparent optical displays, such as augmented reality gaming goggles or a projected map onto a vehicle window.