Limpet shells could provide the inspiration for a new generation of optical biomaterials. Bright blue lines within the structure of the mollusk shells are created through the interaction of a pair of optical structures newly-identified by researchers. These features, which run parallel to each other along the length of the shell, can reflect light, even in murky water.
Massachusetts Institute of Technology (MIT) and Harvard University researchers carefully examined the structure of the shells, in order to determine how the features glow so brightly under extremely low-light conditions.
The 3D nanoarchitecture of the animals was examined, using high-resolution 2D and 3D structural analysis. The top layer was found to be composed of platelets of calcium carbonate. Underneath this, the same substance is layered in a zig-zag pattern, just over spherical particles. The angle of the diagonal patterns are positioned so that they reflect the greatest amount of blue light, researchers discovered. Investigators found that the structures which produce the distinctive stripes reflect blue light, while absorbing all other colors.
The blue-rayed limpet is found in waters near Iceland, Norway, Portugal, the Canary Islands, and the United Kingdom, where the shellfish lives within kelp beds. Researchers believe that the blue stripes found in these limpet shells could assist the animals in resembling soft-bodied snails, which are poisonous to many predators.
The limpets are the first species known to exhibit colors through structures composed of inorganic minerals. Many other animals, including birds and insects (including butterflies) display brilliant colors, but they are biological features, such as scales or feathers.
New displays could be developed from similar structures, which would allow transparent displays that could be used in windshields and windows. These devices could be controlled so they could show maps, travel updates or other information, while still allowing drivers to easily see road conditions ahead of their vehicle.
"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 from MIT said.
Such a system would also require an internal light source, increasing the number of applications to which the new technology could be applied.
The blue stripes form in juvenile limpets, although dashed marks are common in the younger animals. The lines become more continuous as the limpet ages, and specific hues vary between individuals.
Analysis of the blue stripes in limpets was detailed in the journal Nature Communications.
