The humble limpet has been receiving a lot of press lately, as scientists recently determined that the material from which its teeth are made is officially the world's strongest natural material. Now, an MIT/Harvard study suggests that a specific type of limpet's shell may hold the key to transparent displays that require no internal light source.
The mollusk in question is the blue-rayed limpet which, as its name implies, has bright blue stripes on its translucent shell. It is believed that these are used to make potential predators mistake it for a poisonous snail, which also has blue markings. The iridescent lines appear blue due to the fact that the shell material in those areas reflects the blue spectrum of incoming light, while absorbing other colors so that they don't drown out the blue.
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Some other animals' features, such as butterfly wings, also manipulate light in order to produce strikingly vivid reflected colors. Whereas they do so using organic structures such as scales, however, the blue-rayed limpet is reportedly the first known example of an organism doing so using inorganic mineralized structural components.
In order to determine how this is possible, the researchers used a combination of high-resolution 2D and 3D structural analysis to examine the nanostructure of the limpet's stripes.
What they discovered was that the top and bottom layers of the shell in those areas is fairly uniform, like the rest of the shell – it consists of densely-stacked calcium carbonate platelets and thin organic layers.
About 30 microns beneath the surface, however, the arrangement of those platelets changes into what is described as "a multilayered structure with regular spacing between calcium carbonate layers resembling a zigzag pattern." The spacing between the platelets in that structure is wider than elsewhere in the shell. Additionally, beneath that structure is a layer of randomly dispersed spheres.
The scientists discovered that due to its angle relative to the shell's surface, the zigzag structure is responsible for reflecting blue and green light. The spherical particles, on the other hand, absorb the other colors.
It is now hoped that a similar setup could be utilized in human technologies. These could include things like windows that remain mostly clear, but that also display text or other content in specific areas, by reflecting a given color of light instead of allowing it to pass through.
A paper on the research was recently published in the journal Nature Communications.