Structures inside the shell of the blue-rayed limpet give the mollusk its striped appearance and cause its shell to flash brilliantly, but the feature could also help scientists develop groundbreaking transparent displays.
These structures were found to be configured to reflect blue light while absorbing light of other wavelengths, allowing the mollusk's shell to mimic poisonous soft-bodied snails and ward off predators, MIT reported. This is the first evidence of any organism in nature using mineralized structural components to produce optical displays. This stunning adaptation could act as a guide in helping scientists design "color-selective, controllable, transparent displays" that would not require an internal light source and could be built into windows and other glass objects.
"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," said co-author Mathias Kolle, an assistant professor of mechanical engineering at MIT. "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."
A team of researchers performed a detailed structural and optical analysis of the limpet shells using scanning electron microscopy, and found there was no structural different between striped and non-striped areas of the shell's surface. The team then used a combination of high-resolution 2-D and 3-D structural analysis to uncover the 3-D nanoarchitecture of the photonic structures deep within the shell.
The analysis revealed that 30 microns beneath the shell surface in the blue striped regions, the generally uniform plates of calcium carbonate transformed into two distinct features: "a multilayered structure with regular spacing between calcium carbonate layers resembling a zigzag pattern, and beneath this, a layer of randomly dispersed, spherical particles," the researchers reported.
Using optical microscopy, spectroscopy, and diffraction microscopy to assess the light-reflection properties of the blue stripes, the researchers determined the structures were developed to reflect blue and green light. The zigzag pattern is believed to act as a filter by reflecting only blue light and making the stripes appear even more brilliantly-colored. The group's findings on the shell's fascinating optical properties could be incorporated into the design of new and improved optical displays.
"[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," Kolle concluded.
The findings were published in a recent edition of the journal Nature Communications.
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