What’s in a mollusk? Maybe the secret to a new generation of screens

The blue-ray limpet puts on quite the light show. (Image: Mathias Kolle / MIT)
The blue-ray limpet puts on quite the light show. (Image: Mathias Kolle / MIT)

A mollusk, marked by the brilliant pattern of its shell, is inspiring engineers to design an advanced screen that would, for example, allow drivers to overlay navigation information on their car windshield — without blocking their view of the road.

The mollusk is a blue-ray limpet, which lives on the rocky coast of Wales and displays blue stripes that only appear when light strikes the translucent shell at certain angles. If researchers can duplicate its trick of changing appearance under different lighting, it could spur a new generation of so-called augmented reality screens that display information as users look through them, such as window that displays the temperature outside.

“If we have a transparent screen, you may want to see the world on the other side, but you may want to project information on that screen,” said Mathias Kolle, a professor of mechanical engineering at MIT. ““When you drive you want to see what’s around you, but you may want to display a map or other information to make navigation easier.”

Kolle is part of the team of researcher at MIT and Harvard University who have discovered the arrangement of minerals in the blue-ray limpet’s shell that allows it to put on its light show. The researchers believe the animals evolved these features to mimic the markings of certain species of poisonous snails, and fool predators into skipping them as lunch.

Kolle, who has made a career of studying the magical materials of plants and animals, said the blue-ray limpet’s secret is the way the molecules of the calcium carbonate in the shell are stacked. (Calcium carbonate is the mineral found in limestone). Those molecules are arranged in such a way that they divert wavelengths of light to reflect blue light.

Kolle and his team found that if the stack of calcium carbonate molecules is thicker, or the spacing between the layers changes, the color of the stripe changes, too. That suggests that rearranging thickness and spacing of materials can create dynamic screens to display different types of information with, say, a tilt of the head, rather than a strike of a key or touch of a screen.

The MIT and Harvard researchers reported their findings in the Thursday issue of the journal Nature Communications.

The team has years of experience copying nature’s tricks. Last year, Kolle demonstrated how the patterning on butterfly wings could be printed on a bank note to provide an anti-counterfeit feature that is almost impossible to replicate.

Another member of the team, Harvard professor Joanna Aizenberg, has made a speciality of repurposing natural materials for human uses. Her company SLIPS Technologies is developing ultra-slippery coatings, modeled on the insides of pitcher plans, to repel blood and bacteria. Christine Ortiz, of MIT, has received federal funding to reverse-engineer the tough-as-armor architecture of a sea snail to create protective suits for soldiers.

Nidhi Subbaraman writes about science and research. Email her at nidhi.subbaraman@globe.com.
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