These weird sea creatures inspire body armor with built-in optics

A team of MIT researchers are drawing inspiration from a type of aquatic creatures known as chitons—who have miniature eyes embedded directly in their hard protective shells—to develop new body armor with built-in optics that could be used to monitor surroundings.

MIT professor Christine Ortiz, as well as colleagues from the Cambridge, Massachusetts-based institute, Harvard University and elsewhere, reported in the latest edition of the journal Science that the chiton Acanthopleura granulata possesses “an integrated sensory system” that “includes hundreds of eyes with aragonite-based lenses,” providing both sight and protection.

These ceramic-plated eyes, the authors explained in a statement, could potentially be adapted to protective gear for soldiers or individuals working in hazardous environments. During a series of experiments, the researchers demonstrated that the chitons’ eyes are functional enough to form a focused image, allowing it to monitor its environment without sacrificing their safety.

The rest of Acanthopleura granulata’s shell is opaque, MIT graduate and Harvard postdoc Ling Li noted. Only the eyes are transparent, and through the use of high-resolution X-ray tomography and theoretical models, the team was able to discover that they are capable of focusing light and forming images in the photoreceptive chamber both in the water and in the air.

Not too small to form images after all

Chitons, which are about the size of a potato chip, tend to be more flexible than other mollusks due to the fact that their shells are comprised of eight separate plates overlapping each other, the MIT researchers explained. They live in the intertidal zone—meaning that they can be underwater or exposed to the air at different times—and can be found in many parts of the world.

Using equipment located at Argonne National Laboratory in Illinois, Ortiz, Li, and their fellow scientists examined the 3D architecture of the creatures’ eyes, which are less than one-tenth of millimeter in diameter. They also used material characterization techniques to figure out the size and the orientation of the crystalline grains that make up their lenses—something that Li said is essential to better understanding their optical capabilities.

They were able to successfully demonstrate for the first time that these tiny eyes were capable of forming focuses images and were not merely basic photoreceptive units. While some experts had believed that the eyes were too small and that such a tiny lens would be unable to form an image, the MIT team said that they were able to isolate some of them and prove otherwise.

Their findings could eventually result in the development of biologically-inspired materials that could provide both physical protection and optical visibility simultaneously, Li said. Peter Fratzl, a professor of biomaterials at the Max Planck Institute of Colloids and Interfaces not involved in the work, said that the eyes were “a truly impressive example of a multifunctional material.”

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Feature Image: MIT researchers