Sea Urchin Cousin May Hold the Secret to New, Super Strong and Lightweight Materials

A sea urchin, of all animals, has spurred an idea for new, lightweight materials. Scientists have taken a closer look at a sea urchin cousin, known as the heart urchin, as the inspiration for strong, lightweight materials.

Heart urchins are also known as sea potatoes and measure up to 5 cm in diameter. They're heart-shaped, burrow in sand, and extend a channel to feed on organic particles from the waters above their burrow. Like "regular" sea urchins, these heart urchins are soft creatures that use their calcium carbonate exoskeletons to protect their otherwise edible bodies from predations. It's these shells that scientists examined a bit more closely.

In order to understand the sturdy calcium carbon shells, the researchers used x-ray microtomography. This technique was used to create 3D images of the material contents, without having to break the shells into pieces. The ultra fine resolution allowed researchers to understand the shell's strength.

Heart urchin shells actually consist of more air than chalk. In fact, the material resembles soapsuds; it consists of an incredible number of microscopic cavities held together with slender calcium carbonate (chalk) struts. However, these struts are about six times stronger than chalk.

The structure actually nears a theoretical ideal for foam structure strength.

"We found an example of a surprisingly simple construction principle," said Dirk Muter, one of the researchers, in a news release. "This is an easy way to build materials. It allows for great variation in structure and strength. And it is very near optimal from a mechanical perspective."

The findings are published in the journal Acta Biomaterialia.

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