To humans, the mantis shrimp is known as the “thumb splitter,” due to its propensity to punch the digits of unfortunate fishers. To its prey on the seafloor, the mantis shrimp is known as “death incarnate”—the crustacean cocks back its two hammer-like appendages under its face, releasing them with such force that they obliterate clam shells , one of the toughest materials in nature. The mantis shrimp has even more fun with crabs, strategically blowing off their claws first so the prey can’t defend itself.
All that bashing puts serious stress on the hammers themselves. So to deal with the constant punching, evolution gave the material of these weapons a “Bouligand” shape. Instead of the layers of material neatly stacking one on top of another, the layers are twisted, almost like the helical structure of DNA. So when a mantis shrimp’s hammer smashes into a thumb or a clam or a crab’s face, any crack in its structure will propagate in a twist pattern, dissipating the energy throughout the material. As a result, the hammer doesn’t snap in half.
Neat, said engineers at the University of Southern California and the University of California, Irvine, who’ve invented a clever kind of material based on the mantis shrimp’s clobber-sticks. (If you’re one for formality, they’re technically known as dactyls.) It’s a twist within a twist: They’ve been able to get minerals to grow within a 3D-printed shrimp-inspired Bouligand structure with the help of bacteria, of all things.The researchers began by 3D printing a simple lattice structure, basically a grid, out of a polymer. As you can see in the image above, the resulting scaffold had plenty of empty space within—think of it as being like the beams that support a building. They then dipped the whole structure in a bacterial solution and let it sit for 12 to 24 hours. The Sporosarcina pasteurii bacteria within the solution attached to the polymer lattice and started secreting an enzyme called urease.