Bullet-fast shrimp club could lead to better body armor, airplanes and more

A mantis shrimp in one of UCR's tanks(Credit: University of California Riverside)

For a relatively small critter, the mantis shrimp certainly makes some major waves in the scientific community. The crustacean has served as the inspiration for research into everything from cancer-detecting camera technology to polarized lenses to strong and light composite materials. Adding to the body of knowledge in that last category is research out of the University of California Riverside (UCR) that has unravelled one of the secrets that helps the animal's claw move as fast as a .22 caliber bullet but not suffer any damage.

The secret, the scientists have discovered, lies with a herringbone pattern found in the outer layer of a fist-like appendage called a dactyl club the animal uses to pummel its prey. That club can go from 0 to 50 mph (80 km/h) in just three thousandths of a second, moving so fast that it boils the water in its path and creates a sonic shockwave that can stun or even kill small prey who happen to be having a very unlucky day nearby. At such speed, you'd imagine the club would have to be pretty tough – and it is.

Researchers at UCR had already decoded one part of the appendage responsible for its super strength. It had to do with spiral-shaped structures found at the innermost layers of the club's covering, which act as tiny shock absorbers. Now the researchers have turned their attention to the outer layer of the club – called the impact region – where they discovered the herringbone pattern.

"We knew from previous studies that the impact region allows the mantis shrimp to transfer incredible momentum to its prey while resisting fracture, but it was exciting to reveal through our research that the properties of this highly impact-resistant material are created by the novel herringbone structure," says Nicholas Yaraghi, a graduate student who led the current research, which was published May 30 in the journal Advanced Materials. Yaraghi also says that this is the first time such a pattern has been observed in the natural world.

To test out just how effective the herringbone pattern was, the UCR team worked with Pablo Zavattieri, associate professor of civil engineering at Purdue University who created first computer models and then 3D-printed versions of a material inspired by the design. They found that it was even more effective than the previously-discovered mantis shrimp coils in distributing physical stress and keeping the structure from cracking.

While the structure of the mantis shrimp's dactyl club has already led to the development of some next-gen composites, understanding the herringbone structure overlaid atop the shock-absorbing coils could help scientists develop even stronger materials such as better body armor, stronger aircraft hulls or better football helmets, says a UC Riverside report about the research.

"The smasher mantis shrimp has evolved this exceptionally strong and impact-resistant dactyl club for one primary purpose—to be able to eat," says professor David Kisailus, who's spent the last eight years at UCR uncovering ways the crustacean can inspire material design. "However, the more we learn about this tiny creature and its multi-layered structural designs, the more we realize how much it can help us as we design better planes, cars, sports equipment and armor."




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