Personal protection equipmentMantis shrimp could inspire new body, vehicle armor

The Mantis shrimp inspires a new approach to armor // Source: aquarium4u.gr

Military body armor and vehicle and aircraft frames could be transformed by incorporating the unique structure of the club-like arm of a crustacean that looks like an armored caterpillar, according to findings by a team of researchers at the University of California, Riverside’s Bourns College of Engineering and elsewhere published online today, June 7, in the journal Science.

A University of California-Riverside release reports that the bright orange fist-like club of the mantis shrimp, or stomatopod, a 4-inch long crustacean found in tropical waters, accelerates underwater faster than a 22-caliber bullet. Repeated blows can destroy mollusk shells and crab exoskeletons, both of which have been studied for decades for their impact-resistant qualities.

The power of the mantis shrimp is exciting, but David Kisailus, an assistant professor at the Bourns College of Engineering, and his collaborators, were interested in what enabled the club to withstand 50,000 high-velocity strikes on prey during its lifespan. Essentially, how does something withstand 50,000 bullet impacts?

They found that the club is a highly complex structure, comprising three specialized regions that work together to create a structure tougher than many engineered ceramics.

The first region, located at the impacting surface of the club, contains a high concentration of mineral, similar to that found in human bone, which supports the impact when the mantis shrimp strikes prey. Further inside, highly organized and rotated layers of chitin (a complex sugar) fibers dispersed in mineral act as a shock absorber, absorbing energy as stress waves pass through the club. Finally, the club is encapsulated on its sides by oriented chitin fibers, which wrap around the club, keeping it intact during these high velocity impacts.

“This club is stiff, yet it’s light-weight and tough, making it incredibly impact tolerant and interestingly, shock resistant,” Kisailus said. “That’s the holy grail for materials engineers.”

Kisailus said the potential applications in structural materials are widespread because the final product could be lighter weight and more impact resistant than existing products.

For example, with electric cars less weight will reduce power consumption and increase driving range. With airplanes, less weight would reduce fuel costs and better impact resistance would improve reliability and cut repair bills.

Kisailus, however, is primarily focused on improving military body armor, which can add thirty pounds to a service member’s load. His goal is to develop a material that is one-third the weight and thickness of existing body armor.

Kisailus and James C. Weaver, who worked with Kisailus as a post-doctoral scholar and is now at Harvard University, began work on the mantis shrimp when Kisailus arrived at UC Riverside in 2007.

They were later joined at UC Riverside by Garrett W. Milliron, a Ph.D. student, and Steven Herrera, an undergraduate student.

Kisailus, who studies the structures of marine animals for inspiration to develop new materials, has also worked with snails such as the abalone and chiton, as well as sea urchin.

Those animals were all studied for their defensive prowess, in other words their exterior protection from predators. The club of the mantis shrimp interested Kisailus because it is an offensive tool.

“We have been studying these other organisms when we should have been studying this guy because he literally eats them for breakfast,” Kisailus said.

The force created by the mantis shrimp’s impact is more than 1,000 times its own weight. It is so powerful that Kisay characterization gave us multiple views of the same problem, making it a very thorough investigation,” Kisailus said.

— Read more in James C. Weaver et al., “The Stomatopod Dactyl Club: A Formidable Damage-Tolerant Biological Hammer,” Science 336, no. 60868 (7 June 2012): 1275-80 (DOI: 10.1126/science.1218764)