Mantis shrimp may hold the secret to lighter, tougher body armors
June 9, 2012
The mantis shrimp is a fascinating creature that has the ability to punch its prey into submission with a club that accelerates underwater at around 10,400 g (102,000 m/s2). By studying the secrets behind this formidable weapon, a Californian researcher hopes to develop an innovative, hi-tech material that is one third the weight and thickness of existing body armor.
Some animals are very poorly named: the flying lemur can't fly and is not a lemur, the rabid wolf spider is as placid and innocuous as spiders come, and the jackass penguin gets along just fine with its peers.
The mantis shrimp fits in this category - it is neither a mantis nor a shrimp. It lives a solitary life, displays very aggressive behavior, and, most importantly, packs a mean punch. So mean, in fact, that its "fist" can go from 0 to 50 mph (0 to 80 km/h) in just three thousands of a second, underwater. As it accelerates the club creates a pressure wave so strong that it instantly boils the water in front of it and even generates tiny flashes of light before striking its target with the force of a speeding bullet.
The animal needs to be kept in special aquariums so it won't break the glass. This video gives a sense for just how powerful its strike can be.
The mantis shrimp uses its formidable weapon to break the shells of its prey but, until recently, it was unclear how its club could receive such a severe, repetitive pounding without suffering too much damage. The club, in fact, handles as many as fifty thousands strikes during its lifespan. So how does it maintain structural integrity? Assistant professor David Kisailus from the University of California, Riverside set out to find an answer.
The club, Kisailus found, is a highly complex structure comprised of three highly specialized regions working together to create a structure tougher than many engineered ceramics.
The impact area is one millimeter thick and contains a high concentration of mineral similar to that found in human bone, except that the crystals that compose it are aligned perpendicularly to the surface of the strike to minimize cracks.
Further inside, highly organized layers of chitin fibers act as shock absorbers. The fibers are arranged in a helical structure to slow down the spreading of cracks. Here's the trick: the helix forces the cracks to constantly change direction, which disperses their energy and quickly stops them from propagating.
Finally, the club is encapsulated on its sides by chitin fibers that wrap around the club, keeping it intact – much like a boxer who places tape around their fists.
A comprehensive study of the nature of the microscopic structure of the mantis shrimp's club appeared in a recent issue of the journal Science.
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