The mantis shrimp, one of the ocean's most ornery creatures, can take on attacks from its own species without injury. During ritualised fighting, the shrimp uses a shield-like segment of abdominal armour called the telson to defend itself. Engineers have discovered how the telson can absorb the blows from its own species.
The shrimp’s strategy could solve a big manufacturing problem: Creating lighter materials that absorb a lot of energy from a sharp impact within a limited amount of space. What if there was a material that could prevent a car roof from caving in on passengers during an accident, or fragile objects from breaking when transported over long distances? Applications could also extend to protective gear, where there is a need for lightweight graded composite materials with potential flexibility and multi-functionality, as well as improved damage tolerance.
The research work, published in the journal Advanced Functional Materials, was performed by a team of researchers at the University of California (UC), Riverside and Purdue University in the US.
A telson can be shaped either as a territorial shield for ‘smasher’ species or as a burrowing shovel for ‘spearer’ species that also stabs prey. The researchers found out how the telson of the smasher, compared with that of the spearer, is better at protecting the mantis.
Their findings reveal that the smasher telson has curved ridges called carinae on the outside and a helicoidal structure shaped like a spiral staircase on the inside. Researchers at UC Riverside ran tests on both the mantis shrimp itself and 3D-printed replicas of the telson, showing that the carinae and the helicoidal structure, which prevents cracks from growing upon impact, both stiffen the smasher species’ shield and allow it to flex inward. The shield then absorbs significant amounts of energy during a strike without falling apart.
The mantis shrimp can fight without getting injured. Researchers are mimicking the tail segment structures that make this possible (image: University of California, Berkeley image/Roy Caldwell)
"The smasher shield is clearly more ideal for preventing impact from reaching the rest of the body, which makes sense because the mantis has organs all the way to its tail," says Pablo Zavattieri of Purdue University. They also observed that the speed of the smasher’s attacking dactyl club – which attacks the telson shield – was that of a 0.22 calibre bullet.
Zavattieri's team has already begun incorporating the crack propagation mechanisms of arthropod exoskeletons into 3D-printed cement paste, a key ingredient of the concrete and mortar used to build various elements of infrastructure.
But there are still more clues to uncover about all that the shrimps’ structures have to offer, the researchers say, as well as how to manufacture them into new materials. "The dactyl club is bulky, while the telson is very lightweight. How do we make protective layers, thin films and coatings for example, that are both stronger and lighter?" Zavattieri said.
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Thumbnail image: Olena Kryvorichko / 123rf