The Harlequin (or Peacock) Mantis Shrimp has the fastest recorded punch of any living animal (over 50mph!) – it can even smash through the glass in aquarium tanks. In fact, the shrimp’s tough little claws have a much higher specific strength and toughness than any synthetic composite material – and US scientists believe it could lead to stronger body armor.
The shrimp is one of the toughest creatures in the natural world. While it is only 3–18 cm in length, the shrimp is capable of moving its clubs to reach speeds in excess of 80 km per hour, allowing it to deliver an instantaneous force of more than 700 N. This is strong enough to bash through the outer shell of any crustacean. For years, scientists have been simultaneously baffled and intrigued by this tough little shellfish, but now they believe they have found the answer. Not just that, but with some ingenious bio-mimicry, the shrimp’s claws could have real world benefits for soldiers and law enforcement officers.
When the shrimp’s claws hit an object, air bubbles are trapped between the club and the creature’s shell which cause them to collapse to create regions of great local stress. What is astounding is that this process can be repeated thousands of times without any apparent damage to the club, which is eventually replaced in a moulting process.
A partnership between Harvard University, the University of California and the Nanyang Technological University in Singapore used electron microscopy, X-ray microtomography, synchrotron X-ray diffraction and energy-dispersive X-ray spectroscopy to inspect the shrimp’s club. What they found was surprising.
The club is made from a layer of very hard crystalline calcium-phosphate ceramic material, known as hydroxyapatite, that is about 60 µm thick. It is actually quite fragile and would shatter on impact if it was working on its own, but the team discovered a much thicker region beneath it comprising layers of fibers made from the polysaccharide chitosan – an elastic material often found in seafish exoskeletons.
Due to the multiple layers of fibers (also known as a “helicoidal” structure), the team believe that the club is prevented from fracturing as any crack would be forced to change direction in the elastic layers. The absorbent nature of the the elastic modulus also served to take off some of the impact energy and reflect it back towards the surface as the club structure an object.
With this design in mind, the team believe that body armor could be designed in a similar way, using composites of hard ceramic and elastic organic materials. Who would have thought something so small could be so tough?
via Physics World