The incredible hammer of “mantis shrimp”

This is one of the fastest movements of nature: the blow of the mantis shrimp to break the shells. This hammer also of interest to researchers in search of lightweight and durable materials.

Image via St. Louis Marine Solutions

The Rocky Balboa of the Indo-Pacific Ocean

When the multicolored squill drops it’s knock against the shell of a snail, it is as if it was shooting with a .22-caliber bullet. The force of impact is more than 1000 times the weight of the squill. This shellfish, nicknamed “mantis shrimp” because of the shape of its appendix, broken shells for food without damaging the hammer, measuring only a few millimeters long. Such a force coupled with a high capacity for resistance has sharpened the curiosity of David Kisailus (Unievrsity Purdue, USA) and colleagues, who took the stomatopod’s hammer under a microscope to discover its secrets.

Three layers of different materials

Curiously, the part of the hammer which strikes the shell consists mainly of mineral hydroxyapatite, a mineral found in teeth or bones of vertebrates.

Almost more important than the make-up of the arm is the design of it: it has a spiral shape, akin to the shape of DNA, that absorbs shocks. Since the mantis shrimp molts, it only needs to last until it’s replaced.

“Because the fibres are arranged in this helicoidal architecture, those cracks will have to propagate a very long distance to escape the club – and they never do,” Kisailus said.

It’s not all: behind this facade lies a second layer of chitosan fibers reinforced with a material rich in magnesium, forcing cracks to change direction constantly. What makes a good resistance to the material. A third and final layer surrounds the area absorbs shock, from consolidating the hammer.

Towards new armor?

The researchers, who publish their work in the journal Science June 8, 2012, plan to draw the hammer in mantis shrimp (Odontodactylus Scyllarus) to develop new protective materials, light and strong. The primary stakeholders are the research services of the army: Kisailus and his colleagues received 590,000 dollars (465,000 euros) from the U.S. Air Force to continue work on the squill and imitate its properties!

Tagged Aquatic life, David Kisailu, fastest movements of nature, hammer, mantis shrimp