Snail's iron armour eyed by military
The iron-encrusted shell of a snail that lives near deep-sea volcanic vents could inspire better armour for soldiers and vehicles, researchers say.
The scaly-foot snail, discovered in 2003 near hydrothermal jets on the floor of the Indian Ocean, has a unique three-layered shell that withstands forces that would break other snail shells.
Materials scientist Christine Ortiz of the Massachusetts Institute of Technology and her colleagues examined the small-scale properties of the shell and created a computer simulation to examine how the armour works.
Ortiz said the research could help scientists and engineers design better military armour. Ortiz is a member of MIT's Institute for Soldier Nanotechnologies and her research was funded in part by the U.S. Army and Department of Defence.
In its natural environment near undersea volcanic vents, the scaly-foot snail faces high temperatures, rapid changes in temperature, high acidity and attacks from predators such as crabs.
The crabs will pick up a snail in its claws and squeeze it — for days if needed — until it breaks. The snail appears to have adapted to resist this kind of attack.
The outer layer of the snail's shell is composed of iron sulphides. The scaly-foot snail is the only known animal species that uses iron sulphides as part of its structure.
The middle layer is organic and much thicker than the other two. The researchers compare it to the thin protein coating, called the periostracum, seen on the shells of other snail species. The inner layer is composed of aragonite, a calcium mineral found in mollusk shells and corals.
The researchers in Ortiz's lab used a device called an indenter that steadily applied a force to the shell using a diamond tip. The scientists could measure the force and observe the displacement in the shell to determine its mechanical properties.
They found that each of the layers contributes differently to the armour's effectiveness. The middle protein layer appears to absorb the mechanical energy of a squeezing attack, as well as dissipating heat.
Ortiz and her colleagues plan on further research into the nanomechanical properties of natural shells, including those of chitons, urchins, beetles and armoured fish.
Their work was published this week in the Proceedings of the National Academy of Sciences.