Unique three-layered snail shell could lead to tougher body armor
February 1, 2010
They say life imitates art, but any scientist knows that the best designs imitate life. Researchers from the MIT Institute for Soldier Nanotechnologies (ISN) are drawing new biomimicry inspiration for body armor design from a hardy ocean snail that boasts a shell structure unlike anything else seen in nature... or in material research labs.
Introducing Trochus niloticusDiscovered in 2003 around the hostile hydrothermal vents of the Indian Ocean, and drawing immediate interest from Professor Christine Ortez of MIT's Laboratory, this particular hot vent gastropod, the Trochus niloticus or more quirkily-named "scaly-foot" snail has been found to demonstrate a structural shell unlike any other naturally-occurring or synthesized armor. It is formed from three layers comprising an outer layer fortified with iron sulfide granules, a thick organic middle layer, and a calcified inner layer. Conversely, most other snail shells have a calcified layer with a thin organic coating on the outside.
How they discovered it...In the new paper, partly funded by the Army and the Department of Defense, Ortiz and her colleagues measured the mechanical properties of the shell by subjecting it at a nanoscale to pressure applied with a diamond-tipped machine called an "indenter". The results suggest that the unusual organic middle layer absorbs a lot of energy allowing the shell to dissipate mechanical energy, and also heat and thermal fluctuations that would fracture weaker shells.
So what does that mean for the snail?Put simply, the super shell protects against hostile attack from crabs and other snail species, and also dissipates the fluctuations in temperature and acidity in the harsh habitat it favors. Since crabs may subject a shell to sustained mechanical pressure for days in the quest for a tasty escargot, the heroic capacity to resist persecution is a welcome advantage.
... and for future body armor design?Ortiz, a material scientist and a member of MIT's ISN, is studying a number of other natural armor systems in urchins, chitins, beetles and armored fish to understand the fundamental design principles of their exoskeletons.
She thinks research in this field may help engineers design improved body armor systems for humans in perilous situations, like the military or police. Additionally, she proposes that replacing weaker parts of an armor system with stronger materials could yield much tougher composites for use in armor or structural applications like automobile panels or plane wings.
She knows that nature has a lot to teach us in the art of defense.