Sea mollusks often face attack by crabs and have developed a natural defense system. In order to study how this system works, Ortiz first accessed the mechanical qualities of the shell. This was achieved by slowly pushing a diamond tipped probe through the shell of a mollusk, using a force equivalent to an attacking crab’s claw.

The chiton shells are comprised of three layers, each of which posses a unique and crucial quality. The outermost layer consists of iron sulphide particles, measuring about 20 nanometers across. These particles are held together by a pliable organic matrix produced by the mollusk. This exterior layer is designed to absorb impact induced energy by propagating “micro-cracks” throughout the material, and thereby preventing larger crack formation.

The middle layer of the shell is thick, spongy, and designed to dissipate remaining energy from an attacker’s blow. This layer is crucial in protecting the innermost layer of the shell, which is made of calcium carbonate, and is very brittle.

While several systems employ similar technologies (i.e. the multi-layering  in helmets), Ortiz states that the idea of using a iron-based nano-particle coating is “largely unexplored, and particularly promising.” More on Christine Ortiz and her work can be found here, at her group website.