The United States military is apparently looking to shellfish for inspiration, as it develops the next generation of combat armor.

Researchers at the Massachusetts Institute of Technology, or, MIT, are currently testing a revolutionary type of transparent shielding for soldiers based on the structure of seashells, specifically those of the mollusk Placuna placenta, which are not only extremely resistant, but actually clear enough to read through.

At first glance, the shells of the sea creature seem an engineering paradox, being so strong and resilient when they are 99 percent calcite, generally known to be a weak, brittle mineral.

But in a recent study -- the findings of which are published online in the journal Nature Materials -- MIT graduate student Ling Li and professor Christine Ortiz explain they found the shells' extraordinary strength comes from a unique nanostructure that provides the shells efficient energy dissipation and the ability to localize deformations, along with optical clarity.

Ortiz, who serves as MIT's dean for graduate education, said in a news release she as dedicated much of her research to studying complex biological structures and properties of biological materials with the goal of creating better, synthetic versions of them.

In order to analyze the strength of the shells, which are mainly composed of calcite and about 1 percent organic material, the research team subjected samples to indentation tests, shooting a sharp diamond tip into the shells with a device capable of precisely measuring the loads that were delivered wkth each strike.

Afterward, the team used high-resolution analysis methods, such as electron microscopy and diffraction, to examine the damage that was left.

It was discovered that the shell material initially isolates damage with "twinning," an atomic-level process in which a crystal splits into a pair of mirror-image regions that share a common boundary -- like the wings of a butterfly.

This twinning process, the research found, occurs all around a stressed region, forming a boundary that keeps the damage from spreading outward.

The MIT team also discovered found twinning activates "a series of additional energy-dissipation mechanisms ... which preserve the mechanical and optical integrity of the surrounding material," Li said. The end result, she added, is a material ten times more efficient in dissipating energy than the pure mineral.

The properties of the natural armor have provided a template for both commercial and military applications that could include eye and face protection for troops, windows and windshields for combat and transport vehicles, and, of course, blast shields, Ortiz said.

The research was supported by the National Science Foundation, the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies, the National Security Science and Engineering Faculty Fellowships Program and the Office of the Assistant Secretary of Defense for Research and Engineering.