By Ryan Whitwam Feb. 18, 2015
The limpet is not a terribly interesting organism on the surface. This group of aquatic snails live their lives inching along rocks, scraping off algae for food. The way they scrape those rocks clean is actually getting a lot of interest in scientific circles, though. Limpet teeth have recently been tested by researchers at the University of Portsmouth and found to be the hardest biological material in the world.
These teeth aren’t like the teeth we humans have. They are protein-mineral composites that cover the snail’s tongue (called a radula). These structures have to be sturdy because they are essentially being raked across rocks all day as the snail uses them to free up algae to eat. The key to its strength, according to the researchers, is the tightly packed mineral fibers consisting of a iron-based substance called goethite. These goethite fibers are interlaced with a protein scaffolding in the same way carbon fiber can be combined with plastics to increase their strength.

To test the strength of limpet teeth, the team started with tiny fragments and shaved them down to a microscopic dog-bone shape. These fragments were then glued to an atomic force microscope that could gauge how strong the material was. The calculated strength of limpet tooth material was five gigapascals, about five times better than the previous front runner, spider silk. Even the outliers among spiders fall short of limpet teeth.
Compared to man-made materials, limpet teeth are better than kevlar and almost as good as the strongest carbon fiber composites. Taking what they’ve learned from the structure of limpet teeth could help make the composites used in body armor and aircraft hulls more durable and lighter. It may also be easier to replicate than spider silk, which has been notoriously tricky.
This could be a big deal in materials science, and we have an unassuming little mollusk to thank for
