Snails' Teeth: The Strongest Stuff in the Natural World

Despite the fame of diamonds as some of the Earth's toughest stuff, spider silk actually has long held the title as the strongest material in the natural world. That's because, if you think about it, it's pretty incredible how long strands of incredibly thin silk can not only withstand arachnids dancing upon them, but also the panicked thrashing of their prey. Nature World News even recently reported on Uloborus lace weavers that can craft "static spider silk" that's mere nanometers thick.

Now, however, even the lace weaver's silk is being dethroned. Researchers from the University of Portsmouth have discovered that limpets - small aquatic snail-like creatures with conical shells - boast teeth so strong that human industry is now looking to take inspiration from them for the next super-material.

"Until now we thought that spider silk was the strongest biological material because of its super-strength and potential applications in everything from bullet-proof vests to computer electronics," researcher Asa Barber said in a statement. "But now we have discovered that limpet teeth exhibit a strength that is potentially higher."

Barber recently led a study with his colleagues that looked into the molecular structure of limpet teeth. The results were published in the journal Interface of The Royal Society. (Scroll to read on...)

"Limpets need high strength teeth to rasp over rock surfaces and remove algae for feeding when the tide is in," Barber explained. "We discovered that the fibers of goethite (a mineral composite the teeth are made of) are just the right size to make up a resilient composite structure."

The researchers tested the teeth - which are actually found lining an unusual "tongue" of the snail - by scanning them and then trying to break them in various ways. This was particularly difficult given that the material was up to 100 times thinner than the average human hair.

Amazingly, the strength they calculated for the tooth material was, on average, about five gigapascals (GPa) - some five times greater than most spider silk. What's more, the researchers determined that the strength of these teeth would not vary with size, as the fiber structures were near-perfect.

"Generally a big structure has lots of flaws and can break more easily than a smaller structure, which has fewer flaws and is stronger," Barber added. "The problem is that most structures have to be fairly big so they're weaker than we would like. Limpet teeth break this rule."

The researcher compares the goethite tooth fibers to graphene - the scientific world's favorite carbon fiber material. This man-made material has countless beneficial applications, but it's only useful when laid down in flawless layers. The larger the material, the more likely a mistake will arise, and so scientists have been struggling to find ways to improve that layering process.

"With carbon fiber processing, they work very hard to take the flaws out of the fibers," Barber recently explained to BBC News. "But you could say, 'well, if I just make my fibers below a certain width, then maybe they wouldn't have to work so hard to get rid of the flaws.'"

He and his colleagues say that this is what makes the snail teeth a wonderful source of "bioinpsiration," as they provide a great example of that concept in action.

"Nature is a wonderful source of inspiration for structures that have excellent mechanical properties. All the things we observe around us, such as trees, the shells of sea creatures and the limpet teeth studied in this work, have evolved to be effective at what they do."

Why, they ask, would we not want to copy such perfection?

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