Limpet teeth strong enough to build planes, boats and racing cars

Limpet teeth are so strong they could be used to build airplanes, boats and even Formula 1 racing cars, say scientists. Limpet teeth are the strongest natural material we know of, they add, pushing spider silk into second place.

The researchers, from the University of Portsmouth, reported their findings in the academic journal Interface (citation below).

Limpets are small snail-like creatures that can be found in salt and fresh water. Most of them are seawater creatures.

At low tide, limpets clamp their shells tightly to rocks. At high tide they loosen their hold and wander about up to a distance of about 3 feet (1 metre) from their starting place. They scrape away at tiny seaweed and other algae with their tiny teeth. When the tide goes out they return to exactly the same spot and clamp on again.

A scanning electron microscope image of limpet teeth, made of the strongest natural material known to scientists. (Photo: University of Portsmouth)

The scientists used atomic force microscopy, which is over 1,000 times better than optical diffraction, to study the mechanical behavior of limpet teeth. Atomic force microscopes provide pictures of atoms on or in surfaces.

 

Professor Asa Barber, who works at the School of Engineering at the University of Portsmouth, said:

“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.”

“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 but now we have discovered that limpet teeth exhibit a strength that is potentially higher.”

Limpet teeth contain goethite

Study leader Prof. Barber and colleagues found that limpet teeth contain goethite, a dark or yellowish-brown mineral consisting of hydrated iron oxide. Goethite is the main component of bog iron ore and rust. It forms as the limpet grows.

Prof. Barber explained:

“Limpets need high strength teeth to rasp over rock surfaces and remove algae for feeding when the tide is in. We discovered that the fibres of goethite are just the right size to make up a resilient composite structure.”

The scientists say the fibrous structures of limpet teeth could probably be mimicked and used to make the hulls of airplanes and boats, as well as some high-performance engineering applications of racing cars.

Limpets on a rocky surface. Unlike barnacles and mussels, limpets move about when the tide goes down. (Image: Natural History Museum)

Prof Barber said:

“Engineers are always interested in making these structures stronger to improve their performance or lighter so they use less material.

Limpet teeth strength holds regardless of size

The team found that all limpet teeth have the same strength, no matter how large they are. Larger structures tend to have more flaws and are more likely to break than smaller ones.

The researchers used samples of material almost 100 times thinner than human hair, using a technique they had recently developed.

Prof. Barber said:

“The testing methods were important as we needed to break the limpet tooth. The whole tooth is slightly less than a millimetre long but is curved, so the strength is dependent on both the shape of the tooth and the material. We wanted to understand the material strength only so we had to cut out a smaller volume of material out of the curved tooth structure.”

“Biology is a great source of inspiration when designing new structures but with so many biological structures to consider, it can take time to discover which may be useful.”

Bioinspiration is the study of nature’s best designs and processes and then trying to imitate these systems and models to solve human problems.

Citation: “Extreme strength observed in limpet teeth,” Asa H. Barber , Dun Lu & Nicola M. Pugno. Interface. DOI: 10.1098/rsif.2014.1326 Published 18 February 2015.