Engineers discover strongest natural material

Researchers from the University of Portsmouth have discovered that limpet teeth – small structures on the aquatic snail’s tongue used to scrape algae off rocks – have the highest tensile strength of any biological material yet discovered. Mimicking their structure, the researchers say, could lead to stronger and lighter composite materials.

“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,” said University of Portsmouth mechanical engineering professor, Asa Barber, who led the study.

According to the research, recently published in Royal Society journal Interface, the limpet tooth samples tested displayed tensile strength ranging from 3.0 to 6.5 GPa, with an elastic modulus (stiffness) of 120 ± 30 GPa. By comparison, the tensile strength and elastic modulus of spider silk typically ranges up to 4.5 and 10 GPa, respectively. In addition, the study found that the tooth material retained its strength properties independent of the sample size.

“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 said. “The problem is that most structures have to be fairly big so they’re weaker than we would like. Limpet teeth break this rule as their strength is the same no matter what the size.”

On par with some of the most durable man-made fibres, the limpet tooth owes its unique strength to its composite structure. The teeth are composed of chitin, a biological polymer, reinforced by a large number of nanofibres composed of the mineral goethite. The small diameter of the fibres, measuring approximately 20 nanometers across, is what makes the tooth resistant to the introduction of structural flaws, as it gets larger.

“This discovery means that the fibrous structures found in limpet teeth could be mimicked and used in high-performance engineering applications such as Formula 1 racing cars, the hulls of boats and aircraft structures,” Barber says.
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