Spider's silk has long been the strongest natural material known to man, prompting researchers to attempt to uncover its secrets so they can replicate its remarkable properties in man-made materials. But scientists now have a new source of inspiration in the form of limpet teeth, which are made of a material researchers say is potentially stronger than spider silk, is comparable in strength to the strongest commercial carbon fibers, and could one day be copied for use in cars, boats and planes.

Limpets are aquatic snails with conical hat-shaped shells that cling to rocks on coastlines around the world. Anyone who has tried to pull a limpet from its perch knows what a difficult task that can be. However, the teeth that boast the impressive tensile strength reported by the researchers from the University of Portsmouth aren't used by the limpet to cling to the rock – this comes courtesy of a mix of suction provided by its muscular foot and adhesive mucus – but to scrape over rock surfaces to remove algae for feeding.

To examine the tensile strength, the researchers used atomic force microscopy to pull apart a sample of limpet tooth material all the way down to the atomic level. Using a sample almost 100 times thinner than the diameter of a human hair, they found the tensile strength to range from 3 to 6.5 GPa (gigapascals), which is potentially the highest ever recorded in nature. (For comparison, the tensile strength of spider dragline silk as around 1.3 GPa, while steel is typically around 1.65 GPa.) Interestingly, the strength of the limpet tooth material was found to be the same regardless 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," says Professor Asa Barber from the University’s School of Engineering, who led the study. "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."

The researchers found that limpet teeth contain goethite, a hard iron bearing hydroxide mineral that is the main component of rust and bog iron ore and which forms in the limpet as it grows.

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

The team's research appears in the Royal Society journal Interface.

Source: University of Portsmouth

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