Limpets teeth found to be the strongest natural material
For years, spiders’ silk was thought to be the strongest natural material on Earth, but now there is a new contender: the teeth of limpets.
Limpets are molluscs that cling with surprising tenacity to rocks and stone surfaces in intertidal areas, but this is not achieved using their teeth. Adhesion to the surface is actually done by a large muscular foot. Common limpets (Patella vulgata) make an indentation in the rock, a home scar, on which they live and although they move around to feed they always return to the same indentation. They actually use their teeth to scrape algae off of rocks and into their mouths.
The underneath of a limpet’s tongue, known as a radula, has tiny teeth containing small fibres of the hard iron ore mineral goethite, which forms in the limpet as it grows. The teeth are optimised for strength since they need to be extremely strong and hard when rasping over rock surfaces during feeding to avoid abrasion.
The research was published in the Royal Society’s journal Interface on 18th February 2015. Small fragments of teeth were tested to examine the tensile strength – the amount of force they can withstand without breaking. Researchers used atomic force microscopy to pull apart the tooth material down to the level of the atom with the samples being approximately 100 times thinner than one single human hair. It was found that on average, limpet teeth have a strength of around five GPa (gigapascals) approximately five times greater than most spiders’ silk. The material tensile strength of limpet teeth is also approaching values comparable to those of the strongest man-made fibres.
Interestingly, the strength of the limpet tooth material was independent of size. In general, larger structures are weaker and break more easily than smaller structures. The discovery that limpet tooth material does not follow this rule means that the small fibres of goethite could well be imitated in the development of material for high performance engineering applications such as Formula 1 racing cars, aircraft structures and dental restorations.
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