Mighty mollusc: Limpet teeth have super strength

The teeth of the common limpet, an unremarkable mollusc found along the European sea shore, may be made of the strongest natural material known to man, scientists said Wednesday.
If it can be copied in the lab, the result would be a super strong yet light material for repairing broken teeth and making bulletproof vests or building cars and planes of the future, the researchers reported in the Royal Society journal Interface.
"Until now we thought that spider silk was the strongest biological material," said the study's lead author Asa Barber from the University of Portsmouth in England.
"But now we have discovered that limpet teeth exhibit a strength that is potentially higher."
The teeth of the limpet, each less than a millimetre (0.039 inches) long, are mounted in rows on a tongue-like feature called a radula.
The mollusc uses them to feed by grating nourishing algae off rocks.
Lab experiments used "atomic force microscopy", a method to pull materials apart down to the level of the atom, to test the teeth of Patella vulgata, an edible sea-snail species with a greyish-white shell about six centimetres (2.4 inches) long.
"Limpet teeth... are an example of a material produced biologically for strength, especially as these teeth need to be mechanically robust and avoid catastrophic failure when rasping over rock surfaces during feeding," the authors wrote.
The teeth had a tensile strength, the maximum stress a material can withstand when stretched or pulled without failing, of between three and 6.5 gigapascal (GPa).
By comparison, spider silk has a tensile strength of no more than 1.1 GPa, said the team.
Further examination revealed the tiny teeth were made of a hybrid material of both organic and inorganic elements -- including long and very thin nanofibres of goethite, an ultra-hard mineral.
"The mechanical strength of the limpet tooth is comparable to that of the strongest man-made fibres," including a 6.5-GPa carbon fibre used in building aircraft, said the study.
"Biology is a great source of inspiration when designing new structures," added Barber.
"But with so many biological structures to consider, it can take time to discover which may be useful."