The limpet has a tongue or 'radula' covered in tiny teeth that scrape away at the rock surfaceContinue reading the main story
Limpet teeth set new strength record
Engineers in the UK have found that limpets' teeth consist of the strongest biological material ever tested.
Limpets use a tongue bristling with tiny teeth to scrape food from rocks and also to carve out scars, which they nestle in when the tide goes out.
The teeth are made of a mineral-protein composite, which the researchers tested in tiny fragments in the laboratory.
They found it was stronger than spider silk, as well as all but the very strongest of man-made materials.
The findings, published in the Royal Society's journal Interface, suggest that the secret to the material's strength is the thinness of its tightly-packed mineral fibres - a discovery that could help improve the man-made composites used to build aircraft, cars and boats, as well as dental fillings.
The lives of limpets, from BBC Two's Rock Pool Survivors
"Biology is a great source of inspiration as an engineer," said the study's lead author Dr Asa Barber, from the University of Portsmouth.
"These teeth are made up of very small fibres, put together in a particular way - and we should be thinking about making our own structures following the same design principles."
'Better than Kevlar'
Those fibres, consisting of an iron-based mineral called goethite, are laced through a protein base in much the same way as carbon fibres can be used to strengthen plastic.
The teeth themselves are less than a millimetre long, but Dr Barber and his colleagues ground ten of them into a miniscule dog-bone shape in order to precisely measure the composite's tensile strength: the amount of force it can withstand before breaking.
The tooth fragments were milled into a microscopic dog-bone shape and glued to a lever for testing
The middle part of these samples was more than 100 times thinner than a human hair.
With either end glued to specialised levers inside a device called an atomic force microscope, the engineers applied a pulling force to each of these milled tooth samples, until they snapped.
The strength they calculated for the tooth material was, on average, about five gigapascals - some five times greater than most spider silk.
This sets a new record for biology, Dr Barber said, even when his team considered the most unusual spiders.
"People are always trying to find the next strongest thing, but spider silk has been the winner for quite a few years now," he told the BBC. "So we were quite happy that the limpet teeth exceeded that.
"One of my colleagues on the paper, from Italy, found some exotic spider silk that was about 4.5 GPa, and we measured about 5 GPa."
This measurement is about the same as the pressure needed to turn carbon into diamond beneath the earth's crust. Alternatively, as Dr Barber explained, it can be compared to a single string of spaghetti holding up 3,000 half-kilogram bags of sugar.
In terms of man-made materials, the limpet tooth is stronger than Kevlar fibres and almost as good as the best high-performance carbon fibre materials.
Limpets are a familiar sight in coastal rock pools
The key, Dr Barber said, is that its strength-giving mineral fibres are very thin - the ideal width, in fact, for avoiding holes or flaws that would weaken the structure.
This is something that engineers could learn from.
"Generally as you make something bigger, the thing that you've got has more flaws in it. And those flaws reduce the strength of the structure.
"With carbon fibre processing, they work very hard to take the flaws out of the fibres. But you could say, well, if I just make my fibres below a certain width, then maybe they wouldn't have to work so hard to get rid of the flaws."
Follow Jonathan on Twitter
No comments:
Post a Comment