Quick – name the strongest biological substance in the world. Is it the enamel that coats our teeth? Is it spider silk, with it’s stronger-than-steel tensile strength? Close, but no. The award goes to the limpet, a small marine snail known for it’s ability to stubbornly cling to rocks. According to British researchers, its tiny teeth are the strongest materials known to man.
The limpet doesn’t use its teeth the way most animals do, for chewing. Instead, they protrude from a small tongue, which the limpet uses to scrape food off of rocks. What makes the limpet unique is that in doing so, it’s not unusual for the ultra-hard teeth to slough off some bits of rock as well.
To test the strength of the teeth, Asa Barber of the University of Portsmouth and his colleagues ground 10 of them into powder and fashioned them into a dog bone shaped object. Attached to a device called an atomic force microscope, force was applied to the ends of the samples (which were 1/100 the width of a human hair at their thinnest) until they broke. The result? They could withstand up to five gigapascals (GPa), or 5x more than most spider silk.
For scale, imagine a single piece of spaghetti supporting 1,500 kilograms. That’s much stronger than Kevlar, and on-par with the very best man-made carbon fiber materials.
Barber and co. found that the teeth are made of a mineral-protein composite, unlike anything else known to man.
“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,” he said.
The limpet’s teeth are particularly interesting because they appear to be flawless, and flaws are what cause failure in tensile strength tests. The thinness of the fibers that make up the teeth appear to be perfect for preventing holes, gaps and irregularities.
As for biologists who have studied limpets for years, they’re not surprised. One described limpets as “bulldozers of the seashore,” noting the way they excavate rock in their search for food.
Moving forward, the discovery may have application in the construction of high-strength materials for boats, aircraft, dental fillings and more.