18 February 2015
Title:Extreme strength observed in limpet teeth
Authors: Asa H. Barber , Dun Lu , Nicola M. Pugno
Limpet teeth could overtake spider silk as the strongest biological material known to man reports a study published in the Royal Society journal Interface today.
The teeth are a composite material made from a protein-based polymer coupled with a stronger and stiffer mineral phase. The team behind the study say the super-strength of the limpet teeth could inspire the design of new composite materials for cars, boats and planes, and even the next generation of dental restorations.
Limpets, aquatic snails with conical shaped shells, cling strongly to surfaces with their muscular suction foot. With a tongue-like appendage containing rows of teeth they rasp algae from surfaces, raking it towards their mouths for nutrients. The teeth have to be very strong to resist breaking or degrading when raking algae from hard surfaces.
Made from a protein matrix reinforced by a strong network of mineral nanofibers, the team think the teeth have an ideal mix of the two components to give them maximum strength. There is a high volume of the mineral goethite, an iron oxyhydroxide, in the teeth compared to the volume of protein polymer. What’s more, the goethite nanofibres are incredibly small in diameter, and so are smaller than the critical size above which the fibres could be prone to defects which could make them weaker.
To test the strength of the teeth the team collected limpets from Southampton in the UK and examined their teeth, which are less than a millimetre long. From the teeth, which are curved, the team had to cut out a smaller piece so they could test the tensile strength of tooth material without their measurements being affected by their shape. On this tiny scale the team used atomic force microscopy which measures the strength of materials as they are pulled apart at an atomic scale.
The limpet teeth’s strength, which was found to be independent of their size, approached the strength of the strongest of man-made fibres and could be a bio-inspiration future engineering materials.