Composite limpet teeth strongest material in nature

The Royal Society Publishing paper, titled "Extreme strength observed in limpet teeth," reports that the teeth of limpets use composite nanostructures that consist of high volume fractions of nanofibers combined with a protein phase matrix to produce an uncommonly strong material.

Authored by Asa H. Barber (University of Portsmouth, Portsmouth, UK), Dun Lu (Università di Trento, Trento, Italy) and Nicola Pugno (Università di Trento), and published Feb. 18, the paper says:
"The teeth of limpets exploit distinctive composite nanostructures consisting of high volume fractions of reinforcing goethite nanofibres within a softer protein phase to provide mechanical integrity when rasping over rock surfaces during feeding. The tensile strength of discrete volumes of limpet tooth material measured using in-situ atomic force microscopy was found to range from 3.0 to 6.5 GPa and was independent of sample size. These observations highlight an absolute material tensile strength that is the highest recorded for a biological material, outperforming the f spider silk currently considered to be the strongest natural material, and approaching values comparable to those of the strongest man-made fibres. This considerable tensile strength of limpet teeth is attributed to a high mineral volume fraction of reinforcing goethite nanofibres with diameters below a defect-controlled critical size, suggesting that natural design in limpet teeth is optimized towards theoretical strength limits."
Limpet teeth are extremely small, measuring about 75 µm long, and thus were a challenge for researchers to extract, prepare and test to assess strength characteristics. According to the research, the strength of the limpet tooth is attributed primarily to geothite, an iron-bearing hydroxide mineral, which helps give the composite tooth strength properties on par with Toray (Tokyo, Japan) T1000 carbon fiber. 
More Info: CompositesWorld
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