Spider silk is no longer the strongest naturally-produced substance known to humans. A team of scientists at the University of Portsmouth in England has discovered that the strongest natural substance is actually found in the teeth of the limpet, a vegetarian sea snail. Tests on their tensile strength have shown that they can withstand stresses between 3.0 to 6.5 GPa, with the mineral protein within them able to endure about 4.9 GPa. This is about five times more than that of spider silk, which is merely 1.3 GPa. Comparatively, human teeth can only withstand about 0.5 GPa. Moreover, they also outperform Kevlar (3.6 GPa), titanium, and steel alloys.
Limpets, referring to a group of predominantly freshwater gastropod mollusks, have conical shells that are approximately 5 cm in diameter. While the name refers to various snails fitting that description, “true” limpets live in the intertidal zone, clinging strongly to surfaces and moving using their “foot.” The teeth consist of goethite-based nanofibres within a chitin matrix. Goethite, an iron oxyhydroxide mineral, was used as a dark drown pigment in ancient times and is used nowadays as an iron ore. Chitin is a substance most commonly found similar crustaceans, fungi, and in the beaks of octopuses and squids. The substance is comparable to keratin in humans, with which our hair and fingernails are made. The teeth of these gastropods are used to consume algae along rocks, and therefore must be resistant to prolonged contact with the rough, jagged surfaces.
It is also very notable that the material of the small, barb-like teeth does not lose strength with increased size, as often occurs with many substances. The increased number of flaws in large-scale structures makes them more prone to failure, and often too weak for practical use. This is not the case with these typically one-millimetre long teeth, as the strength has been found to stay the same even with changing sizes. The filaments are very tiny (1/100 the diameter of human hair), creating a high mineral volume ratio, resulting the ability to withstand stress even in larger arrangements.
Already known for clearing algae and barnacles from ship’s hulls, limpets now have a new contribution to the transportation industry. Research into the structure of their teeth will result in applications in sectors such as the automotive and aerospace industries. They could possibly be used in the bodies of aircraft and vehicles (i.e. Formula One racecars), as the material is both strong and fairly light. The discovery of the properties of this material is a step forwards in the research being conducted to find naturally-derived substances that can replace steel allows in modern-day applications. The commercialization of this technology will change the safety and durability of high-performance machines.
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