Would you put such trust in your bones to hold you up and move you around if you knew they were made from jelly and chalk? Hydroxyapatite is the inorganic, mineral component - a brittle, white, calcium-based, chalky material. Collagen, the organic, carbon-based part of bone, "is very similar to gelatine", says Andre Studart, a materials scientist at the Swiss Federal Institute of Technology in Zurich. Yet from these weak raw materials, nature produces a strong, flexible, self-healing structure. Living cells guide the growth of a complex, rigid frame that houses blood vessels and supports the entire body. Trying to better understand this complex structure and how it works has kept teams of scientists busy for many years. And bone is not the only natural structure worth investigating. Nacre, also known as mother-of-pearl, is extraordinarily fracture-resistant. Dentin in the teeth is similar to bone, and is comprised mostly of calcium minerals, water and organics in an intricate structure that, beneath the enamel layer, is strong enough to worry steak or crack nutshells. Armour plates seen on fish and armadillos are models of materials that are flexible, puncture-proof and water-resistant. Research reported in February 2015 suggests that limpets' teeth, endowed with nanometre-scale fibres intertwined with minerals, may be the strongest material that nature has crafted.
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