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December 8, 2008, 6:11 pm

Biomimicry - copying nature's toughest materials

Mother of pearl lines the inside of many shells and is known for its beautiful colouring and amazing toughness. Now scientists have copied this biological material to produce the toughest and lightest ceramic known!

[Science Daily]

What is mother of pearl?

It is also known as 'nancre' and is found inside mollusc shells. Its hexagonal platelets are made of aragonite (CaCO3) crystals 10-20 µm wide and 0.5 µm thick separated by an organic matrix.

The beautiful irridescence occurs because the thickness of the aragonite platelets is very similar to the wavelength of visible light. This results in constructive and destructive interference of different wavelengths of light, so that different colors of light are reflected when it is viewed from different angles.

Trying to make a synthetic material as tough as nancre was a challenge. Scientists discovered a technique to copy the scaffolding of nancre by freezing seawater - by freeze casting ceramics, tough new materials could be formed.

Later, new materials were designed using the controlled freezing of suspensions in water of alumina (aliminium oxide) and the addition of the polymer polymethylmethacrylate (PMMA) - this made the alumina as tough as many aluminium alloys.

The technique opens up possibilities for creating many new light-weight, tough materials for use in energy and transportation.