Strength Of Materials - Blog Posts

Biomimicry

Brittle starfish shows how to make tough ceramics

Nature inspires innovation. An international team lead by researchers at Technion – Israel Institute of Technology, together with ESRF -the European Synchrotron, Grenoble, France- scientists, have discovered how a brittle star can create material like tempered glass underwater. The findings are published in Science and may open new bio-inspired routes for toughening brittle ceramics in various applications that span from optical lenses to automotive turbochargers and even biomaterial implants.

A beautiful, brainless brittle star that lives in coral reefs has the clue to super tough glass. Hundreds of focal lenses are located on the arms of this creature, which is an echinoderm called Ophiocoma wendtii. These lenses, made of chalk, are powerful and accurate, and the deciphering of their crystalline and nanoscale structure has occupied Boaz Pokroy and his team, from the Technion-Israel Institute of Technology, for the past three years. Thanks to research done on three ESRF beamlines, ID22, ID13 and ID16B, among other laboratories, they have figured out the unique protective mechanism of highly resistant lenses.

As an example, take tempered glass. It is produced by exerting compressive pressure on the glass which compresses it and leaves it more compact than in its natural state. Glass tempering is performed by rapidly heating and then rapidly cooling the material. In this process, the outside of the material cools more quickly than the inside and thereby compresses the inside. Ophiocoma wendtiilenses are created in the open sea, at room temperature, unlike tempered glass. “We have discovered a strategy for making brittle material much more durable under natural conditions. It is ‘crystal engineering’ and tempering without heating and quenching – a process that could be very useful in materials engineering,” explains Pokroy.

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