Arapaima scales inspire new body armour design!

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A team from the US are using an unlikely source of inspiration in a new design of body armour - the scales of the giant Amazonian fish species Arapaima gigas.

Professor Marc Meyers from the Jacobs School of Engineering at UC San Diego first pondered on the natural strength and resilience of the huge fishes' scales during a trip to the Amazon.

Their ability to survive in dwindling, land-locked lakes during the dry season in the company of piranha, when most other fish became a tasty snack intrigued him.

The team took Arapaima scales and embedded them into a soft rubber surface similar in density to the fish's muscle, and then simulated piranha attack using teeth from the fearsome fish, attached to an industrial strength hole punch.

While the tooth was able to penetrate the outer layer of scale, it cracked before it could reach the muscle below.

Closer inspection showed how this effective armour works. The overlapping scales act like a layer of shingles, with each scale covered in a hard, mineralised outer layer similar to human tooth enamel. This surface is also corrugated which allows it to bend without cracking. Beneath this are softer collagen fibres stacked in alternating layers much like plywood.

With this combination of hard exterior and softer internal structure the scales are able to bend, deform and flex without losing strength, allowing the fish to remain protected without losing mobility.

The insights gained from closer scrutiny of these fishes' natural defences are now being used to provide "bioinspiration" for engineers looking to develop flexible ceramics for use in a number of projects including body armour, insulation and aerospace design.

The team are now looking for further 'biomimetic' inspiration from another giant fish, the Alligator gar (Atractosteus spatula) whose scales were once used as arrow tips by native Americans, as well as from the shells of Abalone and the skins of giant Leatherback turtles.

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