30 Animals That Made Us Smarter by Patrick Aryee & Michael Bright

Author:Patrick Aryee & Michael Bright [Aryee, Patrick & Bright, Michael]
Language: eng
Format: epub
ISBN: 9781473533035
Publisher: Ebury Publishing
Published: 2021-09-02T00:00:00+00:00

A team of researchers led by David Kisailus at the University of California, Irvine, and by Pablo Zavattieri at Purdue University, Indiana, has been working together to study the club-like appendage of the mantis shrimp. They’ve found that the bone-like mineral and organic natural fibres inside the dactyl club combine to form what’s called a composite: a mixture of two materials with different physical and chemical properties. When combined, they create a material that has super properties. In the case of the mantis shrimp, it’s one that’s tough, stiff and light.

The club of the mantis shrimp is made up of several different parts. The outermost section consists of tiny particles of calcium phosphate – the same mineral found in human bone – and is itself surrounded by a layer of organic material. This layer provides some initial protection from the fast impacts of the club. Underneath this particle layer, organic fibres made of chitin – the same material found in the shells of insects and crabs – are arranged in a herringbone pattern. This helps to stiffen the club and really helps when it comes to smashing in prey.

Finally, the club is slammed thousands of times against the hard-shelled prey, and so it must absorb all this energy. How does it do that? David Kisailus’s team found the secret is inside the club. Here, chitin fibres are arranged in what’s called ‘helicoidal architecture’ or a flat spiral. This looks a bit like a squashed spiral staircase, where the steps circle round and round as they get higher and higher. Imagine each step is made from a layer of fibres that are lined up next to one another, like a row of pencils. Each layer of fibres is slightly rotated with respect to its neighbours.

The team discovered that when intense pressure, like a punch, is applied to this architecture, a crack starts to form. But as the crack grows it twists, and its progress is gradually slowed down by the material. This prevents what’s called ‘catastrophic failure’; in other words, really serious damage. In some ways, this spiral of fibre layers acts as a shock absorber. As cracks start to form, they follow the twisting pattern of the fibre staircase, rather than spreading straight out across the structure, which would cause it to fail. This differs from a material like glass, which, when dropped, has cracks rip straight through it, which then leads to catastrophic failure.

The team has since created and tested a range of materials, including carbon fibre-reinforced composites, all of which are based on the mantis shrimp’s club. With the added help of cameras and digital technology they’ve been able to examine how their new materials react and change. They put them up against two control samples, one of which is currently used in the aerospace industry. They wanted to see which would win in a challenge of strength and resilience.

Their experiments compared the impact resistance and energy absorption of each material when they were struck, and examined their strength after impact.

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