MSE research shadowing programme: Mantis shrimp

Day 3 (Part 1)

Today's update will be done in 2 parts, first on some reading on what I will be learning later.

The second part of today will be a visit to research techno plaza, where I will be introduced more about biomimicry.

The mantis shrimp:

Neither a mantis nor a shrimp. They are in fact, relatives of crabs and lobsters. Pugilistic in nature, they uses their "fist" to smash open their prey's shell for their dinner. Preys including crabs, snails, and shrimps, all which scientist have thought to have the hardest shells and research have been done to minic the shells for the applications such as military armor (e.g. iron snail). However, the Mantis Shrimp have been smashing them apart, over and over again, with no visible damage to its club.

Figure 1 The mantis shrimp's club
image from: http://blogs.scientificamerican.com/observations/2012/06/07/this-psychedelic-shrimp-will-get-you-hammered-video/ , assessed 5 Dec 2012

What this means: The clubs of mantis shrimps are stronger than the shells that scientist have been researching in. Hence, NTU, in collaboration with other universities around the world, have set their goals in the research of the Mantis Shrimp.

The Club

The outer layer of the club (blue in diagram below) is made of crystalline calcium-phosphate ceramic material, hydroxyapatite crystals - the same stuff found in human bones and teeth, albeit a much denser form and with different arrangements. They are arranged in columns perpendicularly to the surface, such that it provides a system which can withstand up to 4gigapascal of pressure before it collaspe (compared to modern ceramics such as Silicon carbide - used in militaries as body armors today - which can only withstand 2 or 3 gigapascal). Only about 60micrometer thick, they have been discovered to be extremely hard, but brittle.

Figure 2 Diagram of Mantis Shrimp's club
image from: http://blogs.discovermagazine.com/notrocketscience/2012/06/07/how-mantis-shrimps-deliver-armour-shattering-punches-without-breaking-their-fists/ , assessed 5 Dec 2012

What keeps it from shattering is the layer behind it (red and yellow in the diagrm above), a fibre called chitin (commonly found in the seafish's exoskeleton) stacked in layers such that it is elastic to absorb the impact (something like a crumple zone?). This stacking is also done in a helical shape, such that the the cracks will be spread throughout the fibre, but never tearing them apart. The helical shape will not only spread out the cracks, but also minimise the spread of it.

This by itself is a very interesting theme in nature's armor. They do allow cracks to form, but the cracks are controlled so that the damage will not be too great. In humans, however, we have evolved to prevent cracks from happening as much as possible, but if one do happen (hair-line fracture, etc.), the results will be devastating.

Figure 3 The structure of the fibre in the club of mantis shrimp
image from: http://blogs.discovermagazine.com/notrocketscience/2012/06/07/how-mantis-shrimps-deliver-armour-shattering-punches-without-breaking-their-fists/ , assessed 5 Dec 2012

The green areas in figure 2 is made of the same fibres, which compresses the entire structure for the same purpose of slowing spread of cracks.

Significance (to what I've learnt so far)

The club of the Mantis Shrimp is similar to the armor systems which I have learnt about from the previous day (post: Introduction of Ceramics).

It consist of an entire system (not a single material to block any impact)
It has an extremely hard outer layer
It has an elastic inner layer to absorb impact
With exactly the same materials, the way that those materials are stacked can make a difference to its penetration resistance (talking about molecular structure here)

Additional (interesting) Facts

The striking clubs accelerate nearly similarly to a .22 calibre bullet (meaning that it can indeed withstand impacts of that velocity)
The mantis shrimp have been known to break its aquarium's glass
It strikes with a instantaneous forces of 1,500 newtons (about a car dropping on you?)
It stricks so fast that it traps bubbles
These bubbles will reach a temperature of AT LEAST 5000K (nearing the temperature of the sun!)and extremely high temperature, stunning, if not killing, its prey even if the club misses.
This effect is called shrimpoluminescence (or sonoluminescence)

University of California - Riverside (2012, June 7). Armored caterpillar could inspire new body armor. ScienceDaily. Retrieved December 5, 2012, from http://www.sciencedaily.com /releases/2012/06/120607142355.htm

MSE research shadowing programme

Wednesday, 5 December 2012

Mantis shrimp

Day 3 (Part 1)

The mantis shrimp:

The Club

Significance (to what I've learnt so far)

Additional (interesting) Facts

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