IN DAYS of old, knights protected themselves in armour made up of tough, interlocking "scales". This idea might one day be revisited, with future soldiers decked out in scales inspired by the almost impenetrable skin of the "dragon fish".
This fish, Polypterus senegalus, is a tough beast whose strong bite and sturdy exoskeleton has kept its species going for 96 million years. Each of the scales that cover its long body is made up of multiple layers; when the fish is bitten, each layer cracks in a different pattern so that the scale stays intact as a whole (Nature Materials, doi.org/frkx9r).
Now we know how the different types of scales work - as a series of joints between "pegs" and "sockets", allowing the fish to bend as it swims. This combination of flexibility and strength is perfect for human armour, says Swati Varshney of the Massachusetts Institute of Technology, speaking at the Society for Integrative and Comparative Biology meeting in San Francisco earlier this month. She and colleagues performed X-ray scans of scales, reconstructed the shapes and then worked out how they slotted together.
Scales near the flexible parts of the fish, such as the tail, are small and allow the fish to bend. Those on the side, protecting the internal organs, are larger and more rigid. Their joints fit together tightly so that each peg reinforces the next scale rather than allowing it to flex.
The researchers created computer models of the different scale types and blew them up to 10 times their original size. Using a 3D printer, they printed a sheet of 144 interlocking scales out of a rigid material (an early prototype is pictured). The group hopes to eventually develop a full suit of fish-scale body armour for the US military that could replace the heavy Kevlar armour currently used, but Varshney says this is still some way off. Such a suit would mimic the fish: rigid and strong across the torso and more flexible towards the joints.
These fish are promising models for human armour because they have already tested out engineering designs on themselves, says Dominique Adriaens of Ghent University in Belgium. Once the design is pinned down, researchers could use different materials to make suits. Ceramic, for instance, would provide heat protection; metal could prevent punctures.
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Body armour to scale up by mimicking flexible fish
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Body armour to scale up by mimicking flexible fish
