This amazing metal teeth of ants

Thanks to an unusual combination of materials that include metals, the jaws of ants are just as hard as our teeth, but much stronger

Ants have to use 60% less force to bite things than animals with normal teeth. This allows them to effortlessly cut leaves or even break the shells of other insects, although their jaws are often finer than a human hair.

His trick is a cutting edge that can be much sharper than our best composites, thanks to embedded metal atoms. The discovery corresponds to a research group at the University of Oregon that has published its findings in Nature.

In humans, tooth enamel is made up of calcium phosphate crystals embedded in a protein support structure. Instead, the edge of ants’ jaws is made up of a homogeneous material whose proteins are hardened with metal atoms such as zinc or manganese. In other words, they cut like knives.

This inclusion of metals makes the jaws of ants comparable to classic biocomposites such as teeth or claws of crabs, but with a more precise structure and also more resistant to fracture.

The jaws of ants and the stinger of scorpions contain metal

The Oregon team has been researching this type of biomaterials enriched with heavy elements for some time, a material that is not only common in ants, but also in scorpions, spiders and some marine animals.

For a long time, it was a mystery how these composites are built in animals. The teeth of marine worms have a very high metal content, up to 18%, and also consist of fine pieces of metal embedded in the protein of the jaws. But according to measurements, the metal atoms are not connected to each other.

Instead, the working group has shown, with the help of atomic probe tomography, that the metal is homogeneously distributed even in the finest structures. Due to their special chemical properties, these metal atoms function as “cross clamps” that squeeze the proteins within themselves and together, making the material harder.

Therefore, the material from which the teeth of ants or the stingers of scorpions are made has a uniform structure. In contrast, in the composite materials of other animals, hard substances are found together with soft ones, and both components absorb loads very differently. For example, the material of human teeth can break at the boundary between the hard mineral and the most flexible protein, especially in very fine structures.

In comparison, for example, the edge of the ant’s jaw, which is smooth and cross-linked by zinc, can be much finer and therefore much sharper than any die. In the leaf-cutter ant ( Atta cephalotes ) it is only 50 nanometers thick.

Chemical crosslinking of metal atoms has another effect. Metal forms chemical bonds with proteins, and these can loosen and reweave. This makes these metal-containing biomaterials extremely resistant to abrasion. If cracks appear in the material, it can heal on its own, because the metal atoms simply re-establish the bonds that had been released.

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