mother-of-pearl is a unique natural Material. Molluscs such as snails and clams make it a tank against Predators though. Because of its iridescent sheen, it is often used for jewelry and art objects. But mother-of-pearl, impressed by his strength. The Material can withstand great mechanical stresses without breaking. This property is due to the characteristic structure of the material: In an organic framework that is based on Chitin, are stored in tiny, stacked plates made of calcium carbonate. The composite is built up in this way like a brick wall.
This high degree of order baffled, when it is remembered that a large number of individual cells – secretes each – at various Points in the organism Material. How the perfect structure of the Mother-of-pearl? There is a conductor in the orchestra of the cells? These issues is now being pursued by a group of scientists around Igor Zlotnikov of the TU Dresden.
The shell of a Mollusc in cross-section In an organic framework that is based on Chitin, are tiny, stacked plates made of calcium carbonate embedded. : Image: Igor Zlotnikov
the structure of The Mother-of-pearl begins in a disorderly fashion. Many of the individual cells of the so-called mantle tissue of molluscs, tiny carbonate plates and are deposited with the Chitin scaffold in layers. Since this is done on an uneven, organic surface, in the case of malfunctions. These show up as stages.
Defects to the dress
Each level rises to a helical displacement and ends at a such. These disorders have opposite topologies, so there are the right – and left-handed Defects. As the researchers Zlotnikov report in the journal “Nature Physics” runs each of the Defect by a plurality of layers of the composite material therethrough so that a kind of Helix is the result. While the mother-of-pearl layer is thicker, to approach the mirror-image Defects in pairs to each other. This will cancel one after the other. The result is a uniform structure in the mother-of-pearl.
For their study, the researchers have the high-energy, nano-meter size of the focused beams of the European synchrotron radiation source ESRF in Grenoble was used. With the method of holographic x-ray nano-tomography, they received three-dimensional images of Shell fragments of the painter’s mussel (Unio Pictorum). In the evaluation of the raw data, the researchers used Machine learning methods for pattern recognition. In this way they were able to model the growth of the Mother-of-pearl. With increasing layer thickness, the number of disturbances decreased very rapidly. The course of the decrease follows a law of exponential Decay.
Synchronized growth processes
The researchers found that the screw-shaped Defects attract over a distance of up to 50 micrometers across, in a sense. They produce internal distortion, and thus a Voltage in the Material. This phenomenon of liquid crystal systems or crystalline materials. Because of these fields of Tension forces between the defects of the act if the direction of rotation is opposite sense of the Helices, attracted to exist.