Chameleon changes color with nanocrystals

Swiss scientists from the University of Geneva have established how a chameleon changes its skin color. It turned out that the animal uses the combined method of changing color. Particles of his skin have several pigment colors, and at the same time, he uses structural coloring to increase the color choices.



Until the end of the 20th century, it was believed that all animals that can change their color, use mechanisms that rearrange the skin surface painted in different colors (pigment) cells. Combining, the cells give out different colors and shades. However, a couple of decades ago, it was discovered that many creatures use the so-called structural coloring.



This mechanism is associated with the characteristics of the passage of light through thin translucent films. When light falls on a film, a part of it is reflected by its upper layer, a part gets inside and is reflected from the inside of the other side of the film. The outgoing light interferes with the previously reflected radiation. The result of the overlay depends on the thickness and refractive index of the film. But under certain conditions, the white light reflected from the film becomes colored. Some butterflies, and, as it turned out, chameleons successfully use such a mechanism.

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Butterfly wing under the microscope





Interference of light on the film



Chameleons have initially colored cells (brown, red and yellow), as well as special cells with crystals inside that reflect and refract light. In a special way, straining and relaxing the skin, they rearrange the position of the crystals so as to obtain light of the desired color at the exit. In addition, in the deepest subcutaneous layer, scientists have found cells with the largest crystals. Apparently, this layer helps animals to reflect infrared radiation, keeping its temperature under the hot tropical sun.