This illustration (figure 1) was realized with Inkscape, inspired from a figure in an article published in Nature Communications by J. Teyssier and co (Volume 6, article number 6368, year 2015). The title of this article is “Photonic crystals cause active colour change in chameleons” and can be view and downloaded on the website of the Journal.

The original figure is called “figure 1” and is divided in different parts: photographies of panther chameleon (Furcifer pardalis) in different emotional states (relaxed or excited), which corresponds to a typical main coloration of their bodies, an illustration of the skin color change on the CIE color model, a cross-section of chemically tainted chameleon skin and electron imaging of the surface of the skin. I also inspired myself from their “figure 2”, which shows experimental results obtained using electrons and photons (light) as probes, in scanning electron microscopy and optical spectroscopy, respectively.

Principally, the paper illustrate the connection between the skin nano-protuberances ( guanine nanocrystals) and the final color of the chameleon. The distance between the protuberance will influence which type of light is reflected from the skin. By stretching and compressing the skin, the chameleon can modify the distance between these nano-protuberances. Light passing through a prism will display a rainbow like pattern: each light color corresponds to a specific wavelength (the distance between two maxima in the wave). So each color in the visible light has a slight different wavelength, this means that the chameleon skin, with its regular protuberances, can reflect light with a specific wavelength. If the distance between the protuberances change, the light color reflected change, and so is the overall color of the chameleon (as we percieved the light reflected off the object to be able to see it with our eye). This interaction between regularly spaced nano-objects is well known and is regulated by the usual Maxwell equations. This type of phenomenon happens in nature, from mineral (opals) to plants (berries). The objects reflecting light in this manner are called photonic crystals.

For my thesis, I wanted to use this good exemple of photonic crystal, where the distance of the nano-objects change the light reflected back. But I did not need all the illustrated part present in the article, and I wanted to simplify the final message.

I therefore draw a chameleon, using the basic drawing tool, point by point, based on the photographies (see post “Inkscape: butterfly” for more details). I then made the illustrations of the close-up view of the skin. In Inkscape, it is easy to copy-paste an already drawn object (short-cut: “Ctrl” key pressed together with “D” key). It is also possible to work in layers, meaning that objects can be set behind or in front of others. The light colored triangle, showing the resulting coloring of the chameleon, are simply made transparent, using the color menu.