The chameleon is one of the more fascinating lizards that nature has to offer – at least in terms of its colorful appearance. With over 200 different species within the family of Chamaeleonidae, over half of these are found on the island of Madagascar, off the southeast coast of Africa. Other species are also home to parts of Europe and Asia.
The chameleon comes in all different shapes and sizes, ranging from a mere 15mm to species that can get as large as 68cm. Many of these species are adorned with facial protrusions such as horns or crests, which are often times more pronounced on the male as opposed to its female counterpart. Chameleons also have an extremely good eyesight and are able to look into two directions at the same time, with the help of their pivoting eyes, allowing them a full 360° arc of vision. Within the different species of the chameleon, many are also able to change the color of their skin within mere seconds, ranging from hues of blues and greens to more prominent colors such as red and yellow.
The chameleon doesn’t necessarily only use its color changing abilities to disguise itself and camouflage against its surroundings, but other uses of the color change is that of temperature sensitivity or communication, allowing it to interact with other chameleons. The change of color in the chameleon’s skin is also a form of expressing dominance, excitement, relaxation or aggressiveness, and can also be an indication whether or not a chameleon is ready for mating.
Chameleons, colors and crystals
For a long time it was believed that chameleons are only able to change their skin color due to various pigmentations within the cell layers of their skin, allowing them to produce warm and dark colours. Whilst this is true, it doesn’t offer a great explanation as to how the chameleon is able to create different hues of colors and express brighter colors on its skin as well.
Recent research has proven that this is due to the arrangement of crystals within their highly specialized skin cells, called iridophores. The outermost skin layer of the chameleon is transparent and is made up of chromatophores, underneath which the iridophores are assembled. The specifically arranged nano-crystals within the iridophores are made from guanine, a part of the nucleic building block that make up the chameleon’s DNA. These crystals are able to reflect different wavelengths of light according to their arrangement within the cell.
The arrangement of the crystals is dependent on the mood of the animal, becoming a “selective mirror” of emotions for the chameleon. For instance, when a chameleon is in a relaxed state, the crystals within its skin will be closer to one another and will reflect shorter wavelengths of light, and will thus reflect and display colours like blues or greens. However, if the chameleon is in an excited or agitated state, the crystals in its skin will rearrange and expand, causing longer wavelengths of light to be reflected, and allowing the chameleon to express brighter colors such as red or yellow.
When the crystals in the chameleons skin are closer together, resulting in blues and greens. When the crystals are further apart however, which allows the chameleon to reflect longer wavelengths of light, resulting in reds and yellows.
How the Chameleon keeps it’s cool – Thermoregulation
In addition to its ability to change its color, the chameleon also uses the make-up of its skin cells to keep its body temperature down in a smart and efficient way. Below the top layer of reflective iridophores is another layer or cells. These are, differently to the top layers, substantially larger and also less organized in their arrangement. This scattered arrangement of the lower iridophores allows the chameleon to reflect infrared wavelengths, enabling it to redirect the heat away from its body, and ultimately allowing the chameleon to keep its body temperature cool. The chameleon has therefore been able to split its layers of iridophores into two, allowing it to become specialized in both temperature sensitivity and color change.
An example of a desert chameleon that uses this color changing ability to keep both cool and warm, is the Namaqua Chameleon. During the cooler morning hours it attracts the warm infrared wavelengths of the sun by coloring itself brown. When the heat rises the chameleon changes the arrangement of the photonic crystals in its skin so that it becomes white and no longer attracts the warm sun-rays. In addition to its color changing, the chameleon also avoids the loss of water by secretion of salts through its nasal glands and by digging holes in the sand to thermo regulate its body.
The Butterfly and Photonic Crystals
Similarly to the chameleon and other lizard species, the butterfly also has tiny photonic crystals embedded within its wings that allow it to reflect and scatter light in order to create spectacular patterns on its wings. Similarly to the chameleon, the tiny crystal particles are organised in very specific ways with some irregularities, allowing the butterfly to reflect more vibrant colors.
These newly discovered irregularities within the cells, or also called defects, allow for different wavelengths of light to be reflected and helps the butterfly to scatter or to concentrate different wavelengths to its advantage.
Ridge structure of the scales in the wings of the butterfly – allow it to reflect different light wavelengths and produce different colours.
The Blue Morpho Butterfly
An example of a butterfly that makes use of these crystals is the Blue Morpho Butterfly, which, being one of the largest butterfly species is home to the rainforests of Latin America. The butterfly’s wings are of a vibrant blue color with a black border, of which the underside is a plain brown with various eye patterns – both of these color schemes help it to attract mates but also to camouflage it from various predators. The color of the Morpho butterfly is due to the micro-architecture of the scales made up of photonic crystals in the wings of the butterfly. Each of these scales of the wing is covered in ridges, which are separated from each other at the same distance that blue wavelengths in light are – once the photonic crystals in the ridges have reflected blue light, the color is even more so enhanced by the exact position of the ridges.
These are found in various examples in nature, but can also be created synthetically. Photonic particles act as transistors and revolutionized computer systems, as these allowed for stronger and better optical computing. A photonic crystal is a particle that can transmit light and are able to specialize on different wavelengths of light – therefore either transmitting only red or blue light.
Examples of Photonic Particles:
The morphotex fabric, consisting of both nylon and polyester, uses the characteristics of the ridges and cuticles found in the morpho butterfly, in order to create a shimmering effect.
Other animals that use photonic particles to create mesmerising color patterns are lizards, beetles, butterflies, bird, fish, and many more.
Working with the Moroccan Sun
The sun is at a much higher point in the summer as during the winter, influencing the architecture in Morocco. Due to the extreme differences of the sun’s angle during the year, which in the summer is at a high point of 82°, at 58° during both autumn and spring, and at 34° during winter, a smart building material needs to be able to address the issues of:
(and also low wind velocities)
The idea of heat dissipation, reflectivity, tiles and colours
How to fuse the ideas of color changing tiles that allow for passive cooling?
Digi Fab Lab: Digital Ceramic Slip-Casting for Curvilinear Facades
Form and color: by using reflective colors, such as silver and gold, the sun’s rays will be repelled away from the building, but will funnel the wind, allowing passive cooling to happen. The idea of a passively cooling tile that combines both colors and Islamic geometry.
Digi Fab Lab: Ceramiskin: Penrose Screen wall
Reflective 3Dimensional tiles with light projection
A possible solution that combines both the reflective properties of the chameleon and butterfly‘s photonic particles and the ability of thermoregulation and passive cooling, could be a 3Dimensional tile with a wider and a narrower opening with both gold and silver paint on the inside. Depending on the position of the sun, the silver or gold paint particles will reflect the sun‘s heat rays and will cast a reflective light into the interior of the building through the tile‘s funnel. In addition to this, due to the make-up of the tile, wind will be funnelled through the opening, allowing small gaps in the wall where air comes through in an intensified manner.
The 3D tile is cited in silver and gold paint which is to resonate the sun’s heatwaves from the building, while acting as a passive air cooling funnel.
Fabrication of Tiles – 3D printing and clay moulding
Possibly fabrication methods that could produce 3D tiles
Direct digital milling of plaster and press moulding of clay or silicon moulding (Digi Fab Lab)
3D Printing of clay by FAB CLAY with the help of a transformed CNC Mill