A leap in innovation .. Smart skin changes color like a chameleon

Mohamed Ramadan

Scientists are finally on track to develop skin like a chameleon. A team of researchers at Emory University has created intelligent skin that can change color in response to changes in the environment, such as heat and sunlight.

Photonic crystals and aqueous gel
Details of that innovation were published in the American Chemical Society's ACS Nano journal in mid-September. The researchers developed artificial skin using photonic crystals and hydrogel in an unprecedented way inspired by the chameleon. Thus, this skin can change its color with the stability of its structure by keeping its size unchanged, which was the main obstacle to the development of smart leather color changing.

Many organisms have the ability to change their color according to changes in their surroundings. Chameleons are the most famous of all, and scientists have tried hard to understand this amazing phenomenon to simulate it, which was not easy at all. The skin color of a chameleon is not as dependent on color dyes as in most organisms, but rather on tiny particles called photonic crystals.

These crystals have a very unique characteristic, because, although transparent, they can reflect some wavelengths of light, and allow others to pass through them in such a way that they appear to have their own color.

The apparent color, as a result of the reflection of specific wavelengths of the light beam, depends on the precise distance between these photonic crystals. These crystals exist in a particular pattern repeated on the skin of the chameleon, which enables them to change their color by controlling the distances between the crystals to show the desired color.

Color change versus shrinking size
Scientists simulated what is happening in the skin of a chameleon by using similar photonic crystals and incorporating them into a water gel to develop artificial skin. By expanding or narrowing the size of the hydrogels, the distances between photonic crystals can be controlled and the color changed. Accordion musical instrument - caused the volume of artificial skin to change very dramatically, leading to instability of its structure and therefore can not be used.

"Scientists have been working on photonic crystals for a very long time to create intelligent, color-changing skin for use in many applications," said Khaled Selita, a chemistry professor at Emory University and a member of the research team. Size significantly to change color! ".

To overcome this obstacle, the research team went to a deeper study of the chameleons, to understand how they can change color based on photonic crystals, while at the same time their size remains unchanged.

So the researchers watched videos with slow-motion depiction of the chameleon skin color change, noting that photonic crystals matrices do not completely cover the chameleon skin but are distributed through a dark matrix, giving the chameleon the ability to change its color while the size remains the same.

The dark matrix
That observation inspired the team with a new idea in which synthetic skin could be ideally synthesized. The researchers combined photonic crystals with a hydrogel as usual, and then merged that hydrogel into matrices into another hydrogel without photonic crystals. This second layer of hydrogel can play the same role as a dark matrix in the skin of a chameleon.

By exposing the new artificial skin to natural sunlight for ten minutes, its color actually changed from yellow to green with its volume unchanged.The second layer of hydrogel compensated for the change in the distance between photonic crystals to keep the size of that smart skin intact.

This innovation is a first step on the road to making smart leather that can change its color according to environmental changes, which can be used in many important applications in the fields of chemical sensing, camouflage and commercial fraud.