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Color-changing robo-chameleon showcases promising camouflage tech

  • A robot modeled on a chameleon and developed by South Korean researchers can change colors to match its surroundings.
  • Like real chameleons, the robo-chameleon collects information from its environment in real time, but the way it reproduces the colors on its artificial “skin” is different.
  • The researchers say they hope the system will in future be able to read and mimic patterns as well.
  • If colors and patterns can both be replicated in real time, it could pave the way for clothing that essentially makes the wearer invisible.

It doesn’t sport swivelly eyes or an absurdly long tongue, but a new robot does boast of a chameleon’s most eye-catching trait: being able to change colors on demand.

With its clunky, segmented body, the robo-chameleon unveiled by South Korean researchers could easily be mistaken for a children’s toy or a real chameleon in body armor. It’s neither. It is, in fact, an embodiment of cutting-edge camouflage technology.

Or at least, cutting-edge for muggles, or non-magical humans. The artificial “skin” could very well be a precursor to invisibility cloaks à la Harry Potter.

Hyeonseok Kim, a co-author of the new paper published in Nature Communications, said he was struck by the chameleons he had seen at zoos, especially their ability to don different colors. He decided to model the robot on these Old World lizards.

There are currently more than 200 known species of chameleons, most of which are native to Madagascar, a biodiversity hotspot in the Indian Ocean. They come in all sizes, from the chunky Parson’s chameleon (Calumma parsonii) that can grow to 69 centimeters (27 inches), to the smallest, just shy of 1.4 cm (0.55 in). They all move with a halting grace, their forked feet clutching branches, freewheeling eyeballs surveying their nook.

A Parson’s chameleon. Image by Rhett A. Butler.

To create a model like this, the researchers had to answer two fundamental problems: what will be the input, and what will be the output? For the first, the robo-chameleon collects information about its surroundings through visual cues, similar to a real chameleon. The latter use all-seeing eyeballs to read the environment. The robot uses color sensors to capture the intensity of red, green, and blue light. These primary colors combine to form the colors visible to humans.

Then comes the more complicated matter of reproducing the legible visuals. Chameleons can display various colors by using the muscle cells of the skin.

“Chameleons can change color thanks to the migration of pigments and the tuning of nanocrystal within specialized cells generating structural colors,” said Michel C. Milinkovitch, an evolutionary geneticist who heads the Laboratory of Artificial & Natural Evolution at the University of Geneva.

This complex process of pigment distribution and structural sorcery that chameleons employ cannot be artificially reproduced with current technology. It’s difficult for humans to wrap their heads around this idea because it requires seeing the skin not as a wrapper around the body but as a living organ.

The robo-chameleon records the colors in the environment and projects them onto its “skin.” The skin is like a screen where colors and patterns are produced with thermochromic liquid crystal ink, a substance that responds to differences in temperature.

Image courtesy of Hyeonseok Kim et al.

Today, it’s possible to buy color-changing mugs online that display predetermined patterns, but nothing quite as sophisticated as something that uses new information from the environment to alter itself in real time.

Milinkovitch, who was not involved in the new research, called the technology “impressive,” noting that, in some respects, the robo-chameleon could do even more than its wild-born counterparts.

For example, real chameleons cannot disappear into just any background.

Changing colors is not even singularly about camouflage for these lizards. There is growing evidence to suggest that chameleons use it as a way to communicate too. Sometimes, they want to blend into the environment to avoid predators or be inconspicuous to potential prey.

At other times, they have been observed relying on flashy, colorful displays to distinguish themselves, especially when trying to attract mates or frighten off competition.

“We plan to study more advanced artificial camouflage systems by developing an artificial intelligence-based sensing system that can collect not only color information but also pattern information,” Kim, the paper’s first author, said in an email to Mongabay.

Such advancements would make the technology especially useful for militaries that use camouflage in their routine work. Artificial crypsis, or concealment, first emerged as part of defense research. Other applications lie in the domains of art, architecture and clothing.

“If an advanced camouflage system that can respond to various patterns is developed, it can be an application technology for invisible clothing which completely hides from the surrounding background,” Kim said.

Citations:

Kim, H., Choi, J., Kim, K. K., Won, P., Hong, S., & Ko, S. H. (2021). Biomimetic chameleon soft robot with artificial crypsis and disruptive coloration skin. Nature Communications12(1). doi:10.1038/s41467-021-24916-w

Teyssier, J., Saenko, S. V., Van der Marel, D., & Milinkovitch, M. C. (2015). Photonic crystals cause active colour change in chameleons. Nature Communications6(1). doi:10.1038/ncomms7368

(Banner Image:  Instantaneous crypsis of the chameleon robot. The robot crawls on the background and changes its skin color according to the background color. Image courtesy of Hyeonseok Kim et al.)

Malavika Vyawahare is a staff writer for Mongabay. Find her on Twitter: @MalavikaVy

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