Scientists have developed a new material inspired by cephalopod skin (octopi, squid) that automatically changes color in response to its environment, getting one step closer to true adaptive camouflage. While the prototype material only changes between black and white, lead researchers Cunjiang Yu at the University of Houston and John Rogers at the University of Illinois at Urbana–Champaign say that they have the basic principles hammered out and can now design a more complex material.
“There are analogies between layers of our system and those in the Octopus skin, but all the actual function is achieved in radically different ways,” says Rogers, Ed Yong at National Geographic reports. “The multi-layer architecture works really well, though. Evolution reached the same conclusion.”
Multi-layered adaptive material functionally similar to octopus skin
Octopus skin changes color using three different layers of cells containing different kinds of pigments: one layer can produce reds and yellows, another produces greens and blues (cell in both layers are called chromatophores), and the bottom layer diffuses light to brighten the other two (leucophores). Since the skin changes color when the cephalopod’s muscles expand or contract the chromatophores, it can adapt to its surroundings almost instantaneously.
Instead of trying to copy the cells and muscles behind nature’s camouflage, Yu and Rogers have reverse engineered something that gives a similar effect. Their top layer has a dye that is either black or transparent, depending on temperature, while the second, passive layer mimics the leucophores giving off a constant white light, and the bottom layer is a diode connected to a light sensor, heating up the dye in response to light.
The effect is that when a light is shone on the material, it automatically changes to match the light’s pattern within about a second.
Researchers plan major improvements
If the material were limited to black and white it would be pretty limited in application, but Yu and Rogers say that adding more layers and more colors is easier than it might seem. They also have plans to control the dyes with changing electric fields instead of heat so that the material can react more quickly.
This still does leave one big question, which is how a design that is basically reflective can be adapted for use as camouflage. Camouflage should either blend in with its surroundings or match whatever is behind it – if you look at a surface and see a rough reflection of yourself, you’re going to notice. It’s not really understood how squids determine what their skin should look like, but they adapt to look like the rocks around them, not the animals they’re hiding from.