Artificial skin changes color like a squid

Researchers construct a camouflage skin that adapts itself to the ground

Cuttlefish can change their color in no time © Jenny Huang / CC-by-sa 2.0 gen
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Masters of camouflage as a role model: researchers have recreated the dynamic skin of the cuttlefish. The thin, multi-layered camouflage system automatically recognizes which pattern the substrate has and adapts to it - without the need for external input. "Intelligent" envelopes based on this principle could even camouflage objects on changing surfaces in the future, as the researchers report in the journal "Proceedings of the National Academy of Sciences".

Cuttlefish use a sophisticated three-layer system to quickly adapt to the color and pattern of the seabed: the skin is filled with muscle-contractible pigment cells, the chromatophores. Under this layer of paint sits a layer of likewise controllable iridescent cells: they reflect certain portions of the light and intensify the pigment colors. The third layer forms a layer of white cells that provide the contrasting background. There are also light-sensitive cells in the skin which, in addition to the eyes of the squid, provide information on what the background looks like.

"The special thing about the cephalopod skin is the coordinated action of cells, muscles and light-sensitive organs, " explain Cunjiang Yu from the University of Houston and his colleagues. Only this allows the squid to change their color and pattern within milliseconds and camouflage themselves. A technical system that can adapt itself to the underground in a similar way, the researchers have now developed and tested for the first time.

This replica squid skin can change its color independently - depending on the surface. © Yu et al. / PNAS

Color capsules, diodes and a flexible carrier layer

The artificial squid skin has similar basic elements to those of the natural model: here too there are dynamically controllable color cells, a white background layer and light sensors. The top layer of the artificial "Tarnhaut" consists of small capsules with a heat-sensitive coloring material. It is black at room temperature, colorless at temperatures above 47 degrees Celsius, which makes it possible to control the color of this layer in a targeted manner.

Below the capsules, after a thin, white contrast layer, follows a fine network of silicon diodes, which heat the ink capsules in spots and thus trigger the color change. After a carrier layer of polymer, the final element is the final element in order to make the whole thing "intelligent": Photodiodes, which register the brightness of the background and pass on corresponding impulses to the heating diodes. "The reactions of the photodiodes define the pattern of heating and thus the resulting color pattern, " explain the researchers. display

Dynamic black and white pattern

Thanks to the miniaturized components, the artificial skin of the camouflage is only around one millimeter thick and, thanks to the flexible polymer matrix, very flexible, as the researchers report. For the tests, they put a piece of it on a light table with differently cut black masking masks. Within a second or two, the system responded to the background and reproduced the black-and-white pattern of the light table with its color cells.

The artificial skin of the camouflage also adapts to moving patterns Yu et al. / PNAS

"The whole thing works without user input or external gauges", emphasize the researchers. And even moving patterns could reproduce the artificial squid skin, as the experiment showed: the system also adapted to a bright square, which slowly moved across a black background.

According to the researchers, this artificial octopus skin makes a way to camouflage bodies that adapt to their own surface. Because of its flexible, flexible construction, such a system can also be easily dangle around objects of all kinds. This artificial octopus skin could be used, for example, for camouflage, but also to give objects deliberately changing striking colors or patterns. (Proceedings of the National Academy of Sciences, 2014; doi: 10.1073 / pnas.1410494111)

(PNAS, 19.08.2014 - NPO)