Image copyright Cunjiang Yu Image caption Researchers tested out the material on the initials of their workplace - the University of Illinois 
 
 Based on the camouflage abilities of octopuses and cuttlefish, engineers in the US have built a flexible material that changes colour to match its surroundings. 
 
 The new design features a grid of 1mm cells, containing a temperature-driven dye that switches colour on demand. 
 
 So far it only responds in black-and-white, but the team hopes that the principles of their design will have commercial and military applications. 
 
 The work appears in the journal PNAS. 
 
 Senior author Prof John Rogers, from the University of Illinois, said the new sheet was the fruit of a collaboration between experts in biology, materials, computing and electrical engineering. 
 
 "Animals in the natural world - particularly cephalopods: octopus, squid and cuttlefish - have really spectacular colour-changing capabilities," he told BBC News. 
 
 Layers of potential 
 
 Prof Rogers' team set out to see what could be learned from such natural examples, and build a new material based on those insights. 
 
 Image copyright GREGORY OCHOCKI/SPL Image caption Octopuses, known for their camouflage abilities, also use a special three-layered skin 
 
 In particular, they copied the three-layer design seen in the skin of these animals: the top layer contains the colours, the middle layer drives the colour changes, and the lower layer senses the background patterns to be copied. 
 
 Each component in the new sheets, however, does its job quite differently from the three layers that do the same job in an octopus's skin. 
 
 The bottom layer in the engineered system contains a grid of photosensors, which detect changes in light and transmit that pattern to "actuators" in the layer above. 
 
 These actuators take the place of muscles within octopus skin, which control colour-changing organs in the surface layer. 
 
 Media playback is unsupported on your device Media caption When the background changes, the cells within the material switch colour within one or two seconds 
 
 The uppermost layer in the artificial version uses a temperature-sensitive pigment, which goes from black to transparent at precisely 47C. That temperature change has to be produced by a current from the actuators underneath. 
 
 This is both a much less efficient system, and a much more limited colour repertoire, than what shimmers across the eight-legged canvasses of the sea. 
 
 Nonetheless, Prof Rogers' team is justifiably proud of its achievement. 
 
 "This is the first full, working system of its kind - it looks like a thin sheet of paper," he told BBC News. 
 
 "But it's nothing close to being ready to deploy, in a military setting or anything else. It's really a beginning point, to focus on the engineering science around how you might create systems that have this type of function." 
 
 Image copyright Cunjiang Yu Image caption The flexible material contains square 1mm-by-1mm, colour-changing "cells" 
 
 A number of folks have approached us for completely other classes of application, that I wouldn't initially have guessed at Prof John Rogers, University of Illinois 
 
 In particular, the system needs to improve its spatial and colour resolution, and its efficiency - possibly by incorporating solar cells instead of using external power. 
 
 This could all be done by adapting existing technology, Prof Rogers said, such as that seen in flat-screen displays. 
 
 Prof Anne Neville, a UK expert in biologically inspired technologies, said the work was of a "very high standard" and was impressed by the number of different disciplines involved. 
 
 "It's very innovative and very interesting," said Prof Neville, who is the Royal Academy of Engineering Chair in Emerging Technologies at the University of Leeds. 
 
 Cuttlefish fashion 
 
 The applications go beyond the obvious associations of camouflage, where Prof Rogers said there is "obvious potential" - potential which led to the work being funded by the US Navy. 
 
 "What I've been intrigued by is a number of folks who have approached us for completely other classes of application, that I wouldn't initially have guessed at." 
 
 Image copyright PETER SCOONES/SPL Image caption Cuttlefish have been known to mesmerise their prey with rippling bands of colour 
 
 One of these was an art professor in Chicago, who is interested in colour-changing fabrics for high-end fashion, which could respond to ambient lighting. "In that case you probably don't want camouflage necessarily," Prof Rogers said. "Maybe you want your clothing configured so that you stand out from the crowd." 
 
 Such "anti-camouflage" would draw more inspiration from the deep sea creatures that use their skin to attract, rather than avoid, attention - like cuttlefish that mesmerise their prey with rippling stripes. 
 
 Prof Rogers has also had conversations with his own university's school of architecture, about the possibility of dynamic, colour-changing walls and other interior surfaces. 
 
 These grand designs remain some way off, however, and Prof Rogers emphasised that they are not his priority. 
 
 "Our goal as researchers is not to develop a colour-changing wallpaper. That's a vision that somebody had, for an application - and indeed, it's kind of cool. But our emphasis is more on the basics, around biologically inspired engineering." 
 
 Follow Jonathan on Twitter ||||| The most amazing skins in the world can be found in the sea, stretched over the bodies of octopuses, squid and cuttlefish. These animals, collectively known as cephalopods, can change the colour, shape and texture of their skin at a whim—just watch the ‘rock’ in the video above suddenly reveal its true nature. Their camouflage is also adaptive. Unlike, say, a stick insect or stonefish, which are limited to one disguise, an octopus’s shifting skin allows it to mimic a multitude of backgrounds. It sees, it becomes. 
 
 No man-made technology comes close. But one, at least, is nudging in the right direction. 
 
 A team of scientists led by Cunjiang Yu at the University of Houston and John Rogers at the University of Illinois at Urbana–Champaign have developed a flexible pixellated sheet that can detect light falling upon it and change its pattern to match. So far, its large pixels can change from black to white and back again. It’s a far cry from an octopus’s skin, but it does share some of the same qualities. For example, it changes colour automatically and relatively quickly—not cephalopod-quick, but within a second or so. 
 
 “This is by no means a deployable camouflage system but it’s a pretty good starting point,” says Rogers. Eventually, his team are working towards adaptive sheets that can wrap around solid objects and alter their appearance. These could be used to make military vehicles that automatically camouflage themselves, or clothes that change colour depending on lighting conditions. 
 
 Cephalopod skins have three layers. The top one consists of cells called chromatophores, which are sacs of coloured pigment, controlled by a ring of muscles. If the sac expands, it produces a pixel of colour; if it contracts, the pixel hides. These cells are responsible for hues like red, orange, yellow and black. The middle layer contains iridophores, cells that reflect the colours of the animal’s environment—they’re responsible for cooler colours like blues and greens. The bottom layer consists of leucophores, passive cells that diffuse white light in all directions, and act as a backdrop for the other colours. 
 
 The skin also contains light-sensitive molecules called opsins, much like those found in your retina. It’s still unclear what these do, but a reasonable guess is that they help cephalopods to “see” with their skin, and adapt their patterns very quickly without needing instructions from their brains. 
 
 The team drew inspiration from these skins when designing their own material. It consists of a 16 by 16 grid of squares, each of which consists of several layers. 
 
 The top one contains a heat-sensitive dye that reversibly changes colour from black at room temperature to colourless at 47 degrees Celsius, and back again. This is the equivalent of an octopus’s chromatophores. 
 
 The next layer is a thin piece of silver, which creates a bright white background, like the leucophores. 
 
 Below that, there’s a diode that heats the overlying dye and controls its colour. This is the equivalent of the muscles that control the chromatophores. 
 
 Finally, there’s a layer with a light-detector in one corner, a bit like a cephalopod’s skin opsins. All the top-most layers—the dye and the silver—have little notches missing from their corners so that the light-detector always gets a unimpeded view of its surroundings. 
 
 And the whole thing sits on a flexible base so it can bend and flex without breaking. 
 
 So, the light-detectors sense any incoming light, and tell the diodes in the illuminated panels to heat up. This turns the overlying dye from black to transparent. These pixels now reflects light from their silver layer, making them look white. You can see this happening in the videos below. Here, different patches of light are shining onto the material from below, and it’s responding very quickly. 
 
 “There are analogies between layers of our system and those in the cephalopod skin, but all the actual function is achieved in radically different ways,” says Rogers. “The multi-layer architecture works really well, though. Evolution reached the same conclusion.” 
 
 “The most exciting thing about this is that it’s all automatic, without any external user input,” he adds. 
 
 There are obvious military applications for the device and the work was funded by the Office of Naval Research. But Rogers notes that the sheets are designed to sense and adapt—they don’t necessarily have to blend in. “There are a lot of applications in fashion and interior design,” he says. “You could apply these flexible sheets to any surface and create something that’s visually responsive to ambient lighting conditions. But our goal is not to make adaptable wallpaper; it’s on the fundamentals.” 
 
 Obviously, the material will have to be improved. Since it relies on heat to change colour, it’s relatively slow, consumes a lot of power, and only works in a narrow range of temperatures. But the team used a heat-sensitive dye because it was easy; it gave them time to focus on the rest of the system. 
 
 Now that this framework is in place, they think they could improve it very easily. Rather than heating diodes, they could use components that use changing electric fields. They could replace the dyes with other substances that offer a full range of colours, beyond just black and white. And they should be able to scale the sheet up easily—Rogers, after all, has a lot of experience in building flexible electronics using commonly used substances like silicon, rather than fancy (and expensive) new materials. 
 
 But he doubts he’ll ever make something that truly matches a cephalopod’s skin. “As an engineer looking at movies of squid, octopuses, and cuttlefish, you just realise that you’re not going to get close to that level of sophistication,” he says. “We tried to abstract the same principles and do the best we can with what we’ve got.” 
 
 Does their artificial skin have any advantages over what an octopus or squid can do? 
 
 “Well, it works on dry land!” says Rogers. 
 
 Reference: Yu, Li, Zhang, Huang, Malyrchuk, Wang, Shi, Gao, Su, Zhang, Xu, Hanlon, Huang & Rogers. 2014. Adaptive optoelectronic camouflage systems with designs inspired by cephalopod skins. PNAS http://dx.doi.org/10.1073/pnas.1410494111
– Scientists have taken the first rudimentary step toward developing a material that can do what octopuses and squid have mastered: change color on a whim. Researchers at the University of Houston and the University of Illinois at Urbana-Champaign "developed a flexible pixellated sheet that can detect light falling upon it and change its pattern to match," writes Ed Yong at National Geographic. Their sheet can turn from black to white and then back to black, which the researchers admit is a far cry from the cephalopods' mad skills. "But it's a pretty good starting point," says one of the lead scientists. The technique borrows the general principle of the animals' skin, which has three layers, explains the BBC: "The top layer contains the colors, the middle layer drives the color changes, and the lower layer senses the background patterns to be copied." Scientists used photosensors to detect changes of light, and dyes responded accordingly. The research is funded by the US Navy, but plenty of non-military applications are possible, including one suggested by an art professor in Chicago who studies fashion. Think the opposite of camouflage, with material that responds to your surroundings: "Maybe you want your clothing configured so that you stand out from the crowd," says the researcher. (Click to read about a deep-sea octopus then guards her eggs for four years.)