Military camouflage has been the subject of continuous improvement and research for over 100 years – ever since the realisation that, supplying troops and equipment with colours matching the ambient environment could lead to improved protection and survivability.
Camouflage comproses the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see (crypsis), or by disguising them as something else (mimesis). Examples include the leopard’s spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid’s wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. Some camouflage systems (eg. SAAB’s Barracuda) rely on this mechanism, disturbing the shape of the protected object so that even if it is detected, it can’t be easily recognised or identified.
Camouflage has been used to protect military equipment such as vehicles, guns, ships, aircraft and buildings as well as individual soldiers and their positions. Vehicle camouflage methods begin with paint, which offers at best only limited effectiveness. Other methods for stationary land vehicles include covering with improvised materials such as blankets and vegetation, and erecting nets, screens and soft covers which may suitably reflect, scatter or absorb near infrared and radar waves.
Many camouflaged textile patterns have been developed to suit the need to match combat clothing to different kinds of terrain (such as woodland, snow, and desert). The design of a pattern effective in all terrains has proved elusive. Engineers and professors over at MIT are crafting dynamic, flexible materials that mimic the responsive behavior of cephalopod skin (that’s octopuses, cuttlefish, and squid to you), animals which are able to change color and pattern to blend into their surroundings. Although the durable technology could also be used for various electronics, it’s intended for the military, after attempts to design a single pattern that worked in all terrains failed spectacularly, to the tune of billions
Some military textiles and vehicle camouflage paints also reflect infrared to help provide concealment from night vision devices. After the Second World War, radar made camouflage generally less effective, though coastal boats are sometimes painted like land vehicles. Aircraft camouflage too came to be seen as less important because of radar, and aircraft of different air forces, such as the Royal Air Force’s Lightning, were often uncamouflaged.
Researchers are developing Active camouflage or adaptive camouflage technology that is camouflage that adapts, often rapidly, to the surroundings of an object such as an animal or military vehicle. In theory, active camouflage could provide perfect concealment from visual detection. Scientific sources estimate that in five years this colour-changing technology could also be used to disguise military vehicles on the battlefield.
Active camouflage is used in several groups of animals, including reptiles on land, and cephalopod molluscs and flatfish in the sea. Animals achieve active camouflage both by color change and (among marine animals such as squid) by counter-illumination, with the use of bioluminescence.
Military counter-illumination camouflage was first investigated during World War II for marine use. More recent research has aimed to achieve crypsis by using cameras to sense the visible background, and by controlling Peltier panels or coatings that can vary their appearance.
Active camouflage may now develop using organic light-emitting diodes (OLEDs) and other technologies which allow for images to be projected onto irregularly shaped surfaces. Using visual data from a camera, an object could perhaps be camouflaged well enough to avoid detection by the human eye and optical sensors when stationary. Camouflage is weakened by motion, but active camouflage could still make moving targets more difficult to see. However, active camouflage works best in one direction at a time, requiring knowledge of the relative positions of the observer and the concealed object
Italian computer scientists Franco Zambonelli and Marco Mamei have outlined the requirements for a fabric coated with miniaturised LEDs and cameras that, by projecting the appropriate background image in all directions, could confer genuine invisibility. They say that current technologies are almost up to the task and estimate that it could cost under 500,000 euros to build a prototype.
HyperStealth patents military “Invisibility Cloak”
In 2019, HyperStealth Biotechnology Corporation, a manufacturer of camouflage uniforms used by the military, has announced that it has recently filed a patent application relating to a “Quantum Stealth Light Bending Material” which it refers to, in a nod towards Harry Potter’s famous item of clothing, as an “Invisibility Cloak”.
According to CEO and president Guy Cramer, who founded the Canadian company in 1999, “True invisibility was thought to be impossible by most physicists. Not only does the material hide a target in the visible spectrum but … it also bends in the Ultraviolet, Infrared and Shortwave Infrared while it blocks the Thermal Spectrum, making it a true ‘Broadband Invisibility Cloak’”.
In a pitch designed to highlight the potential military applications of the new technology, HyperStealth claims that by “bending” light around any given object, the material could effectively “hide” a person, a vehicle, a ship, spacecraft, even buildings. The material is said to be inexpensive and paper-thin and does not require a power source. The manufacturer has released over 100 minutes of impressive footage of the material in action.
Active Camouflage technology
Many Active camouflage prototypes have been developed with varying successes.. In 2003 researchers at the University of Tokyo under Susumu Tachi created a prototype active camouflage system using material impregnated with retroreflective glass beads. The viewer stands in front of the cloth viewing the cloth through a transparent glass plate. A video camera behind the cloth captures the background behind the cloth.
A video projector projects this image on to the glass plate which is angled so that it acts as a partial mirror reflecting a small portion of the projected light onto the cloth. The retroreflectors in the cloth reflect the image back towards the glass plate which being only weakly reflecting allows most of the retroreflected light to pass through to be seen by the viewer. The system only works when seen from a certain angle.
Phased-array optics (PAO) would implement active camouflage, not by producing a two-dimensional image of background scenery on an object, but by computational holography to produce a three-dimensional hologram of background scenery on an object to be concealed. Unlike a two-dimensional image, the holographic image would appear to be the actual scenery behind the object independent of viewer distance or view angle.
Octopus-Inspired Camouflage Sheet Developed By US, Chinese Research Team
Drawing inspiration from the color-changing capabilities of cephalopod skin, researchers have developed a new camouflage sheet capable of quickly reading its environment and adapting to mimic its surroundings. The technology, known as an optoelectronic camouflage system, is based on the ability of the octopus, squid and cuttlefish to alter their appearance to hide from predators and as a way to issue warnings. In fact, in addition to changing color, the creatures can alter the shape and texture of their skin, said National Geographic’s Ed Yong. “No man-made technology comes close” to matching the transforming talents of cephalopods, Yong said.
Rogers explained that he and his colleagues are working to develop adaptive sheets that can wrap around solid objects and change their appearance – technology that could allow military vehicles to automatically camouflage themselves, or clothing that can change its color based on current lighting conditions. Lead investigators Cunjiang Yu, assistant professor of mechanical engineering at the University of Houston, and John Rogers of the Beckman Institute for Advanced Science at the University of Illinois at Urbana-Champaign have developed a prototype that currently works in black and white, with shades of gray.
However, Yu said in a statement that the technology could be enhanced to operate in the full color spectrum. The device has a flexible skin comprised of extremely thin layers of semiconductor actuators, switching components and light sensors with inorganic reflectors and organic color-changing materials that combine to allow it to autonomously color-match its background. The three-layer design of the device was copied from the skin of the marine animals, as they have a top layer that contains the colors, a middle layer that drives the color changes, and a lower layer that senses the background patterns to be copied.
In comparison, the camouflage system is a 16-by-16 grid of squares, each of which is comprised of multiple layers, Yong explained. The top one contains heat-sensitive dye that can change color from black at room temperature to colorless at 47 degrees Celsius and back again. The next layer is a thin piece of silver used to create a bright white background, and the one below that heats the dye and controls the color. The final layer contains a light-detector in one corner, and each of the layers above it have notches removed from their corners to allow this instrument to always view the surrounding environment. The device also possesses a flexible base, allowing it to bend and contract without breaking.
“So, the light-detectors sense any incoming light, and tell the diodes in the illuminated panels to heat up,” Yong explained. “This turns the overlying dye from black to transparent. These pixels now reflects light from their silver layer, making them look white. ”
Color Changing Materials
There are a range of colour changing materials that have found use in commercial products such as ophthalmic lenses, toys (hypercolour), thermometers, and many others. These materials can be classified into two major groups – as active or passive materials depending on how the change of the colour is activated. The passive colour change materials, such as photochromic or thermochromic materials react to the changes in environmental parameters, such as ultraviolet (UV) radiation level and temperature, respectively, while active materials, can be switched on and off on demand. One group of active materials is electrochromics. They can be found in a form of a thin film or a suspension, and they range from inorganic materials (eg. tungsten oxides or vanadium oxides) to
organic materials such as viologens or conducting polymers.
Some of the electrochromic materials (inorganic and viologen based) have already been commercialised and can be found in high-end automotive dimming interior rear view mirrors (Gentex corporation) or in the Boeing 787 Dreamliner windows. However, they are limited in their switching speed and high power consumption, where to reach full contrast it takes approximately 60 seconds, and the electric potential must be applied and held to maintain the colour state. Also, viologen based electrochromics are limited to the colour
tones of blue and grey.
Another group of electrochromic materials are conducting polymers. These materials present several promising properties. They require low voltage to switch, offer colour memory effect (they retain their switched colour without a continuously applied voltage) and they have switching speeds in the range of seconds. Several chemistries of conducting polymers have been developed and they range from polyanilines, polythiophenes, polypyrroles and several other derivatives. These materials can produce a wide range of
colour tones we find closely suited to those used for military concealment.
Researchers creating active or dynamic camouflage materials that auto-matches surroundings
Cephalopods—which include octopuses, squid, and cuttlefish—are masters of disguise. These amazing sea creatures change texture, pattern and colour in milliseconds in response to new backdrops, thanks to chromatophore organs or tiny pigment sacks inside their skin. By expanding or contracting their muscles, they can control how much light bounces off these pigments and change their colours. Researchers have been trying to match their skills with varying success.
In a paper published in Feb 2018, in Advanced Optical Materials, Deravi’s group describes its work in isolating the pigment granules within these organs to better understand their role in color change. The researchers discovered these granules have remarkable optical qualities and used them to make thin films and fibers that could be incorporated into textiles, flexible displays, and future color-changing devices. Deravi’s lab collaborated with the U.S. Army Natick Soldier Research, Development, and Engineering Center for the study.
By removing individual pigment particles from the squid, Deravi was able to explore the breadth of their capabilities as static materials. One particle is only 500 nanometers in size, which is 150 times smaller than the diameter of a human hair. Deravi’s team layered and reorganized the particles and found they could produce an expansive color pallet. “We’re showing these pigments are a powerful tool that can produce ultra-thin films that are really rich in colors,” Deravi said.
Her team also discovered the pigments can scatter both visible and infrared light. This enhances brightness and light absorption and affects how a final color is perceived. And when Deravi engineered a system that included a mirror—mimicking the layout of organs that squids have naturally—she was able to further enhance the perceived color through scattering light through and off the granules. This process could potentially be replicated on functional materials like solar cells to increase the absorption of sunlight, Deravi said.
“From a scientific and technical engineering perspective, understanding how light scattering affects color is very important, and this is an exciting new development in the field of optics in biology,” said Richard Osgood, a collaborator from the U.S. Army Natick Soldier Research, Development, and Engineering Center. “This is an unusual harnessing of optics and physics knowledge in scattering to understand biological systems.”
In 2016, Scientists University of Illinois and the Massachusetts Institute of Technology (MIT) made significant steps towards mimicking this process, which they call visual appearance modulation, with a new material. One side of the material contains thousands of tiny light-sensitive cells that can detect surrounding colours. Electrical signals then trigger the top layer to imitate those colours by using heat-sensitive dyes.
Engineering professor Xuanhe Zhao, at MIT, said: ‘I have high hopes for its use in military camouflage. At the moment the military spends millions of dollars developing new camouflage patterns but they’re all static right now, they don’t change. If you put a pattern designed for the forest into the desert, it is not going to function.
‘Dynamic camouflage would allow soldiers and their vehicles to adapt to their surroundings instantly.’ The tests by 3 Rifles and American troops of camouflage material that is ready for use now against enemies such as Islamic State and the Taliban took place earlier this year at the US Army’s centre for experimental warfare techniques at Fort Benning, Georgia. During the trials, British snipers used Vatec – which can be moulded into shapes to match mountainous terrain – to build hideaways on a mock battlefield. In 2014, Scientists from the Massachusetts Institute of Technology (MIT) and Duke University in the US reported to have developed a stretchy, skin-like synthetic material that takes us a step closer to invisbility-cloak-like camouflage.
The material was inspired by cephalopods, the class of animals containing the very-well-camouflaged octopuses, squids and cuttlefish. The new material acts in a similar way, as Sarah Zhang explains for Gizmodo. The polymer has dyes embedded in it, and when voltage is applied to the material it causes the polymer to crease up, changing its texture and colour. This means it can immediately become fluorescent red or bumpy, and even change its pattern, as shown in the images above.
“The texturing and deformation of the elastomer [the polymer that makes up the material] further activates special mechanically responsive molecules embedded in the elastomer, which causes it to fluoresce or change colour in response to voltage changes,” said Stephen Craig, one of the lead researchers from Duke University, in a press release. “Once you release the voltage, both the elastomer and the molecules return to their relaxed state — like the cephalopod skin with muscles relaxed.”
‘Invisibility’ Material Offers Thermal Camouflage
Gorodetsky led the development of the adaptive camouflage materials that change their infrared reflectance on demand, enabling the surface to acquire desired – and potentially deceiving – thermal signatures when visualized under an infrared camera. After being stretched or electrically triggered, the material’s thin swatches quickly change heat reflectance, smoothing or wrinkling their surfaces in under a second. The modulation of apparent temperatures enables an invisibility to infrared night-vision tools. “It goes from wrinkled and dull to smooth and shiny, essentially changing the way it reflects the heat,” said Gorodetsky of the material.
“Essentially, you start out with a surface that’s wrinkled. The wrinkles are tens to hundreds of microns scale, and then you flatten that surface. In those two states is where you have the differences in how the material reflects heat or infrared light.” In the flattened state, the material reflects the heat right back at you. In the wrinkled state, the material scatters the heat, so it doesn’t come right back at the source, or at a camera, that’s looking at heat reflection. Being able to go between those two states is what gives these adaptive properties to the material. When you look at that surface under an infrared camera, those two states will look very different and they’ll have very different apparent temperatures. That effectively lets the material reappear and disappear under an infrared camera.
The camouflage aspect is one, for example, for security applications, but there are many common technologies that rely on controlling thermal radiation. For example, you could create windows on buildings that in one state might reflect heat, but in another state might let it in to maintain the temperature of the building.
The robot uses nanowires that helps it change colour instantly, reported in August 2021
A group of researchers from South Korea have created a robot that is able to change its colour like a chameleon — known to possess the remarkable ability to adjust the colour of its skin to match the surface it is on and blend with the surroundings. The breakthrough research has paved the way for a new high-resolution artificial camouflage technology that can be widely used, including for military and espionage purposes. It can increase the survivability of military equipment and personnel from enemy fires. Previous attempts at artificial camouflage relied on devices with tiny channels to control the flow of fluids inside, but this project took a fully electric approach.
The researchers said that they used colour sensors, nanowire wires, and thermochromic materials —change colour when heated or cooled — to create multiple skin patterns that allowed the robot to change colours almost instantly. The study has been published in the journal Nature Communications. Seung Hwan Ko, a professor at Seoul National University and one of the authors of the study, told MIT Technology Review that the most challenging part was getting the colour transition speeded up to create an appearance of natural behaviour. Here, nanowires, which heat up quickly, were useful. These wires would warm the artificial skin very fast to let the robotic skin change colour.
The nanowires also were useful in creating simple patterns to give shape to the chameleon robot. However, as the technology is dependent on colour, it doesn’t work as well in extreme cold. Also, the development of an artificial camouflage at a complete device level remains a vastly challenging task. But Hwan Ko hopes the research will have a wider impact, more than just military uses, like in the fields of transportation, beauty, and fashion. This technology can help future cars to adapt their colours to stand out or even we can see colour-changing clothes.