At first glance, the thumbnail-size grids of 256 minuscule black squares seem to have nothing to do with the octopus, squid and cuttlefish that inspired them. But these high-tech microconstructions of polymers, semiconductors, light sensors and heating elements are what you get when scientists attempt to replicate the camouflaging ability of the animal world.
One of the goals of the scientists’ work, which explains the Navy’s financial support of the project, is to invent synthetic skins that can recast their textures, colors and patterns to match their surroundings — match them well enough that the skins and what’s underneath them essentially disappear.
For millions of years, hiding has been a primary means of survival for soft, gushy and often defenseless cephalopods, which predators find so alluring that squid and related creatures are a bait of choice for fishermen. Engineers can learn a lot from these masters of deception.
“The power of evolution is spectacular,” says John Rogers, a materials scientist at the University of Illinois at Urbana-Champaign who is part of a multi-institutional team developing high-tech camouflage. “We are taking inspiration from nature to build devices that can respond and adapt to the lighting and coloration of whatever environment they are in.” The scientists envision paints and fabrics that can change their patterns swiftly, even entire naval vessels that can blend into their surroundings with octopus-inspired camo skins.
The natural world has a huge array of camouflage tactics that involve shape, edges, coloration, contrast and textures of anatomy. Insects known as walking sticks, for instance, look like the twigs where they live, a technique referred to as background matching. The high-contrast, black and white pattern of a bear in a tree or an orca in the water, taps into the light and shadows of a forest or ocean in ways that disrupt the perceived outline of the animals’ bodies.
You cannot connect the dots to recognize these animals, says Roger Hanlon of the Marine Biological Laboratory in Woods Hole, Mass., who for four decades has focused on the even more sophisticated camouflage abilities of cephalopods to all but disappear into whatever setting they find themselves.
“The speed of change and diversity of patterns in these animals appears to be unmatched by any other animal group we know of,” including even chameleons, Hanlon says. For the past few years, Rogers has been working with Hanlon and others to develop extreme camouflage in synthetic materials.
In the topmost skin layer of stealthy cephalopods are millions of tiny organs, which are like minuscule bags of paint that can expand or ball up.Using webs of tiny muscles, cephalopods can change the shape of these organs, called chromatophores, to repaint their skin in less than a second. Underneath, a second skin layer harbors cells, called iridiphores, rich in slabs of protein that behave like bicycle reflectors. The skin’s bottom layer is a carpet of white cells, or leucophores, which amount to a bright canvas on which the color magic unfolding in the two upper layers can stand out.
With those biological systems as models, Rogers and his colleagues came up with rudimentary patches of synthetic cephalopod skin.
Up close, each high-tech patch looks like a grid of poppy-seed-size black squares. Each square is topped with dye that toggles between white and black with a shot of heat. Just underneath the dye layer is a film of reflective silver particles that shunt light coming into the skin back up through the dye-laden spots. Next comes a grid of minuscule heating elements whose temperature the researchers can control to trigger the black-to-white or white-to-black shift in the spots of dye.
Rogers’s group in Illinois lays these three layers atop a plastic sheet made of the same stuff as contact lenses. Underneath goes a fifth layer: a set of sensors that detect light and dark patterns in the environment and send that information to a computer, which uses the heating elements to replicate the sensor-detected pattern in the overlying dye-bearing squares.
While far more basic than what’s found in nature, the researchers have shown that this computer-controlled material can react like an octopus to visual cues in the environment. For example, when the researchers shine lights in a pattern that forms the letters U, O, and I — for University of Illinois — the synthetic skin switches from all-black pixels to a black-and-white “UOI” pattern. This is not cephalopod camo, but Rogers says these early results suggest that engineers will in a few years be able to match nature’s versatile all-color camouflage wizardry.
Military applications will come first, predicts Thomas Cronin, a biologist at the University of Maryland Baltimore County who is part of the research community with octopus-to-gadget ambitions. “When a machine or person moves to a different environment or background, these camouflage systems could automatically reduce the level of detectability to any imaging system,” he says.
“They hope to reach beyond the limited set of materials biology uses and bring about new materials with exotic properties to obtain performance unachievable in nature,” remarks Mark Spector, a program officer with the Office of Naval Research, referring to Rogers, Hanlon and other camo researchers supported by ONR. Rogers, for one, envisions a world with octopus camouflage ability all over it.
“This is a starting point,” he says. “I am thinking about surfaces whose colors are programmable and adaptive to what is going on.” A textile artist at the Art Institute of Chicago interested in futuristic fabrics has been in touch, Rogers notes. He then ticks off a bunch of things — cars, toys, displays, even living room walls — that he imagines could be designed with astounding morphing surfaces, from smooth to bumpy or woven textured, like wicker.
Amato, a writer based in Silver Spring, runs the D.C. Science Cafe at Busboys and Poets.