Octopuses can change color to match their surroundings
Nikos Stavrinidis/500px/Getty Images
Inks that change color when exposed to light, much like octopuses change color to match their surroundings, may one day be used for automatic camouflage.
Most color-changing inks and materials use chemical reactions, which can be unstable and difficult to control. Instead, octopuses use special muscles to push particles of colored ink to the surface of their skin.
Now, Jinyao Tang of the University of Hong Kong and his colleagues have similarly developed an ink that can display different colors by moving dye particles according to exposure. The ink consists of particles of titanium dioxide, each containing different dyes and different photoreactions, placed in solution.
When light from a standard projector hits the ink-laden material, a chemical gradient causes some ink particles to rise to the surface and others to fall. “Like oil and water, [the particles] It separates and floats to the top because it’s colored,” says Tan. “You can change the colors accordingly, mimicking the colors you’re actually shooting.”
Tan and his team formulated inks in the three colors used in the common CMY color scheme: cyan, magenta, and yellow. The improved projector was then used to display semi-permanent images, such as a child’s drawing with ink. They found the images to be stable for about 30 minutes before the inks were remixed.
With further research, we may one day be able to use this for automatic camouflage. “In the woods, everything is green, so the clothes and materials will turn green when they receive that kind of green light from their surroundings,” Tan says. “When you sail through the desert, everything turns yellow, [the ink] It becomes a yellowish color. ”
However, for use in such environments, Tang says, the desired color must be maintained for at least 30 minutes before remixing the ink.
Because the ink rearranges itself without electricity, it could be used in a wide range of applications, such as updating signs without requiring large amounts of energy, said James Hallett of the University of Reading, UK. “[The ink] There are no electrodes inside, just an external source to change colors and set them in place,” he says. “This idea of adaptive octopus camouflage makes it much more practical than other methods.”
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