Camouflage Tech Copies Cuttlefish's Disappearing Act
Scientists have created digital pixels that change color to match the pattern of light striking them.
Octupodes and cuttlefish have a remarkable ability to change their appearance, producing colors and patterns in their skin that allow them to disappear into the background. Now a team of scientists says they've engineered an approach to camouflage that's inspired by the way these sea creatures work.
"I think we've put together the key elements that are needed," says John Rogers, head of materials research the University of Illinois at Urbana-Champaign.
The adaptive optoelectronic camouflage system, which Rogers developed with scientists from Illinois, Texas and China, consists of several components piled on top of one another in very thin layers and divided up into pixels.
The top layer contains a kind of dye that is normally black but becomes transparent with a small increase in temperature. Beneath that is a layer of white reflective silver. Next down is an array of silicon diodes that heat up when current runs through them. Separated from that layer by a sheet of silicone lies an array of ultrathin silicon photodetectors on a transparent polymer substrate.
When light strikes a photodetector, it sends a signal that drives current into the diode above it; the diode heats up, causing the black dye to turn transparent. This lets the white layer of silver show through. As the pattern of ambient light changes, the array of pixels match the pattern of light striking the structure.
The system, which works in a manner similar to the skin of cephalopods like the cuttlefish, grew out of the research of Roger Hanlon, a biologist at Brown University and the Marine Biological Laboratory at Woods Hole, Mass. Hanlon, Rogers, and their colleagues describe the work in the current issue of Proceedings of the National Academies of Science.
The work was sponsored by the U.S. Navy, which has an obvious interest in camouflage, but Rogers says there could be a range of industrial and consumer applications, including mood lighting and sensors that change color based on exposure to ultraviolet light.
Though the team worked with black and white to demonstrate the concept, Rogers says the technique could also be used to display colors - and might incorporate actuators or even a camera. "We view it as sort of a general set of engineering approaches," Rogers says.
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The skin of cephalopods like the cuttlefish has the remarkable ability to instantly change colors and patterns.
A star at the Monterey Bay Aquarium's new exhibit "Tentacles: The Astounding Lives of Octopuses, Squid and Cuttlefishes" is the flapjack octopus. The name was inspired by its flattened appearance. It is among the most anatomically compressed species in the world. The character "Pearl" in the Disney/Pixar film "Finding Nemo" was based on a flapjack octopus.
Flamboyant cuttlefish are colorful, and deadly. Its muscle tissue is highly toxic, making it one of only a handful of cephalopods known to be toxic. They can change color to help them sneak up on prey or to scare predators.
"Dwarf squid are the smallest squid species in the world," Monterey Bay Aquarium aquarist Chris Payne told Discovery News. In addition to this petite creature, the new exhibit features a dozen living exhibits showcasing rotating appearances by up to two dozen species -- many never exhibited before.
On the other side of the size spectrum is the giant Pacific octopus. It is the largest octopus species in the world. Adults can weigh hundreds of pounds and have an arm span of more than 12 feet. The giant Pacific octopus is a master of disguise, like many other cephalopods. It can change both its skin texture and color in order to defend itself.
A cuttlefish moves by undulating a delicate fringe that runs along its entire body, but for a quick getaway it expels a forceful stream of water through its siphon, according to Monterey Bay Aquarium aquarist Bret Grasse. When threatened, cuttlefish can produce a cloud of ink called sepia. Long ago, this dark-brown ink was used for writing and drawing.
These are bigfin reef squid eggs, which were collected from the northern Indo Pacific, Monterey Bay Aquarium aquarist Alicia Bitondo told Discovery News. She added, "There are about 300 egg pods in this tank, with about 6 embryos per pod." She and others at the aquarium are breeding the species through multiple generations as one of the featured exhibit animals in the new special exhibition.
Unlike other species of octopus, the day octopus is more active in the daytime than at night. The day octopus originally arrived at the aquarium via a direct flight from Honolulu, Hawaii, since it is native to waters there. It lives in East African waters as well. The large, almost 3-foot-long predators are short-lived. They survive just one year, on average, and breed only once. Cephalopods, in general, don't live for very long, which is why the aquarium is cultivating cephalopods during the exhibition. "These are all short-lived animals," Monterey Bay Aquarium special exhibits coordinator Jennifer Dreyer said. "Many are species that have never been exhibited for very long by any of our colleagues, or raised through their entire lifecycle. This is definitely a first for any aquarium."
Up to 50 nautiluses will occupy a huge exhibit, with a ceiling-to-floor viewing window. These animals like to hide away safely in their protective shells. Many other cephalopods are equally evasive, desiring to blend into their surroundings for protection and to surprise prey. This can make putting them on display challenging. As Bitondo said, "We're trying to display something that doesn’t want to be seen."
A red octopus' normal color is red or reddish brown, but like many other cephalopods it can change quickly -- in a fraction of a second -- to yellow, brown, white, red or a variety of mottled colors. The red octopus is thought to be a clever animal. In 2012, a tiny juvenile red octopus hitchhiked into the Monterey Bay Aquarium on a sponge. It hid in one of the exhibits for a year before being discovered walking across the aquarium's floor in the middle of the night. The discovery helped to explain why so many crabs had gone missing during that period of time. They had gone into the red octopus's tummy. The then out-of-place octopus was eventually released into Monterey Bay, but the species will be represented by others in the new exhibition.
The wonderpus octopus is native to the Indo Pacific region. Each individual has unique white markings on its head, allowing scientists to track individual specimens. It, along with other cephalopods, will be part of the new "Tentacles" exhibit at the Monterey Bay Aquarium. The exhibit opens April 12 and runs through Labor Day of 2016.