A research team from the University of California at Irvine has developed “squid-inspired invisibility stickers” that allow soldiers to disguise themselves and hide from active infrared visualization.
Squids, as ideal camouflage artists, perfectly blend with their background to hide themselves from unsuspecting prey. The scientists have made use of a protein involved in this camouflage mechanism to design these stickers.
Soldiers wear uniforms with the familiar green and brown camouflage patterns to blend into foliage during the day, but under low light and at night, they’re still vulnerable to infrared detection. We’ve developed stickers for use as a thin, flexible layer of camo with the potential to take on a pattern that will better match the soldiers’ infrared reflectance to their background and hide them from active infrared visualization.
Alon Gorodetsky, Ph.D.
Gorodetsky had taken inspiration from squid skin that features atypical cells called iridocytes. These cells are composed of platelets or layers made of reflectin proteins. The squid changes the spacing and thickness of the layers through a biochemical cascade mechanism. As a result, the pattern of light reflection by the cells and hence the coloration of the skin also get changed.
The scientists produced reflectin protein by coaxing bacteria and the resulting protein was used to coat a hard substrate. The protein film has to be subjected to a trigger in order to induce light-reflecting and structural changes like iridocytes. Earlier studies have revealed the use of acetic acid vapors to make the film swell and disappear upon visualization through an infrared camera. However, this method may not be suitable for soldiers in the battlefield.
What we were doing was the equivalent of bathing the film in acetic acid vapors — essentially exposing it to concentrated vinegar. That is not practical for real-life use.
Alon Gorodetsky, Ph.D.
Therefore, Gorodetsky has laid the reflectin films on conformable polymer substrates, resulting in a sticky tape that can be found in any household. The tape is capable of adhering to any surface including cloth uniforms. Thus, the appearance of the film under infrared camera can be altered using a mechanical trigger i.e. stretching, which is realistic for military operations.
The invisibility stickers are yet to be introduced in the commercial market. Gorodetsky envisage that this technology holds promise in camouflage operations in future, enabling the soldiers to carry the stickers in their pockets to cover their uniforms when required.
We’re going after something that’s inexpensive and completely disposable. You take out this protein-coated tape, you use it quickly to make an appropriate camouflage pattern on the fly, then you take it off and throw it away.
Alon Gorodetsky, Ph.D
Gorodetsky stated that the technology has some major limitations, and the team has to find a solution to increase the stickers' brightness. In addition, they will have to make multiple stickers to respond in the same manner and at the same time to ensure an adaptive camouflage system.
Gorodetsky is further working on the methods of making more versatile stickers. As the existing materials are capable of reflecting near-infrared light, the team is on the verge of producing variants that can operate in mid- and far-infrared wavelengths. The variants could have potential applications in thwarting thermal infrared imaging and in clothing to retain or release body heat.
Gorodetsky’s lab scientists in association with Francesco Tombola and Lisa Flanagan from the UCI School of Medicine have proven that the reflectin protein stimulates cell growth, which could have used in new bioelectronic devices and in developing “living” semi-artificial squid skin.
The work has been presented at the 249th National Meeting & Exposition of the American Chemical Society (ACS).