We've already heard about two different studies in which scientists are developing camouflage systems inspired by squids' color-changing skin. If they're successful, the result could be military clothing that can change its coloration to match the environment. It's an intriguing idea, although it presumably still wouldn't allow soldiers to avoid detection by infrared cameras at night. Now, however, researchers from the University of California at Irvine are developed a stick-on covering that could let them do so.
Squids are able to rapidly change color thanks to cells in their skin known as iridocytes. These contain platelets made of a protein called reflectin. By adjusting the thickness and spacing of these platelets, the animals are able to change the manner in which their skin reflects light.
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Led by Dr. Alon Gorodetsky, the UC Irvine team got E. coli bacteria to produce reflectin. They then coated a hard surface with a film of the protein, and got that film to swell by exposing it to acetic acid (concentrated vinegar) vapors. As a result, the film-coated surface reflected infrared light in a manner similar to its background, rendering it "invisible" to an infrared camera.
Soldiers probably won't want to douse themselves in vinegar, though. Given that fact, the team proceeded to incorporate reflectin into thin, flexible, adhesive-backed polymer sheets – stickers, essentially – that are activated by being stretched as opposed to acetic acid exposure. The polymer can be stuck to a variety of surfaces, including clothing.
Some work still needs to be done, including increasing the reflective brightness of the material, and getting multiple sheets of it to all change in the same way at the same time. Additionally, it so far only works on visible and near-infrared light.
Ultimately, however, Gorodetsky hopes that soldiers could one day carry rolls of the inexpensive stickers with them while on maneuvers. They could just apply them as needed, then peel them off and discard them afterwards. The material's reflective quality may also allow for its use in clothing that can reflect the wearer's body heat back in or let it escape, depending on the environment.
Source: American Chemical Society