From sci-fi suits to wizarding worlds, invisibility cloaks have appeared in folklore to fantastical movies for decades and captured the imagination of all who come across them. A wearable device that allows the user to completely fade from sight has been the dream of mischievous children and national militaries alike, but so far no practical options have surfaced. A Canadian company came close in 2019 when it developed a shield that renders anything behind it difficult to see, but true wearable invisibility is an entirely different ball game.
Rising to the challenge, a team of researchers from Seoul National University and Hanyang University have created an artificial skin that renders the wearer functionally invisible in the visible-to-infrared spectrum of light. Inspired by cephalopods like octopuses and squid, the material is controlled by heat to change the colors on a surface, like skin, to cloak anything behind it. They published their creation in the journal Advanced Functional Materials in July.
“In this study, a multispectral imperceptible skin that enables human skin to actively blend into the background both in the IR-visible integrated spectrum only by simple temperature control with a flexible bi-functional device (active cooling and heating) is developed,” state the authors in the paper.
Impressively, the material doesn’t stop at making you invisible to the naked eye. By strictly controlling the surface temperature, it also renders the user invisible to infrared cameras. With such a material desired by military personnel for covert operations, the authors expect this work to “contribute to the development of next-generation soft covert military wearables”.
The material is an advancement on thermochromic materials, which already see a lot of mainstream use. If you have ever purchased a mug that changes color when a hot drink is added you have seen a thermochromic material in action. In essence, these materials change color in response to high or low temperatures. If scientists could create a material that has three colors (red, green, and blue) in response to three temperatures, then theoretically the material would work in a similar way to a TV, with RGB pixels creating an image. Unfortunately, current thermochromic materials suffer from one fatal flaw that prevents use in invisibility devices – they change color very, very slowly.
The researchers wanted to see whether manipulating an electrical current within a layer just beneath the thermochromic material could speed up the color-changing process. After creating a multi-layer material with electrodes and a conductive layer, the researchers saw a much faster response in color changing. In a similar way to how an octopus can change its skin to match the surroundings, the artificial skin could change color based on temperature manipulation.
Now, the researchers hope the work can be built upon in the pursuit of complete invisibility. This study serves as a proof-of-concept and still needs significant refining to be practical in real-world applications, but it represents a significant leap in wearable invisibility materials.
[H/T: Defense One]