Chameleon-inspired robot skin changes colors instantly

Chameleons have long been a symbol of adaptation because of their ability to adjust their iridophores—a special layer of cells under the skin—to blend in with their surroundings. In a new study published today in Nature Communications, researchers from South Korea have created a robot chameleon capable of imitating its biological counterpart, paving the way for new artificial camouflage technology. Using color sensors, tiny heaters made of silver nanowires, and thermochromic materials, which change color when exposed to different temperatures, the team was able to re-create multiple high-resolution skin patterns that allowed the robot to transition between colors almost instantly. Previous ventures into artificial camouflage have often relied on microfluidic devices, which use tiny channels to control the flow of fluids inside, but this project takes a fully electric approach. Seung Hwan Ko, a professor of thermal engineering at Seoul National University and one of the authors of the study, says the most challenging part was getting the color transition up to nature’s speed. Using the nanowire heaters, which heat up very fast, helped solve that problem: the artificial skin warmed quickly enough to change color at a similar speed to the real animal’s. Related StoryThe US Army is creating robots that can follow ordersFor robots to be useful teammates, they need to be able to understand what they’re told to do—and execute it with minimal supervision. “[Building] a first prototype was very slow,” says Hwan Ko. The first step was determining if the robot would be modeled after a vertebrate—an animal with a backbone—or an invertebrate, like a squid or an octopus. Since an invertebrate model could offer more freedom of movement, the team initially made plans to mimic the octopus, but Hwan Ko says that idea proved “too ambitious.” After fiddling with different designs and material structures, the team finally decided to tackle the simpler form of the chameleon itself. By shaping the nanowires into simple patterns composed of dots, lines, or scale shapes, they were able to create the complex effect shown in this video. Although previous research into artificial camouflage has often been tagged for military use, Hwan Ko hopes their work will have a wider impact, particularly in the fields of transportation, beauty, and fashion. Future applications could include cars that adapt their colors to stand out, and even color-changing cloth. “This chameleon skin, the surface, basically is a kind of display,” he says. “It can be used for a soft or stretchable or flexible display.” Because the technology is temperature-dependent, though, it doesn’t work as well in extreme cold, which can make it harder for the faux chameleon to realize the full spectrum of color. Ramses Martinez, an assistant professor at Purdue University who also studies bio-inspired robotics, says that translating other biologically inspired systems into new technologies could lead to more possibilities, including systems that help locate survivors after an earthquake.