Chameleons can change their colors thanks to photonic crystals in their skin. As they tighten or relax the muscles, the light is reflected in a different pattern, resulting in a change of color. The problem with synthetic color change skin lies in the hydrogel in which the photonic crystals are packed: After expanding and contracting, the large amount of crystals would cause the medium to seize. Khalid Salaita and his colleagues have solved this problem by concluding that less is more.
The team looked at past video clips of chameleons' phase-shifting skin and realized that the reptiles have fewer skin cells with photonic crystals than previously thought. By packing fewer photonic crystals into a thin layer of hydrogel and then placing that disc on a larger layer of colorless hydrogel, the smart skin can be expanded and contracted effortlessly. When the temperature changes or the sunlight hits the surface, the material changes color.
ACS Nano a peer reviewed journal focused on nanotechnology where this study was published, noting that smart skin may have applications in camouflage, signaling and forgery. MIT's color-changing ink can meanwhile allow users to change the patterns and colors of their shoes, cars and more. Choosing a color for an expensive gadget like a smartphone can be a stressful one; You will have to live with that choice for several years. But with smart skin, we can eventually change the colors of our gadgets as often as we replace our wallpapers.