A research team in China has developed a coating using nano-size cells that can be controlled to inflate or deflate, and, as a result, deflect visible light in different wavelengths. The result is painted surfaces that act like chameleons and change color to match environmental shifts. The process uses polydispersive photonic micro-beads responsive to metal ion-responsive photonic colloidal crystalline (PCC) microspheric material. This works along with the convenient, reversible switching of photonic diffraction properties by the redox reaction of copper in a simple electrochemical cell. The PCC micro-beads were fabricated from the orderly three-dimensional packing of core-shell nanoparticles with hydrogel coatings laden with anionic phosphate functionalities. The cells change color in response to the chemical reaction, and then back to their original color, without losing any of the color quality. Lead researcher Du Xuemin, from the Shenzhen Institutes of Advanced Technology, said, “Imagine the fun of instantly changing the color of everything, from the wall to the floor to the furniture, just by swiping a smartphone. Our paint will make these dreams come true.” The biggest challenge, Du said, was making the nano-cells. The diameter of each is only several-hundredths of the diameter of a typical human hair. Each cell’s uneven surface also has to be controlled precisely or the desired colors won’t come through. Now that those issues are resolved, the team is producing a few dozen liters of the paint daily. He expects to see commercial quantties of the paint available within three years. www.sciencedirect.com/science/article/pii/S092540051530424X