When light strikes a photodetector, it sends a signal that drives current into the diode above it; the diode heats up, causing the black dye to turn transparent. This lets the white layer of silver show through. As the pattern of ambient light changes, the array of pixels match the pattern of light striking the structure.
The system, which works in a manner similar to the skin of cephalopods like the cuttlefish, grew out of the research of Roger Hanlon, a biologist at Brown University and the Marine Biological Laboratory at Woods Hole, Mass. Hanlon, Rogers, and their colleagues describe the work in the current issue of Proceedings of the National Academies of Science.
The work was sponsored by the U.S. Navy, which has an obvious interest in camouflage, but Rogers says there could be a range of industrial and consumer applications, including mood lighting and sensors that change color based on exposure to ultraviolet light.
Though the team worked with black and white to demonstrate the concept, Rogers says the technique could also be used to display colors - and might incorporate actuators or even a camera. "We view it as sort of a general set of engineering approaches," Rogers says.