Color-changing tattoos or make-up that change your palettes in the blink of an eye: The limit that the metaphorical sky represents today can be found in nature in the form of chameleons and technology with the PhotoChromeleon system, developed by the Science Lab team. Computing and Artificial Intelligence of the Massachusetts Institute of Technology (CSAIL / MIT).
PhotoChromeleon is based on a reprogrammable ink that is actually a mixture of cyan, magenta, and yellow (CMY system) photochromic dyes. It is an evolution of ColorMod, which uses a 3D printer to manufacture items with the same color-changing capability. However, the project had limitations, such as a small color palette and low resolution results. The new sprayable ink eliminates the need to print 3D pixels individually.
To get to PhotoChromeleon, the team used three lights of different wavelengths to eliminate each primary color separately, ie by activating and deactivating the corresponding light sources. In the case of blue light, for example, it will be absorbed by the yellow dye, remaining visible magenta and cyan, resulting in blue. In the case of green light, magenta will absorb it, while yellow and cyan will remain, resulting in a green color.
The process is reversible, meaning it can be repeated infinitely. After the light turns on colors, the new pattern appears. To erase it, just use the UV light and start all over again. The new paint can be applied to anything – the team tested the system on a car, a phone case, a pair of shoes, and a small toy chameleon. Depending on the object tested, the color change took 15 to 40 minutes. All patterns obtained had high resolution and could be deleted.
Although PhotoChromeleon offers a much wider range of colors than its predecessor, not all shades were represented in photochromic dyes. For example, an ideal combination for magenta or cyan has not yet been achieved. It was then necessary to use the dye that was closest to the desired color.