MIT Researchers Create Color-Shifting Ink for 3D Printers

Most things that are 3D printed are still just a single color of plastic, but some more fancy printers might be able to print with a few colors. A new printing technology designed by MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) has the potential to add significantly more colors to 3D printing without the need for additional print heads. Researchers there have developed color-shifting dyes for 3D printed objects. Shine some light on the object, and it changes color.

The project started from a fashion perspective. MIT professor Stefanie Mueller, who led the research, was concerned about the wasteful state of consumerism. People sometimes buy new things just because they get tired of the old one. She wondered if there wasn’t some way to update materials without buying something new, and the custom 3D printing dye dubbed ColorFab is what the team managed to come up with.

ColorFab isn’t just the dye — it’s an entire system for customizing objects after they’ve been printed. In the video below, a rather large and gaudy ring was used to show off the technique. Using the ColorFab 3D interface, users can design the object they want and print it in about 20 minutes. Most of the layers are normal 3D printing plastic medium, but the top layer contains the ColorFab dye.

The ColorFab printing medium contains a base dye, a photo catalyst, and a color-sensitive “photochromic” ink. When bombarded with UV light of the correct frequency, the ink shifts colors. You can even control which colors with the specific wavelengths. Past versions of this process could only change to a single pre-defined color, and then the color would only last as long as the UV light source was turned on. The coloring process takes about 20 minutes, but the color remains after you shut the UV off.

The ColorFab software lets users choose which “pixels” on the object they want to change. You could spell out words or draw simple pictures on ColorFab objects, but they won’t last forever. Visible light resets the dye, so it’ll fade over time. The CSAIL team measured how long it would take for the ink to reset from ambient light, finding it degraded conscientiously, but was still visible after 30 days. A more intense light source can be used to manually reset the dye in a few minutes so you can re-color it. The team hopes to make ColorFab faster and more efficient to make it a viable product.