3D printing is all the rage in so many industries right now. From clothing to defense, in 2018 many companies are taking advantage of 3D printing. But 3D printing has not been perfected yet. There are still a few drawbacks. One of these drawbacks: when an object is printed, it is final. If someone wanted to change the color of a 3D printed object, they would have to print an entirely new one. If a company wanted to create a patterned phone case, but they wanted to change the color of part of the pattern after the print, they need to fire up a reprint.

This is MIT professor Stefanie Mueller, pictured in her lab. (Source: Jason Dorfman, MIT CSAIL)

But researchers from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) are developing a way to change the color of 3D printed objects that have already been printed. The project, called “ColorFab,” is a method that allows users to repeatedly change the color of pre-fabricated 3D printed objects.

In order to develop color-changing objects, the researchers created a 3D printer ink that shifts color when it is exposed to sunlight. Using this ink, they were able to recolor an object in 20 minutes. The team hopes to decrease how long this takes as they further develop the product.

Right now, the material is only used on plastics and other common materials used in 3D printing. But eventually, it could be used to instantly change the color of other items like clothing.

"Largely speaking, people are consuming a lot more now than twenty years ago, and they're creating a lot of waste," says MIT professor Stefanie Mueller, who co-wrote the new paper about the system. "By changing an object's color, you don't have to create a whole new object every time."

Other color-changing systems were developed in the past, but these systems' capabilities were limited. They could only develop items in single-colors for 2D items.

The research team wanted to go further than 2D items. For the first tests, users uploaded a 3D model into the ColorFab interface. From there they could pick a color and pattern they liked and print.

Changing the color of these objects requires UV light. UV light activates desired colors and visible light deactivates other colors. A UV light was used to change pixels from transparent to colors, and a regular office projector was used to change the colors back to transparent.

The custom ink is made out of a base dye, photo-initiator and light-adaptable dyes. The light-adaptable dyes bring out the base color dye and the photo-initiator dye allows the base dye to harden in the 3D printing process.

ColorFab was tested under three conditions: recoloring time, precision and how quickly the color decayed. The full recoloring took 23 minutes, but the researchers plan on speeding up this process by adding light-adaptable dye to the ink and using a more powerful light.

The light-changing colors tend to appear slightly grainy, according to the researchers. This could be improved by activating colors closer together.

3D printing could be further popularized if people were able to quickly change the colors to do things like match accessories to their outfit depending on the colors. Retail stores could take advantage of this development by allowing customers to customize their purchases in real time.

"This is the first 3-D printable photochromic system that has a complete printing and recoloring process that's relatively easy for users," says postdoc Parinya Punpongsanon. "It's a big step for 3-D-printing to be able to dynamically update the printed object after fabrication in a cost-effective manner."

ColorFab could be a huge development for 3D printing. 3D printing is constantly growing, but the development of color-changing material could bring it even more into the mainstream.