This New Ink Lets You Change the Color of 3D-Printed Objects

Most retail shoppers know someone (or are someone) like this; they go into a favorite store, find a shirt, watch or purse they love, and proceed to buy it in three different colors to match with more outfits. Now, thanks to a 3-D printing innovation from MIT, those chronic spenders might save more money, time, and resources by investing in accessories with color-changing ink. 

The MIT team created an ink that would allow owners to change the color of an accessory on demand in just minutes. The process is called ColorFab -- a way to change color post-fabrication. 

"Largely speaking, people are consuming a lot more now than 20 years ago, and they’re creating a lot of waste," says Stefanie Mueller, the X-Consortium Career Development Assistant Professor in the departments of Electrical Engineering and Computer Science and Mechanical Engineering. "By changing an object’s color, you don’t have to create a whole new object every time."

In fact, this printing innovation would cut down on waste from accessories retailers like Claire's and Charming Charlie who focus much of their store inventory on making different variations of the exact same style of product. (Charming Charlie even categorizes its entire store based on color before any other factor.)

Color changing clothes could be next

The project is currently focused on changing the color of plastics and other common 3-D printing materials. However, the researchers hope to one day expand into other textiles and allow people to change the color of their clothes. 

In order to make the ink, the MIT team made a hardware/software workflow. They used the unique interface developed for ColorFab to allow users to upload a 3-D model, pick color patterns, and then print the object. After the object has been printed, the team uses UV light to activate the unique colors that had been "hidden" and visible light to deactivate the other colors. (Or, as the research team admitted, they use UV light to change pixels from transparent to colored and a normal old office projector to turn off certain colors.)

"I'm hopeful that in the future this sort of system could help encourage consumers to be more mindful about their purchases and maybe buy just one of something instead of buying it in every single color," Mueller said in an interview. 

But what exactly goes into the dye? The custom ink is based on photoinitiators and light-adaptable (or photochromic) dyes, the team reported. Those photochromic dyes bring out the main color and the photoinitiator allows the base dye to harden up during the printing process. 

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"Appearance adaptivity in general is always a superior feature to have, and we’ve seen many other kinds of adaptivity enabled with manufactured objects," said Changxi Zheng, an associate professor at Columbia University who co-directs Columbia’s Computer Graphics Group. “This work is a true breakthrough in being able to change the color of objects without repainting them.”

And for postdoc Parinya Punpongsanon (who co-authored the paper with Mueller), this could be one of the most economical ways to reduce waste when it comes to something as seemingly harmless as accessorizing.

“This is the first 3-D-printable photochromic system that has a complete printing and recoloring process that’s relatively easy for users,” Punpongsanon said. “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.”