Design Engineering

CSAIL project enables 3D printed objects to change color post-fabrication


Additive Manufacturing 3D printing MIT

Team developed a 3D printable ink that changes color when exposed to ultraviolet light. This allows them to recolor a multicolored object in just over 20 minutes.


Changing objects’ colors involves using ultraviolet light to activate some colors and visible light to deactivate others. Photo courtesy of the researchers.

3D printing has come a long way in the last several years. Yet one challenge still remains, once an object is printed, if it requires modification, it needs to be reprinted.

Researchers from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) are looking to solve this unique problem by looking at color changing properties. The team developed ColorFab, a method for repeatedly changing the colors of 3D printed objects, after fabrication.

The team developed a 3D printable ink that changes color when exposed to ultraviolet light. This allows them to recolor a multicolored object in just over 20 minutes. The project is focused on plastics and other common 3D printing materials but the researchers would like to adapt to fit a number of different applications and reduce the overall time it takes.

“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 order to develop the color-changing ability the team developed a simple hardware/software workflow. Using the ColorFab interface, users upload their 3D model, pick their desired color patterns, and then print their fully colored object.

Once an object is printed, the team uses ultraviolet light to activate desired colors and visible light to deactivate others. The team initially focused on using ultraviolet light to change the pixels on an object from transparent to colored, and a regular office projector to turn them from colored to transparent.

The ink is made of a base dye, a photoinitiator, and light-adaptable dyes. The light-adaptable dyes bring out the color in the base dye, and the photoinitiator lets the base dye harden during 3-D printing.

“Appearance adaptivity in general is always a superior feature to have, and we’ve seen many other kinds of adaptivity enabled with manufactured objects,” says Changxi Zheng, an associate professor at Columbia University who co-directs Columbia’s Computer Graphics Group.

The team tested ColorFab on three criteria: recoloring time, precision, and how quickly the color decayed.

A full recolouring process took upwards of 23 minutes and colors were a bit grainy, which they hope to improve on by activating colors closer together on an object.

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

Mueller co-authored the paper with postdoc Parinya Punpongsanon, undergraduate Xin Wen, and researcher David Kim. It has been accepted to the ACM CHI Conference on Human Factors in Computing Systems, which takes place in April in Montreal.


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