Jan 29, 2018 | By Benedict

A team of researchers at MIT's Computer Science and Artificial Intelligence Lab (CSAIL) has developed a new kind of 3D printable ink that makes it possible to recolor 3D printed objects after printing. The process has been named “ColorFab.”

When it comes to fashion and color, there are a number of rules and conventions you simply have to obey. “Blue and green should never be seen without another color in between,” for example, and that you can’t wear brown shoes with a black suit. For smaller things like earrings and smartphone cases, people also have their own ideas and rules about what colors match or clash.

But what if you could 3D print something like a smartphone case or a pair of earrings, and then change the color of those items at any point? CSAIL researchers have developed a 3D printable ink that makes that exact process possible, meaning you never need clash again. What’s more, they say it could one day be used to recolor something bigger and more significant—like a jacket or a pair of jeans.

The amazing process is called “ColorFab”, and it allows users to repeatedly change the color of a 3D printed object after printing. The trick is the use of ultraviolet light, which can be used to recolor a 3D printed object in just over 20 minutes. In future, it could be even faster.

MIT's Stefanie Mueller

(Image: Jason Dorfman)

While it sounds like a bit of a novelty, the MIT researchers—led by Stefanie Mueller, the X-Consortium Career Development Assistant Professor in the departments of Electrical Engineering and Computer Science and Mechanical Engineering—say the technique could actually benefit the environment.

“Largely speaking, people are consuming a lot more now than 20 years ago, and they’re creating a lot of waste,” Mueller says. “By changing an object’s color, you don’t have to create a whole new object every time.”

Interesting, but how does it work? Mueller and the team say their ColorFab process works with a simple hardware/software workflow: a user uploads a 3D model, picks their desired color patterns, and then prints the fully colored object. After printing, UV light can be used to activate desired colors while visible light can be used to deactivate others. The UV light changes pixels on an object from transparent to colored, while a regular office projector turns other pixels from colored to transparent.

It only works with the team’s specially developed custom ink, which is made of a base dye, a photoinitiator, and light-adaptable dyes. The light-adaptable (photochromic) dyes bring out the color in the base dye, while the photoinitiator lets the base dye harden during the 3D printing process.

One interesting challenge for the researchers was formatting each 3D model for 3D printing. Because only the outer shell of the model is printed with photochromic material (the inside is printed with a regular white material), the researchers had to determine which voxels lay on the outside and which on the inside before assigning materials. This ultimately required the team to assign a color to each voxel.

During testing, the researchers found that full recoloring took around 23 minutes, but that’s not the absolute limit: they say that, by using a more powerful light or adding more light-adaptable dye to the ink, the recoloring could be carried out in a shorter time. They also want to make the color less grainy, by activating colors closer together on an object.

The process sounds like a great deal of fun, but could it be genuinely useful? Mueller and the team think so, suggesting that the recoloring process could be deployed in retail stores in order to customize products in real time, letting a shopper quickly switch a shoe from brown to black, for example. This would allow retailers to keep fewer items in stock, saving them money while still giving customers a full range of color options.

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

The research has been documented in a paper, “ColorFab: Recoloring 3D Printed Objects using Photochromic Inks,” which can be read here.



Posted in 3D Printing Technology



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