Using their own 3D-printable ink that changes colour when exposed to UV light, the team can recolour a multi-coloured object in just over 20 minutes.
The project is focused on plastics but the researchers believe that people could eventually change the colour of their clothes or other items.
“Largely speaking, people are consuming a lot more now than twenty years ago, and they’re creating a lot of waste,” said MIT professor Stefanie Mueller, who co-wrote the new paper about the system. “By changing an object’s colour, you don’t have to create a whole new object every time.”
Mueller co-wrote the paper with postdoc Parinya Punpongsanon, undergraduate Xin Wen, and researcher David Kim. It was accepted to the ACM CHI Conference on Human Factors in Computing Systems, which takes place in April in Montreal.
According to CSAIL, previous colour-changing systems have been limited in their capabilities, such as single-colours and 2D designs.
To move beyond single-colour systems, the team developed a simple hardware/software workflow. First, using the ColorFab interface, users upload their 3D model, pick their desired colour patterns, and then print their fully coloured object.
Changing the multi-coloured objects involves using a projector model, which uses UV light to activate desired colours and visible light to deactivate others. Specifically, the team uses a UV light to change the pixels on an object from transparent to coloured, and an office projector to turn them from coloured to transparent.
Once a user has placed the object on the platform, they can select colours using the interface.
The team’s custom ink is made of a base dye, a photo-initiator, and light-adaptable dyes. The light-adaptable (photochromic) dyes bring out the colour in the base dye, and the photo-initiator lets the base dye harden during 3D printing.
The team tested ColorFab on three criteria: recolouring time, precision, and how quickly the colour decayed. A full recolouring process took 23 minutes, which could speed up by using a more powerful light or adding more light-adaptable dye to the ink.
The researchers also found the colours to be a bit grainy, which they hope to improve on by activating colours closer together on an object. For example, activating blue and red might show purple, while activating red and green would show yellow.
Mueller said that the goal is for people to be able to rapidly match their accessories to their outfits in an efficient, less wasteful way. Another idea is for retail stores to be able to customise products in real-time.
“This is the first 3D printable photochromic system that has a complete printing and recolouring process that’s relatively easy for users,” said 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.”