UV light system switches objects’ colours and patterns

The system, dubbed ‘ChromoUpdate,’ pairs an ultraviolet (UV) light projector with items coated in a light-activated dye. The projected light alters the reflective properties of the dye, creating colourful new images in just a few minutes.

According to the researchers, the technique could accelerate product development, enabling product designers to churn through prototypes without getting bogged down with painting or printing. “ChromoUpdate takes advantage of fast programming cycles – things that wouldn’t have been possible before,” said Michael Wessley, a postdoc at MIT’s Computer Science and Artificial Intelligence Laboratory.

The system builds on the researchers’ previous programmable matter system, called PhotoChromeleon. That method was “the first to show that we can have high-resolution, multicolour textures that we can just reprogram over and over again,” Wessely explained.

PhotoChromeleon used a lacquer-like ink comprising cyan, magenta, and yellow dyes. The user covered an object with a layer of ink, which could then be reprogrammed using light. First, they exposed the ink to a UV light from an LED, fully saturating the dyes. Then they selectively desaturated the dyes with a visible light projector, bringing each pixel to its desired colour, and leaving behind the final image.

Wessely said that although PhotoChromeleon was innovative; it was also sluggish – it took about 20 minutes to update an image. “We can speed up the process,” he added. And the researchers achieved that with ChromoUpdate, by fine-tuning the UV saturation process.

Rather than using an LED, which uniformly blasts the entire surface, ChromoUpdate uses a UV projector that can vary light levels across the surface. So, the operator has pixel-level control over saturation levels. “We can saturate the material locally in the exact pattern we want,” Wessely said.

According to the researchers, this helps saves time. For example, someone designing a car’s exterior might simply want to add racing stripes to an otherwise completed design, and ChromoUpdate lets them do just that, without erasing and re-projecting the entire exterior.

This selective saturation procedure allows designers to create a black-and-white preview of a design in seconds, or a full-colour prototype in minutes. That means they could try out dozens of designs in a single work session, a previously unattainable feat.

“You can actually have a physical prototype to see if your design really works,” said Wessely. “You can see how it looks when sunlight shines on it or when shadows are cast. It’s not enough just to do this on a computer.”

That speed also means designers could use ChromoUpdate for providing real-time notifications without relying on screens, they said. “One example is your coffee mug,” Wessely explained. “You put your mug in our projector system and program it to show your daily schedule. And it updates itself directly when a new meeting comes in for that day, or it shows you the weather forecast.”

Wessely hopes to keep improving the technology. At present, the light-activated ink is specialised for smooth, rigid surfaces like mugs, phone cases, or cars. But the researchers are working toward flexible, programmable textiles. “We’re looking at methods to dye fabrics and potentially use light-emitting fibres,” said Wessely. “So, we could have clothing – t-shirts and shoes and all that stuff – that can reprogram itself.”

The researchers have partnered with a group of textile makers in Paris to see how ChomoUpdate can be incorporated into the design process.