Gemstones like precious opal are beautiful to look at and deceivingly complex. As you look at such gems from different angles, you will see a variety of tints glisten, causing you to question what colour the rock actually is. It is iridescent thanks to something called structural colour – microscopic structures that reflect light to produce radiant hues.
Customisable fabrication
Structural colour can be found across different organisms in nature, such as on the tails of peacocks and the wings of certain butterflies. Scientists and artists have been working to replicate this quality, but outside of the lab, it is still very hard to recreate, causing a barrier to on-demand, customisable fabrication. Instead, companies and individual designers alike have resorted to adding existing colour-changing objects like feathers and gems to things like personal items, clothes, and artwork.
Now MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) researchers have replicated nature’s brilliance with a new optical system called 'MorphoChrome'.
MorphoChrome allows users to design and program iridescence onto everyday objects (like a glove, for example), augmenting them with the structurally coloured multicolour glimmer reminiscent of many gemstones.
You select particular colours from a colour wheel in the team’s software program and use their handheld device to 'paint' with multicolour light onto holographic film. Then, you apply that painted sheet to 3D-printed objects or flexible substrates such as fashion items, sporting goods, and other personal accessories, using their unique epoxy resin transfer process.
MorphoChrome’s programmable color process adds a luminous touch to things like a necklace charm of a butterfly. What started as a static, black accessory became a shiny pendant. Image: Courtesy of the researchers.
“We wanted to tap into the innate intelligence of nature,” says MIT Department of Electrical Engineering and Computer Science (EECS) PhD student and CSAIL researcher Paris Myers SM ’25, who is a lead author on a recent paper presenting MorphoChrome. “In the past, you couldn’t easily synthesise structural colour yourself, but using pigments or dyes gave you full creative expression. With our system, you have full creative agency over this new material space, predictably programming iridescent designs in real time.”
MorphoChrome showed it could add a luminous touch to things like a necklace charm of a butterfly. What started as a static, black accessory became a shiny pendant with green, orange, and blue glimmers, thanks to the system’s programmable colour process. MorphoChrome also turned golfing gloves into beginner-friendly training equipment that shine green when you hold a golf club at the correct angle, and even helped one user adorn their fingernails with a gemstone-like look.
Holographic photopolymer film
These multicolour displays are the result of a handheld fabrication process where MorphoChrome acts as a 'brush' to paint with red-green-blue (RGB) laser light, while a holographic photopolymer film (used for things like passports and debit cards) is the canvas. Users first connect the system’s handheld device to a computer via a USB-C port, then open the software program. They can then click 'send colour' to rapidly transmit different hues from their laptop or home computer to the MorphoChrome hardware tool.
This handheld device transforms the colours on a screen into a controllable, multicolour RGB laser light output that instantly exposes the film, a sort of canvas where users can explore different combinations of hues.
About the size of a glue bottle, MorphoChrome’s optical machine houses red, green, and blue lasers, which are activated at various intensities depending on the colour chosen. These lights are reflected off mirrors toward an optical prism, where the colours mix and are promptly released as a single combined beam of light.
After designing the film, one can fabricate diverse structurally coloured objects by first coating a chosen object with a thin layer of epoxy resin. Next, the holographic film (litiholographics) – composed of a photopolymer layer and a protective plastic backing – is bonded to the object through a 20-second ultraviolet cure, essentially using a handheld UV light to transfer the coloured design onto the surface. Finally, users peel off the film’s protective plastic sheet, revealing a colour-changing, structurally coloured object that looks like a jewel.
Do try this at home
MorphoChrome is surprisingly user-friendly, consisting of a straightforward fabrication blueprint and an easy-to-use device that encourages do-it-yourself designers and other makers to explore iridescent designs at home.
Instead of spending time searching for hard-to-find artistic materials or chemically synthesising structural colour in the lab, users can focus on expressing various ideas and experimenting with programming different radiant colour mixes.
The array of possible colours stems from intriguing fusions. Nagenta, for instance, is created after the system’s blue and red lasers mix. Selecting cyan on the MorphoChrome software’s colour wheel will mix the green and blue lights.
Users should note that the time it takes to fully expose the film to each colour will vary, based on the researchers’ multicolour findings and the intrinsic properties of holographic photopolymer film. MorphoChrome activates green in 2.5 seconds, whereas red takes about three seconds, and blue needs roughly six seconds to saturate. The reason for this discrepancy is that each colour is a particular wavelength of light, requiring a certain level of light exposure (blue needing more than green or red).
Look at this hologram
MorphoChrome builds upon previous work on stretchable structural colour by co-author Benjamin Miller PhD ’24, Professor Mathias Kolle, and Kolle’s Laboratory for Biologically Inspired Photonic Engineering group at MIT's Department of Mechanical Engineering. The CSAIL researchers, who work in the Human-Computer Interaction Engineering Group, say that MorphoChrome also advances their ongoing work on merging computation with unique materials to create dynamic, programmable colour interfaces.
Going forward, their goal is to push the capabilities of holographic structural colour as a reprogrammable design and manufacturing space, empowering individuals and industries alike to customise iridescent and diffuse multicolour interfaces. “The polymer sheet we went with here is holographic, which has potential beyond what we’re showing here,” says co-author Yunyi Zhu ’20, MEng ’21, who is an MIT EECS PhD student and CSAIL researcher. “We’re working on adapting our process for creating entire 3D light fields in one film.”
Customising full light-field holographic messages onto objects would allow users to encode information and 3D images. One could imagine, for example, that a passport could have a sticker that beams out a 3D green check mark. This hologram would signal its authenticity when viewed through a particular device or at a certain angle.
The team is also inspired by how animals use structural colour as an adaptive communication channel and camouflage technique. Going forward, they are curious how programmable structural colour could be integrated into different types of environments, perhaps as camouflage for soft robotic structures to blend into an environment. For instance, they imagine a robot studying jungle terrain may need to match the appearance of nearby bushes to collect data, with a human reprogramming the machine’s colour from afar.
In the meantime, MorphoChrome recreates the majestic structural colour found in various ecosystems, connecting a natural phenomenon with our creative processes. MIT researchers will look to improve the system’s colour gamut and maximise how luminous mixed colours are. They are also considering using another material for the device’s casing, since its current 3D-printing housing leaks out some light.
“Being able to easily create and manipulate structural colour is a great new tool, and opens up new avenues for discovery and expression,” says Liti Holographics CEO Paul Christie SM ’97, who was not involved in the research.
“Simplifying the process to be more easily accessible allows for new applications to be developed in a wider range of areas, from art and jewellery to functional fabric.”