Key Takeaways

• Numerous color-changing coatings technologies and products exist.
• Walls that change color with the application of an electric field are available in the form of modules containing color-changing films available from E Ink.
• Can paints be far behind?

Recently I spoke with a long‑time architectural coatings industry veteran who asked whether it would ever be possible to design a paint whose color could change by remote control or some other external trigger. I told him that personally I wouldn’t want such a coating in my own living space, but he said he would love it and would use it frequently. I explained that while the idea isn’t impossible, the technology would likely emerge from another industry and would look very different from conventional paint.

Color‑changing coatings already exist, and in each case they rely on an external stimulus to drive the change:

• Thermochromic coatings: color varies with temperature. 
• Photochromic coatings: color changes in response to light. 
• Piezochromic coatings: color shifts under mechanical pressure or impact. 
• Electrochromic coatings: color changes when an electric current is applied.

How these coatings work-an example of a thermochromic coating

As one example, consider a thermochromic system based on leuco dyes. Leuco dyes can switch between a colorless and a colored form depending on changes in their molecular structure. In many systems, an acid acts as a developer; the acid protonates the leuco dye, altering its conjugation and producing color. A third component, typically a solvent, modulates this behavior. At higher temperatures the solvent is molten, disrupting protonation and allowing the dye to remain in its colorless form. At lower temperatures the solvent solidifies, enabling the developer to protonate the dye and shift it to its colored form. 

One of the most well‑known commercial uses of thermochromic technology appeared in 2007. Chromatic Technologies Inc. (CTI) pitched a thermochromic ink to Coors, which ultimately became the “blue mountains” on Coors Light cans, turning blue when the beer is cold enough to drink. CTI has since developed a range of chromatic technologies including photochromic inks and pressure‑activated inks, with applications across consumer packaged goods, healthcare, and industrial markets. (1)

Electrochromic coatings 

Electrochromic coatings, those that change color in response to an electric current, align most closely with what the industry veteran mentioned above envisioned.

In 2022, BMW introduced the iX Flow with E Ink technology, a vehicle with an exterior capable of exhibiting a range of grayscale colors from white to black when an electric field is applied. Many ePaper segments (each segment being an E Ink film) are applied to the body of the car to generate the coating; it is not applied as a liquid.  The coating consists of microcapsules containing negatively charged white pigments and positively charged black pigments. When an electric field  is applied, one pigment migrates to the capsule surface, producing the desired color in that microcapsule. Since that launch, BMW and E Ink have demonstrated that additional colors can be integrated into the exterior system.(2,3)

E Ink’s partner Seekink now offers color‑changing architectural wall modules using similar technology.(4) So yes, walls that change color exist today. The coatings just aren’t available in the form of a traditional liquid applied paint… at least not yet.

(1)  CTI – Why are the Coors Light Mountains Blue?

(2) Magical exterior colour-change: The BMW iX Flow featuring E Ink.

(3) What Is BMW's E-Ink Exterior, and Why Is It So Revolutionary?

(4)  E Ink Prism 3 Wall Display & Electronic Paper Wall - SEEKINK

#colorchangingcoatings #thermochromic #photochromic #piezochromic #electrochromic #eink #chromatictechnologies #CTI #innovation #coatings #chemicals #consulting

(photocredit:  alex azabache, pexels.com