Structural color - mimicking the brilliance of nature

The brilliant-blue feathers of a kingfisher, iridescent hues of butterfly wings, and metallic shimmering chitin covers of beetles – these examples of natural beauty are based on structural color. Mimicking them is both a desire and a huge challenge for chemical manufacturers, as the structures are complex. Dr. Rupa Darji, a BASF research manager, along with her team, collaborated with academics from Harvard University to fundamentally understand structural color and how it can enable further application in an industrial setting. Rupa has been an industrial scientist for more than 15 years.

Why are structural colors interesting for BASF?

There are several reasons why structural color is so interesting. As scientists, we are always looking for new ways to improve the stability of traditional colorants that can degrade and fade over time. In contrast, inorganic-based structural color will not fade. Additionally, they offer great opportunities to create new appealing optical effects that have not been created before with traditional colorants. For example, both angle-independent and angle-dependent colors are difficult to make with traditional pigments. Angle-independent means that the color does not change at any observation angle. With angle-dependent colors, in contrast, the appearance changes depending on observation angle – which is an appealing feature for cosmetics.

How did Harvard get involved in the project?

At BASF, we have a lot of expertise in chemistry and engineering. Since structural color really depends on light and how it reflects from its structures, we needed some help to better understand the physics. Fortunately, I found a professor at Harvard’s engineering school who understands the fundamentals and physics of structural color. His lab offered to create a digital model that could predict what kinds of colors can be made based on the structural features of materials. Basically, the collaboration involved Harvard creating these models while we did the experimental work at BASF. We worked in parallel – learning together was key. As a result, jointly exploring this new area of structural color research was a rewarding experience.

How did the project change the work on structural color for BASF?

There are many applications where structural color could be used. They provide value for multiple businesses. Thanks to the collaboration with Harvard, we now have a model that can predict the color based on formulation and design. This saves BASF time and effort when we design materials for an application. It also helps our businesses utilize structural color in their formulations and products. Due to its versatility, structural color can be used in many ways, especially to ensure long-lasting colors for applications ranging from coatings to cosmetics.

What’s your favorite color?

I used to have a favorite color, but now I look at colors differently. Today, I have an appreciation for many colors, because each one is special and difficult to make. When traveling with family and friends, I’ve learned how other countries and cultures have uniquely applied color in their daily lives, which has opened my perspective. So, working in this research area has changed my appreciation for both color and nature.