Most of the time, a material’s color stems from its chemical properties. Different atoms and molecules absorb different wavelengths of light; the remaining wavelengths are the “intrinsic colors” that we perceive when they are reflected back to our eyes.

So-called “structural color” works differently; it’s a property of physics, not chemistry. Microscopic patterns on some surfaces reflect light in such a way that different wavelengths collide and interfere with one another. For example, a peacock’s feathers are made of transparent protein fibers that have no intrinsic color themselves, yet we see shifting, iridescent blue, green and purple hues because of the nanoscale structures on their surfaces.

As we become more adept at manipulating structure at the smallest scales, however, these two types of color can combine in even more surprising ways. Penn Engineers have now developed a system of nanoscale semiconductor strips that uses structural color interactions to eliminate the strips’ intrinsic color entirely.