Manufacturing a rainbow whose colors never fade

Once again science gets poetic, and colorful. Scientists at the University of Buffalo have found a way to manufacture a structured rainbow that never fades.

The bright iridescent colors on a butterfly's wing never fade. The gold and silver beetles, which have carapaces that shine and reflect like the were sitting on the bumper of a car in the sixties and got chromed along with it, also don't ever look less dapper. And the new little hand-held rainbow that researchers at the University of Buffalo have made won't ever fade either. They're all examples of structural color.

Most colors we see in life are the result of pigments. White light shines on them, they absorb most of it, and send back out only a few wavelengths which we see as a definite color. Over time, pigments can be washed out, worn away, or bleached, and the color simply fades. This isn't a problem for structural colors. Instead of pigments absorbing lights and emitting light, layers of neutral-colored material forms a kind of grating. This grating reflects light in such a way that it interferes with itself, peaks getting closer to each other, and creates different wavelengths, all coming out of the same structure. Insects like the gold and silver beetle pull this trick by putting down chitin in ever-thinning layers, causing light that bounces off one layer to not quite be able to sync up with the light that bounces off one layer above, and so on. The University of Buffalo scientists are keeping mum on how they made this particular rainbow.

They do say they've found a relatively cheap and easy to manufacture it. This could mean that the little rainbow will show up on devices that filter color - like machines that analyse the color in medical samples to check for disease - and in devices that show color, like cell phones. In the meantime, we get to look at a little glowing rainbow that won't fade away unless we tear it to pieces.

Top Image: University of Buffalo

Via Wiley Online Library.