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Comment by johnyzee | Hacker News Reader

> The secret behind the vivid blue coloration of our tarantula lies not in the presence of blue pigments, but rather in the unique structure of their hair, which incorporates nanostructures that manipulate light to create this striking blue appearance

Cool!

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It’s actually surprisingly common. For instance, butterflies and peacocks also use this: https://en.wikipedia.org/wiki/Structural_coloration

(In fact, I’m pretty sure I read somewhere that only a handful of blue pigments exist in nature; the vast majority of blue animals and plants use structural colouration instead. Can’t recall where I saw it, though.)

If I'm not mistaken, thin-film anodization one more example of this:

https://en.wikipedia.org/wiki/Anodizing

- "Anodic films can also be used for several cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add reflected light wave interference effects. [...] The colour [sic] formed is dependent on the thickness of the oxide (which is determined by the anodizing voltage); it is caused by the interference of light reflecting off the oxide surface with light travelling through it and reflecting off the underlying metal surface."

There's one more example in metallurgy I don't remember the name of: where you can get metals to spontaneously form color gradients by heating them in a specific way. Like, there's a thermal gradient, and that somehow translates to an oxidation-thickness gradient, which makes a rainbow. (?)

There is work currently being done to turn this idea into a usable paint : https://www.science.org/doi/10.1126/sciadv.adf7207

Something can be both common and amazing ?

I find the blue sky one of these common yet amazingly beautiful phenomena.

No one said otherwise. One can add context without invalidating the statement they responded to.

Ok then, fair enough.

Reminds me of when Lexus also used nanostructures to create their "structural blue"

https://newsroom.lexus.eu/natures-brillance-captured---new-l...

Structural color is really amazing. Same thing on the wings of Christmas beetles that gives them a blue green oil slick look.

I'm waiting for a paint company to come out with this for house painting. 1 coat for life.

that's what Iridigm displays use (acquired by Qualcomm in 2004):

https://www.qualcomm.com/news/releases/2004/09/qualcomm-acqu...

And now apparently owned by... Apple!

https://appleinsider.com/articles/15/12/15/apple-has-taken-o...

what is the difference between that and what pigment does?

If you ground a structural color material down into a dust, it would no longer produce the same color effects anymore. By contrast, pigments and dyes have their absorption at the molecular level and would only lose their effect if you modified their chemical bonds.

With structural color, the substances themselves do not have this spectral absorption characteristic. Instead, very specific configurations are needed to produce different effects. Imagine microscopic arrays of prisms and mirrors.

Also, structural colorization is often very angle-dependent. The iridescence of flowers, feathers, etc. comes from this characteristic. At different angles of incidence of light reflecting to an observer, different colors become visible. Pigments do not do this.

Also, I think there may be differences in usage of these terms between physicists, chemists, and biologists. While writing this, I also realize I am not sure if the terms become ambiguous for relativelt inert, microscopic crystals. From a physics standpoint, I think the crystals may exhibit structural color and pigment effects. From a practical standpoint, they might behave a little more like a pigment in that you could have what seems a fine dust and mix it into paint. But, if you dissolved it to separate the crystals back into free molecules, it would then only exhibit the pigment effects.

Apparently, structural color is also a lot more vivid (in the paint example, it reflects back almost 100% of the light, vs. 50% for pigment).

If it reflects back 100% of the incident light, it wouldn't have a blue appearance, would it?

I believe it changes the wavelength of the reflected light, producing the observed color.

From what I understand, with structural colors the structure is causing certain wavelengths to preferentially reflect or transmit, or behaves as a diffraction grating to split the white light. What you're describing sounds like fluorescence.

The difference between two lamps, one red the other blue, making one purple light and purple paint.

The design or setup makes one purple the other is purple.

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