Researchers print structural colour with an inkjet printer | Hacker News Reader

Researchers print structural colour with an inkjet printer

physicsworld.com

77 pointszeristor16 comments

Sounds very interesting. Just started looking at the paper, which seems very complex to me "An alternative approach utilizes light absorption via localized surface plasmon resonances (LSPRs) of noble metal nanoparticles (NPs)".

I came across https://www.nano-resonance.com/ which appears to be the promotional page for the technique, it has a nice diagram which appears to show how the size of the silicon nanoparticle enhances certain wavelengths of light.

Very cool how they can use an inkjet printer for their approach.

Also see https://en.wikipedia.org/wiki/Lippmann_plate for a photographic process that creates colours using diffraction patterns.

https://www.youtube.com/watch?v=-DyrBDsKA5s is a fun video on lippmann plates.

Watched that video last night, really approachable and made me re-think everything I thought I knew about photography!

Yeah, it's very cool, I found a rather interesting document on the chemistry to create a lippmann plate 'The True Colour of Photography' by 'Hans I. Bjelkhagen, Darran P.M. Green' seems their exposure times where in the order of minutes.

I just watched that video the other day otherwise I'd have no idea what structural color is.

I always loved the holograms that were ever so popular in the 1980s. I just found some guy making lippmann plates on Etsy too:

https://www.etsy.com/listing/4343596905/white-flower-lippman...

Whoa...I worked on this exact thing around 20 years ago. But in my time, we were using laser pulses to ablate noble metals. Printer would have made life so much easier.

I don't understand these statements:

"...smart displays and vibrant art pieces (that won’t fade over time)... However, when the display is turned off, the images become visible, which allows for information display without using any energy."

Nowhere does it say that the coloration can be changed, once applied. The different-sized particles are embedded in acrylic. So how does this enable a "smart display?" I guess you can say that a turned-off monitor can now show "information," but that information printed on the screen would be static for all time... wouldn't it?

Presumably they're making the leap that this printing technology can be leveraged to develop an alternative display technology that would change the structure in real time, kind of like color e-ink displays.

It's quite the leap, but that's science communication for you!

IMOD’s (like Mirasol, which was abandoned) are pretty neat:

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

https://goodereader.com/blog/electronic-readers/the-rise-and...

Especially since the breakthrough was to encapsulate the colored bits to keep them from clumping.

See the image and caption at the top of the article

  Images printed with structural colour ink can be made both highly transparent to transmitted light (top) and at the same time reflect light from above in vivid colours (bottom) – two properties that are typically considered mutually exclusive

The printing on the phone is not visible when the phone display is on as the structural printing is highly transparent. When the display is off, the printing is visible because of the reflected light.

Yes, thanks; but that's neither a "smart" display nor a means to show anything but a single, static printout of "information" when the display is off.

Fascinating development. That means much, much greater control over ink deposition.

No doubt a potential worry for currency producers. Inkjets that have control over the physical build up of ink structure would pose an even greater threat of counterfeiting.

No doubt mints can introduce countermeasures to detect such threats but I'd suggest this tech (if perfected) will likely be too good for humans to detect a forgery at a glance. Reckon machine readers will become the order of the day, that's if physical paper/plastic currency continues to exist.

> Images printed with structural colour ink can be made both highly transparent to transmitted light (top) and at the same time reflect light from above in vivid colours (bottom)

Probably a foolish question, but wouldn't there be some unavoidable loss of brightness to the transmitted light, unless the structured color somehow "knows" to transmit light in one direction and reflect it in the other direction (which seems impossible given that it is printed by an inkjet)?

(Not an answer to your question, just a note that "top" and "bottom" refer to the illustration in the article -- the authors printed a printed a vivid color logo on what appears to be a smartphone screen. With the screen on, the image on the display shines through the design printed on top.

That might be a neat effect on the glass roof of a car.)

Structural colour works by destructive interference of reflected light. It requires the light to be scattered for this effect, so light travelling through at 90° won't be affected.

On the image in the article you can still see a trace of the image on the active screen from indirect light.

> The majority of printing processes today are performed using different > coloured pigments. However, there’s another type of colour called structural > colour, which typically uses nanoscale structures that interact with light > to produce a colour.

Doesn't the pigment act as ("natural") nanoscale structure as well?

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