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For a project, I need to develop special array of reflectors.

Usually this is done through a process of plastic injection and vapor deposition, however the prototyping cost is very high.

Another solution I would like to explore is to 3d print the array of reflector with SLA printer like Form 3 and then deposit silver through the process of silver nitrate on solution.

However, I wonder if that could work and if the bond would be good enough, if the resin part would need prior treatment.

Another method could be by depositing a conductive layer and then do electroplating.

I'm not a chemist and don't really know where to start looking.

Thanks

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    $\begingroup$ Will a 3D-printed surface be smooth enough for your application? For your "array of reflectors" are you able to attach glass substrates? $\endgroup$
    – BalooRM
    Apr 30, 2020 at 19:53
  • $\begingroup$ Can you identify the specific resin that you will use? The chemistry of the resin may facilitate direct deposition of the mirror coating. $\endgroup$
    – BalooRM
    Apr 30, 2020 at 20:25
  • $\begingroup$ There are ways to smooth the surface by mechanical, or by over coating it. We don't need telescope grade optics though. $\endgroup$
    – Damien
    May 2, 2020 at 4:32
  • $\begingroup$ There are ways to bond silver to surfaces by chemical means without electroplating. I can describe possible approaches as an answer below. $\endgroup$
    – BalooRM
    May 2, 2020 at 13:26
  • $\begingroup$ Just an idea, but similarly to metal-loaded PLA filaments for Fused Deposition Modeling (FDM) 3-D printers (look at Filamet, by The Virtual Foundry), there may be some SLA resins working in a similar way (example). The principle is that you first print and then put your 3D printed model in an oven / kiln for sintering. The obtained surface can then be polished for a mirror-like aspect. The advantage is that you have a metallic surface at the end, which can thus be electro-plated with various reflective coatings... $\endgroup$
    – mranvick
    Mar 17, 2021 at 8:48

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My experience with glass reduced-silver mirrors is that bonding is poor, and that unprotected Ag rapidly degrades in air (a matter of days, in some cases). The bond to organic surfaces, I believe, might be worse.

If you have access to a fairly good vacuum pump (less than 10-4 Torr), it's not hard to aluminize. Watch a demo online.

You might also request a quote from an aluminization service, such as those in this list. In 2010, a 200 mm diameter mirror was said to cost about US$70 to aluminize. This British service has an online price list, starting at £20.

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  • $\begingroup$ I was looking into that, although seems to be fairly hard with a simple setup, and very low yield and is also time taking and difficult to scale. Panels are fairly large, at least 150x150mm but I will look more at commercials service. For oxidation of course it is known and need a protective coating atop. $\endgroup$
    – Damien
    May 2, 2020 at 4:36
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A traditional way of applying a silver coating to glass is through a chemical reaction using a reagent known as Tollens' Reagent. This reagent is prepared from silver nitrate as the source of silver.

Depending upon the surface chemistry of your cured SLA polymer, it may be possible to coat the polymer directly, as one would coat glass. There may also be a coating that will adhere to the SLA polymer and serve as a surface primer to which the silver from the Tollens' Reagent will adhere.

My recommendation would be first to identify the specific SLA resin that you will be using. This information should be available on the container, its packaging, or a Material Safety Data Sheet (MSDS).

Some research, such as an internet search, may provide additional information once the polymer chemistry is known. You might also find some helpful information from the SLA resin or printer manufacturer in the form of "Application Notes" that address applying surface coatings to SLA 3D-printed components.

I recommend performing a small-scale test to see what the Tollens' Reagent reaction does on the surface of a 3D-printed part that is made from the same resin that you will use. You might also experiment with different resins. Several resins may work equally well for forming your part while one provides a better surface for applying a mirror coating.

It will be necessary to apply a protective coating to the silvered surface, once prepared, to prevent oxidation.

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