Not a chemist so I hope you'll forgive any amateur mistakes. I found an overview of 3D printing resin photo-initiators here:


All these activate when subjected to light with a compatible wavelength.

Are there photo-initiator (blends) which require two different wavelengths to be present at the same time to activate?

If so, where can I find more information about them? If not, is there a specific reason something like this can't ever be created?

  • 3
    $\begingroup$ Usually if a molecule absorbs at, say, 400 nm it will also absorb at a shorter wavelength, but not the other way round. Usually it is easier to get visible light sources than UV i.e. 400-600 nm is easier/cheaper than 350 nm and below. (Also if you use light shorter than 300 nm ish there is a risk to your skin and cornea so great caution is needed, screening etc.) There seems no reason to make blends. $\endgroup$
    – porphyrin
    May 13 at 15:19
  • $\begingroup$ Thank you, that explains why there aren't such products. $\endgroup$
    – Stefan
    May 13 at 15:35
  • 1
    $\begingroup$ There are two-photon processes, requiring two separate: analyticalscience.wiley.com/do/10.1002/imaging.3042/full . This can, indeed, cause the material (photoactivatable GFP, in the citation), to accept differing energy photons. Another example is an IR viewing card, containing a phosphor activated by visible light, that then emits visible light when struck by IR photons: newport.com/f/near-infrared-nir-sensor-cards $\endgroup$ May 15 at 3:07


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