The inks have great compatibility with a wide variety of materials! The main thing you need to look out for is choosing a substrate which can withstand the curing temperature of the ink (210C for rigid, 140C for flex).
For plastic substrates, a good indicator of their temperature tolerance is the glass transition temperature - the glass transition is actually a range, but the Tg is a good estimate for where you’ll start to see structural problems with the substrate.
Some examples of substrates we’ve seen done:
- Polyimide (kapton)
- Carbon fibre
- Paper (coated is better, uncoated needs multiple prints)
- Acrylic (see note below)
- FR4/FR1, of course
- Rogers RF substrates (see note on surface energy below)
We’ve printed on acrylic with the flexible conductor, the main thing to look out for with acrylic is that untreated acrylic will deform laterally when heated, which may cause things like mounting holes to be misaligned after curing. Heat-treated acrylic performs much better.
The other far less important thing you may want to look out for is the surface energy of the substrate. Lower surface energy materials like PTFE (teflon) will lead to poorer adhesion. That said, I have printed on teflon before, as well as substrates which include PTFE, so it depends on whether strong adhesion is important in your target application.