SG16

The adhesive strength of inks to the substrate is measured with two tests: a tape test with 3M Scotch 234 and the conventional cross cut test. Usually, the change in electrical resistance is taken into account while performing these tests. For high frequency or radio applications, the surface roughness of the dry film is important.

Screen printing is a better choice for printing onto PCB surfaces. Copprint (an Israeli startup) has copper inks specificallý for FR4. Soldering is easier there...

https://www.youtube.com/watch?v=1up5a7z6tjE

Another option is this:

https://www.youtube.com/watch?v=OpObgG522sY

Yes you can do that.. a simpler way is to use screen printing directly on to a PCB

Check this out, might be interesting for you:

https://www.youtube.com/watch?v=OpObgG522sY

Yes stencil or screen printing is much faster for mass production. It is faster and you could directly print on a variety of substrates like FR4, plastic, glass and even paper. I'll wirte about that next

yes that's true, liquid inks usually have more resistance and this is a drawback. This is because the ink contains non-conducting materials which are required for the right viscosity and to prevent the silver to agglomerate. These can usually be removed by heating.

One can also use high intensity light to "weld" the silver particles together without damaging the plastic substrate. This requires an expensive setup but improves conductivity drastically... https://en.wikipedia.org/wiki/Photonic_curing