The idea about "conductive ink has a minor drawback or two, One it will not stand a great deal of heat so don't try to solder the ink. and Two. the ink is limited in it's current handling capabilities. On a slightly off topic subject... When I first started designing PCB's I made a board that had to deliver a 10A 100 mS pulse to a coil... Being a careful engineer I made that track width' 300 mils as it was about 6" long by the time it went from the relay to the connector and I set a via with a 50 mil hole size figuring that when it went through the soldering process it would fill with solder and make a good solid connection... I made one real mistake, I had occasion to use the "Undo" feature in my PCB editor (Protel) and I inadvertently 'undid' the Via hole size "modification" I had previously done. I got my "first article" (sample board) and had the crew stuff it and to my complete chagrin... when I tested it the relay pulled in and nothing happened except a small puff of magic smoke (You can always tell when you let out the magic smoke... it smells terrible and the device quits working). I had undone the Modification to the Via and the plate through (on a 20 mil hole) simply wasn't up to the task of conducting 10A of current... It gave up the ghost and quit. The worst part was my employer was a control freak and he ordered the boards in parallel with my testing and without my knowledge. We had 100 boards made that had to have that hole drilled out and replaced the Via with a .1" piece of 18 ga solid copper wire. The lesson was Never send real current via a ... use a PTH hole of the right size and insure that it is soldered. Plated through small holes can be problematical as the plate through doesn't always work properly especially if the board house isn't top notch... Dirt and overused plating chemicals are responsible in equal parts are the offending conditions and are frequently found in "inexpensive" board houses. So If you are going to buy "Cheapo" PCB's realize that you have to do the job slightly differently... don't use Via's for higher current conductors... For the best success.
Doc