Not to long ago, @Jerrill_Johnson created a video showing how you can print a pcb board and use conductive paint as the traces.
Unfortunately, there isn’t an easy way to convert a PCB design to a printable board. There is a project called SolderSCAD that creates flashes but it doesn’t create the traces.
I created a new project called GerbPaintSCAD that will take a RS-274X extended Gerber Solder Stencil and convert it to an OpenSCAD file.
This is very preliminary and hasn’t been tested against anything other than very simple PCB’s designed for Single Sided in Fritzing. It requires the ability to run Ruby 1.9.2 from command line.
I don’t have a small enough nozzle to print these accurately so let me know how it goes. I included a bare bones arduino board if anyone wants to try it. I would love to know if anyone finds this useful.