Home experiment of making a full circuit board with just 3D printing and a conductive ink pen.
Astounding!
http://www.youtube.com/watch?v=jCzmQLZKNA8&feature=youtu.be
no more soldering !!!
Would a conductive filament be easier than conductive ink?
@Keith_M I don’t have a dual extruder setup (yet) and I haven’t found a conductive filament that’s as conductive as this ink. I’ve been looking for someone to commercialize carbomorph. According to the paper on that conductive plastic formula it would be perfect for extruding circuit traces. But alas it remains vaporware. In the meantime, I’m on the lookout for some good conductive filament to do that experiment! 
@Jerrill_Johnson We should talk.
Wood filled filament contains 40% wood. What about PLA with high content of graphite or/ and silver powder?
alternative: a printhead which operates a ink filled syringe instead an extruder
Conductive filament can’t yet be used for carrying electrical signals. At 10000 ohms per cm, it’s mainly good for dissipating static, unless there is more conductive stuff out?
thats why I’m thinking about a high silver and/ or graphite content @Clint_O_Connor . Should be different from stuff with some fractions of graphite for ESD protection.
About a month after making that video the paint started to get lots of little cracks and the circuit broke, but it was quite promising. At work we have an air driven solder paste syringe that you run with a foot pedal switch. I thought that would be a great way to extrude the paint, but I need to figure out the cracking issue. My end goal is to see what cool thing people can print with with embedded 3D wiring patterns throughout an object… not just in two dimensions.
This is so cool.