[jlas]

Neat, but seems like a novelty.

As far as usage in teaching circuits, it wouldn't be very useful after the first class. The bulk of learning about circuits is math.

[jmpe]

That's because it is a novelty. You're pretty much restricted to planar circuits with this approach and the resistance is pretty bad.

[DonGateley]

Not at all. You can paint over a crossover with something (Whiteout I think) and then just write across it. When you can do that it's far more flexible than multi-layer with via's.

The resistance will not be an issue either for signal traces. Only those receiving or delivering power such as Vcc or the output of an audio amp or cable drivers.

I'm looking to enhance it with software for another KS project WaterColorBot, a very low cost plotter. With that, multi-line overlapping traces can be created to lower resistance and it could even automatically implement their suggestion of rubbing over a dried trace with something hard to compress the colloidal silver in it into making better contact between particles.

[sitkack]

Yeah, smells like edutainment. How is a breadboard a bad thing? It costs 1/3 what this pen costs and can be reused to make circuits that carry real current and signals, not just electronic holiday cards.