] In their printing process, Epson uses two types of ink to
] produce circuit boards. The first is a conductive ink and
] the second is an insulator ink that is used to separate
] each layer from the next. This allows a printer to paint
] these inks in patterns on top of each other in an
] extraordinarily compact manner. In fact, the 20-layer
] board shown today looks only to be a a millimeter thick,
] if that.

I met a Brit at Foo camp who works for a Canon, researching this very thing. He discussed being able to "print" a fully working Cell phone that you buy online in the nezxt 15-20 years. Now, whether the end user will pay for basically a small factory when they are only "printing" the occasional purchase is up for debate, but its cool to see advances in this area.