STOP PRESS: Now microelectronics can be 3D printed along with the usual plastic.
As you may be aware, microelectronics are made by a type of printing process, more specifically by etching areas defined by a photograph created on the surface to be etched.
Now microelectronics are being created by 3D printing, by using microelectronics in ink form. In addition, the printing is being combined with the printing of the usual plastic. This technology is just out of the gate at one of the research labs at Princeton University. Source
At this time one cannot expect the printed microelectronics to be as small as that made by semiconductor companies. This is because the 3D ink flows out of a nozzle, and it will be a long time before such nozzles can be made fine enough to create semiconductor geometries.
The microelectronics printed at Princeton comprised small LED dots, and they were printed as part of a 3D-printed contact lens.
Next time someone’s eyes are shining (like those of the Irish), be aware that the light may actually be generated electronically 
