The 3D printing of electronics has been making substantial progress over the last 12 months or so. We have witnessed several companies dive head on into the problem of getting printers to print electrical circuitry within polymer objects. One German company called Neotech AMT is a leader in the field. The have successfully released their electronics printing machine called the LBS 45XE, which uses light beam sintering technology to place conductive inks onto polymer substrates. More details on this method can be found here: http://3dprint.com/9931/3d-printed-electronics-neotech/

Check out a picture of a car made from a polymer material, which has electronics printed into it by Neoteck AMT: