Two recent developments are getting us very close to printing electronics, one using inkjet printers to print conductive material for electronics and photonics and another, a conductive ink to create flexible electronics for books, displays and wearables.
The inkjet method of printing electronic material is developed by the National University of Singapore. The scientists there have developed a method that uses molybdenum disulfide with gold atoms to create a substance that can be layered in a flake like configuration and is able to be converted into a solution that has high viscosity that is able to be used with inkjet nozzles. The printing is built-up to create a flexible but strong substrate.
Conductive ink, another notable development, out of China, funded by the National Natural Science Foundation of China and developed by Rui Dang, Lingling Song, Wenjun Dong, Chaorong Li, Xiaobo Zhang, Ge Wang, and Xiaobo Chen, taking copper nanosheets to create a conductive ink that can be applied to a flexible sheet using a pen like utensil. The copper nanosheets are coated with silver nanoparticles to enable the copper nanosheets overlap (needed for contiguous conductivity). In the image shown, you can see that an LED was added to the sheet to prove that the ink is conductive and the idea works. The sheet was folded and crumpled to determine the robustness of this method and there was still an 80-90 percent reliability.
These technologies can help fabrication technologies, like 3D printers, to start developing objects with electronics embedded within them. Moreover, as development gets better and more precise, chemical processes to create PCBs can be reduced or eliminated.