The plan is to print a complete and fully assembled device, instead of creating a case and then laboriously filling it with electronic circuit boards and other components. The trick is to print layer upon layer of conducting and semiconducting polymers in such a way that the circuitry the device requires is built up as part of the bodywork.
Three-dimensional printers are already valuable tools for making prototypes of newly designed products. They deposit layers made from droplets of smart polymers, which gradually build up into 3D shapes. Such printing techniques are sophisticated enough to print working prototypes with mechanical parts that move as they would in the final product. The Berkeley researchers allow the electronics to be included in the printed device, rather than being added later at greater cost.