"In the last decades, the field of printed electronics has emerged and in the last years it also expanded from two dimensions into three dimensions. The production of 3D structures with conductive features has gained much focus, in particular for the emerging field of internet of things (IoT), where 3D objects are all interconnected.
The main challenge of printing conductive structures onto 3D objects is the deposition of liquids onto substrates that are uneven or sometimes have very complex topography. As the material can only be deposited when the substrate faces the nozzle and only one material can be printed at the time, the conventional printing method represents a time-limiting process often resulting in an uneven spreading of the ink and, as a consequence, in non-reproducible devices. Other methods to create conductive features that have been applied include transfer printing, like stamping."