3D-Mechatronic Integrated Devices (3D-MID) offer unique opportunities for combining and integrating electronic, optical, and mechanical functions on three-dimensional substrates to overcome the limitations of planar printed circuit boards. This paper presents an innovative fabrication process for integrating polymer optical waveguides onto 3D-MIDs to enable the transmission of optical signals in addition to electrical transmission. Using the Mosquito process, an optical waveguide core is wet-in-wet injected into the liquid cladding polymer. Therefore, a microdispensing needle is inserted into non-cured UV-cladding material, and a liquid core polymer is injected during relative motion. Finally, both materials are cured at once using UV radiation. Waveguides with different core diameters, single-to multimode, are possible to fabricate using this method. Concepts for optical connection of the waveguides to corresponding light sources and photodetectors are presented, enabling 3D-MID as electro-optical hybrid components. The entire process chain offers high flexibility and forms the basis for the fabrication and integration of polymer optical waveguides on three-dimensional components.