The OptiK‑Net project, funded under the German initiative “Miniaturised optical systems with high integration density,” ran from 1 October 2019 to 31 March 2023. Its goal was to develop a complete technology chain for producing cost‑effective, highly integrated electro‑optical printed circuit boards (PCBs) that incorporate printed polymer optical waveguides. The consortium, led by Hotoprint Elektronik GmbH & Co. KG, included Leibniz University Hannover, ContiTech Elastomer‑Beschichtungen GmbH, Jänecke + Schneemann Druckfarben GmbH, Janoschka Deutschland GmbH, ficonTEC Service GmbH, Siemens AG (associate), Gallus Ferd. Ruesch AG (associate) and Continental Automotive GmbH (associate). The project produced two demonstrators: Demonstrator 1 integrates a waveguide passively onto the PCB surface, while Demonstrator 2 embeds the waveguide into a PCB interlayer, requiring full optical cladding and thermal resistance to withstand lamination processes.

Technically, the project focused on high‑throughput printing methods—flexographic, screen printing and deep‑drawing—to fabricate polymer waveguides on PMMA and polyimide (PI) substrates. Flexographic printing was used to create the core waveguide, exploiting the substrate and surrounding air as cladding. The core’s optical quality depends on contour accuracy, surface roughness and contamination. Flexographic printing of a 10‑layer waveguide (200 µm width, 50 µm height) achieved an average attenuation of 3.15 ± 0.3 dB cm⁻¹, a value that is competitive with conventional fiber and free‑space links while requiring fewer over‑pressure passes than analog flexographic structures. Screen printing was investigated for applying an upper cladding; a flat‑bed screen printer (Atma PA45) with 4 mm wide lines and 100 lines cm⁻¹ produced complete wetting of the core with only two layers, as confirmed by optical microscopy. Deep‑drawing was explored in collaboration with Janoschka Deutschland GmbH to increase material transfer per pass and improve industrial scalability.

Laser processing played a key role in shaping continuous waveguide geometries and creating alignment notches. A CO₂ laser cut the PMMA substrate to form a cavity for passive mounting in Demonstrator 1, ensuring that the waveguide could be positioned without exposing it to lamination temperatures. For Demonstrator 2, the waveguide was inserted into a PI interlayer; PI’s high temperature resistance allowed the waveguide to survive the lamination cycle. The project also examined the reduction of material build‑up at splitters and combiners by adjusting the ink formulation with Jänecke + Schneemann and refining the printing die with ContiTech.

Although organizational changes prevented full demonstrator runs during the project period, the procurement of a Challenger 650 press in Q3 2023 and the re‑investment of a Challenger 173 press for flexo and deep‑drawing enabled the consolidation of promising processes. The resulting technology chain allows direct printing onto finished PCBs, eliminating the need for lamination and thereby avoiding thermal and mechanical stress on the waveguides. The work culminated in several SPIE publications (e.g., Proc. SPIE 11815, 12007) and a DGaO processing report, documenting the industrial feasibility of printed optical waveguides for high‑speed Ethernet and other short‑range optical data links.