The present paper reports on the development of a biodegradable overmolded orthopedic implant: a metal bone fixing screw, which has been overmolded with a functionalized thin layer of biodegradable polymer to enhance cell adhesion during the healing process. The main challenges were to integrate precise, high-throughput and repeatable solutions to achieve a thin, defect-free structured polymer layer and to ensure a high and consistent implant quality. The work carried out entailed determining proper materials (Purasorb PDLG 5010) for the biodegradable overmolding layer and its economical substitute (NaKu PLA 100HF) to be used during initial tool and process development, designing the surface structure of the overmolded polymer layer, development of injection molding tools, as well as feeding and handling procedures. The injection overmolding process of Purasorb PDLG 5010 polymer was controlled, and the process parameters were optimized. In particular, the dominant process parameters for the overmolding, namely injection pressure, barrel temperature and mold temperature, were experimentally examined using a circumscribed three-factor central composite design and two quality marks; overmolding roughness and mass of polymer. The analysis of the experimental results shows that the mass of the overmolding is not feasible for use as the quality mark. However, the optimal parameters for the overmolding of a metallic implant screw with a thin, micro-structured polymer layer with a predefined roughness of the surface texture have been identified successfully.

For very accurate positioning of satellites μN-thrusters are required. These thrusters consist of ion emitters, which are typically made of W or Re. This study focuses on the investigation of needles (diameter 200–400 μm) and emitter-crowns manufactured by MIM. Realizing extremely high aspect ratios (up to 1:200) in combination with controlling of porosity and density gradient in the material is essential for this application and needs to address the following topics: advanced binder system, suitable starting powders, carefully adjusted injection molding parameters. After the development of the injection step, the sintering process and its influence on the densification behavior was studied. The above described application of a space propulsion system needs precise control of porosity and resulting capillary effects within the manufactured W and Re structures. Distinctive open porosity and density gradients were realised including denser cores and porous outer layers. The produced needles and crowns are currently tested for the use in ultra-precise formation flying space systems and terrestrial applications.