Extrusion-based 3D printing of oral solid dosage forms: Material requirements and equipment dependencies

Extrusion-based 3D printing is steadily gaining importance as a manufacturing technique due to its flexibility and wide range of possible end-products. In the medical field, the technique is being exploited for a variety of applications and one of these is the production of personalised medicines. However, despite many proof-of-concept studies, more thorough insights in the production technique itself and the required material properties are needed before 3D printing can be fully exploited in a hospital or pharmacy setting. This research aims at clarifying the complex interplay between material properties, process parameters and printer-dependent variables. A variety of different polymers and polymer-drug blends were extruded (diameter 1.75 +/- 0.05 mm) and characterised in terms of mechanical, thermal and rheological properties. These properties, together with the processing temperature, printing speeds and different nozzle diameters of the 3D printer were linked to the quality of the end-product. Different failure mechanisms (mechanical, thermal) were assessed. Decisive material parameters (e. g. cross-over point) for optimal printing behaviour and the importance of printer construction (nozzle diameter) were clarified. In general, this study offers insight into the 3D printing process and will help to speed up future pharmaceutical formulation development for printlets.