Hybrid manufacturing, which integrates three-dimensional printing and injection molding, presents a scalable solution for producing personalized oral dosage forms. This study presents a systematic comparison between overprinting and overmolding, two hybrid manufacturing strategies, to assess their influence on tablet microstructure, drug release dynamics, and processing performance. Using a Taguchi L9 experimental design, formulations containing polycaprolactone, poly(vinylpyrrolidone-co-vinyl acetate), and theophylline (5-30% w/w) were processed via hot-melt extrusion and fabricated into bilayer tablets using either overprinting or overmolding. Characterization techniques such as infrared spectroscopy, differential scanning calorimetry, powder X-ray diffraction, oscillatory rheology, scanning electron microscopy, and micro-computed tomography revealed that overprinted tablets retained the porous structure of the printed layer, which facilitated faster drug release governed by Fickian diffusion. Overmolded tablets exhibited structural compaction due to molten polymer infiltration, reducing porosity and shifting release towards anomalous, diffusion-relaxation-controlled mechanisms. Drug release was primarily influenced by design parameters in overprinted tablets, whereas drug loading dominated performance in overmolded systems. The optimal filament formulation was identified at 15% drug loading, balancing molecular dispersion and mechanical stability. Kinetic modelling using the Korsmeyer-Peppas equation confirmed distinct release mechanisms between the two approaches. Additional structural modifications, such as solid barrier layers, modulated surface integrity and defect formation under prolonged exposure. These findings position overprinting as a platform for personalized, design-driven drug release, while overmolding offers robustness and controlled, sustained delivery. Together, these hybrid techniques provide complementary tools for advancing individualized pharmaceutical manufacturing.

Compatibilizers that enhance sustainability and improve the miscibility of polymer blend components have garnered significant attention. This study investigates the difference between the synthetic chain extender Joncryl^® ADR 4468 and the natural epoxidized linseed oil (ELO) Merginat 8510100 as compatibilizers for thermoplastic starch/poly (butylene succinate) (TPS/PBS) blends. Blends containing 40% TPS and 60% PBS were prepared with 1, 3, and 5 phr of each compatibilizer, along with a reference with no additives. The properties of these blends were evaluated using tensile testing, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheology, and scanning electron microscopy (SEM). The findings indicate that while Joncryl^® ADR 4468 significantly improved tensile strength, it also resulted in a brittle fracture. In contrast, ELO batches exhibited greater ductility, albeit with lower tensile strength. These differences are attributed to the chain extension and minor cross-linking effects of Joncryl^® ADR 4468, compared to the increased chain mobility arising from ELO’s plasticizing and compatibilizing actions. Supporting evidence for these observations includes increased cold crystallization temperature (T_cc) and melting temperature (T_m), greater storage modulus along with higher complex viscosity, strengthened interfacial adhesion, and fewer morphological defects in Joncryl^® ADR 4468 blends. These results highlight the importance of selecting an appropriate compatibilizer based on specific application requirements. Overall, this study addresses the knowledge gap regarding the loadings of Joncryl^® ADR 4468 and ELO in TPS/PBS blends and provides a basis for further optimization strategies, such as the incorporation of binary compatibilizers, alternative grafting-based compatibilizers, and twin-screw blending modifications.