Sustainable Synthesis of Copper Nanoparticles in 3D-Printed Microfluidic Devices: Effect of pH and Mixing Kinetics on Physicochemical Properties

Green synthesis of metal nanoparticles has attracted significant attention due to its sustainability, yet achieving precise control over their physicochemical properties via continuous-flow systems remains a challenge. This study evaluates the sustainable synthesis of copper nanoparticles using 3D-printed microfluidic reactors fabricated via the fused filament technique with glycol-modified polyethylene terephthalate. A systematic experimental design was performed to investigate the effects of the reducing agent concentration, the channel architecture, and the medium pH on particle size and morphology. Fluid dynamics theoretical modeling revealed a laminar flow regime, dominated by advection, where the serpentine geometry successfully induced stable homogeneous mixing. Statistical analysis identified pH as the most critical factor, demonstrating that an alkaline medium of pH 8 combined with a 5:1 reductant-to-precursor ratio optimizes the production of uniformly spherical copper nanoparticles with significantly smaller diameters. Advanced experiments also assessed the influence of flow rates and stabilizer agents on particle size, morphology and purity. These findings validate the integration of additive manufacturing and continuous microfluidics as a robust, low-cost, and eco-friendly platform for the reproducible and scalable production of metallic nanoparticles.