High-Throughput Microfluidic Synthesis of Biocompatible Carbon-Dot-Loaded Liposomes: Geometry-Dependent Encapsulation and CFD Analysis of Mixing

Microfluidic platforms offer precise control over nanocarrier synthesis but remain underexploited for low-cost production of multifunctional carbon dot–liposome (CDLiposome) systems. Here, we optimize the synthesis of CD-loaded liposomes using four PMMA micromixer geometries─Serpentine, SARS, Circular Features (CF), and Chambers─and quantitatively link encapsulation performance, mixing physics, and computational fluid dynamics (CFD) models. All devices produced monodisperse vesicles with hydrodynamic diameters of ∼150–200 nm. Encapsulation experiments combining two total flow rates (TFR = 75 and 150 mL/h) and three flow rate ratios (FRR = 1:1, 1:2, and 2:1) revealed that FRR is the dominant parameter: a lipid-to-aqueous FRR of 2:1 yielded significantly higher encapsulation efficiencies across all geometries, whereas TFR had no statistically significant effect, enabling high-throughput operation at 150 mL/h. The Chambers device exhibited the best performance, achieving encapsulation efficiencies approaching 90%, followed by CF, SARS, and Serpentine. To rationalize these trends, we compared experimental mixing profiles with COMSOL Multiphysics simulations using Mixture and Euler–Euler frameworks and multiple RANS closures. At low TFR (2 mL/h), the Laminar model accurately reproduced PIV-validated velocity fields, whereas at higher TFRs (75–150 mL/h), an empirically tuned Custom 2 model was required to match the scalar mixing efficiency, demonstrating that no single RANS closure can simultaneously capture both momentum and scalar transport across regimes. Finally, MTT assays in Vero cells showed cell viabilities of ≥70% up to 400 μg/mL after 24 and 48 h, confirming high in vitro biocompatibility of the optimized CDLiposomes.