3D-Printed Passive Microfluidic Micromixer for Continuous and Tunable Liposome Synthesis

This study introduces a passive micromixer that integrates conventional microfabrication with cost-effective digital light processing (DLP) 3D printing for the controlled synthesis of liposomes with tunable physicochemical properties. The Lithography-Additive Integrated Microchannel (LAIM) consists of a Y-junction PDMS microchannel and an embedded 3D-printed twisted-triangle prism (TTP). A systematic numerical investigation was conducted to optimize the geometry of the mixing element by evaluating the effects of the center of rotation and pitch on mixing performance. The optimized configuration, TTP-C2 with a pitch of 1 mm, achieved mixing efficiencies exceeding 99% at Re = 1. Experimental validation using the optimized micromixer confirmed the enhanced mixing performance and its effectiveness for continuous liposome synthesis via an ethanol−water solvent exchange approach. Dynamic light scattering and zeta potential measurements demonstrated precise control over liposome size, dispersity, and stability, with particle sizes reduced to 85 ± 9 nm, low PDI values (∼0.10−0.20), and zeta potential reaching −30.3 ± 0.69 mV under optimized conditions. The effects of total flow rate, aqueous phase composition, and cholesterol-to-phosphatidylcholine ratio were systematically investigated, highlighting their critical roles in governing liposome formation.