Optimal design of micromixer for preparation of nanoliposomes

•To address microscale laminar flow challenges, six micromixer designs are introduced.•Studying the effect of the circulating cavity on mixing index and pressure drop.•The influence of subchannel width ratio on mixing index and pressure drop is studied.•The optimized micromixer is effective at mixing for Re below 0.1 and above 20.•One-step preparation liposomes with average size of 39 nm and PDI of 0.104. Micromixers are essential components for controlling reactions in microfluidic devices, significantly enhancing their efficiency. This paper introduces an unbalanced separation and recombination micromixer with a circulating chamber and optimizes its geometric structure. The study investigates how the width ratio of the main subchannel and secondary subchannel, as well as the position of the circulating chamber, affect the mixing index and pressure drop at the micromixer's inlet and outlet. The enhanced mixing results from the unbalanced impact generated by the micromixer's separation and recombination, combined with the synergistic effect of fluid self-circulation. Simulation results indicate that the optimized micromixer achieves a mixing index close to 100 % when the Reynolds number exceeds 30, with a pressure drop of only 30 KPa at a Reynolds number of 50 in the micromixer's inlet and outlet. A microfluidic-based micromixer was fabricated using soft lithography and molding techniques. Liposomes were synthesized in a single step using soybean phospholipids, cholesterol, ethanol, and deionized water as raw materials. The micro-mixer exhibited exceptional mixing performance, enabling faster liposome synthesis compared to conventional methods. Additionally, the resulting liposomes exhibited smaller particle sizes and narrower size distributions. By adjusting the flow rates of the organic and water phases entering the micromixer, liposomes with a small particle size of 39 nm and a concentrated particle size distribution (PDI=0.104) were successfully produced. These findings highlight the microfluidic approach as a convenient, rapid, and efficient method for liposome preparation. Furthermore, the unbalanced separation and recombination micromixer with a circulating chamber demonstrated a simple structure, high mixing efficiency, and minimal pressure drop loss. It is versatile and suitable for various microreactor applications. [Display omitted]