High-Throughput Production of Droplets Using Mini Hydrodynamic Focusing Devices with Recirculation

In this study, a mini hydrodynamic focusing device with two feedback channels was designed to produce droplets of two immiscible liquids with a high throughput. Compared to conventional hydrodynamic focusing devices, the design can prevent the two liquids from forming parallel flows that suppress the dispersed phase from breaking up into droplets with high throughputs. A red aqueous solution and fully hydrogenated kerosene with 0.3 wt % Span 80 surfactant were used as the dispersed phase and continuous phase, respectively. Experiments confirmed that the feedback channels can enhance the interface instability and consequently facilitate the production of droplets. Moreover, an arrangement where the dispersed phase is on both sides of the continuous phase was found to remarkably improve the production of droplets because of the increased interface. The mini hydrodynamic focusing device is suitable for solvent extraction and other chemical processes that require a high surface/volume ratio.