(2ix) A Microfluidic Chip Structure with Ultra-High Liquid-Liquid Mass Transfer Performance

Enhancing the mass transfer rate of the droplet formation stage can further increase the upper limit of mass transfer performance of microfluidic systems. In this study, an asymmetric step-T-junction was developed to enhance mass transfer by modifying the structure of the droplet formation position. Furthermore, a novel experimental method was established to differentiate the mass transfer contributions of the droplet formation stage and the motion stage. The mass transfer contribution of the droplet formation stage can range from 38.1% to 48.2% for the asymmetric step-T-junction. Moreover, the mass transfer coefficient of the droplet formation stage can be 27.8-64.3 times higher than that of the droplet motion stage. Additionally, a reliable explanation for the observed decrease in the volumetric mass transfer coefficient with an increase in residence time was provided. Under the same residence time, the mass transfer coefficient of the asymmetric step-T-junction is more than an order of magnitude higher than that of the conventional T-junction.