Study on Co-flow Effect on Janus Droplet Generation Based on Step Emulsification

Abstract

Abstract Continuous phase co-flow can increase the throughput and control the flexibility of step emulsification, and has an important effect on droplet microfluidic. In this study, a multi-channel step emulsification device was developed to generate Janus droplets and to study the effects of both continuous phase co-flow and dispersed phase flow on the generation of Janus droplets. Janus droplets were successfully prepared by the device, and the generation stability was optimized by using glass capillaries instead of microcapillary film based on their different wall contact angles at the channel outlet. The results showed that when the continuous phase co-flow rate increased, the resulted Janus droplet diameter decreased, and the generation frequency increased. When the flow rate of dispersed phase increased, both the diameter and generation frequency of the generated Janus droplets increased. Within the scope of this study, the diameter and the generation frequency of the Janus droplets could be controlled to be 638–1640 μm and 0.02–2.2 Hz, respectively. In addition, three-component droplets were generated successfully and steadily by a chip which was prepared based on the two-component droplet generation device. By changing the flow rates of two phases, the droplet diameter and frequency could also been tuned on-line. It was found that the co-flow effect had a greater impact on the generation of three-component droplets because of the result that the three-component droplet diameter changed greater than the two-component Janus droplet when changing both the continuous and dispersed phase flows. The results of this study provided a basis and method for micro and trace research of chemical and analysis industry.