Arrangement and feedback effects of droplet swarms in a parallel microchannel device

Abstract

Droplet swarms are the dominant form of highly dispersed microdroplets in cavities. In the self-assembly of droplet swarms, the continuous phase tends to flow in the path of the minimum resistance, the arrangement of the droplet swarms tends to minimize the potential energy, and the two mechanisms compromise in competition. In this paper, whether droplet swarms can timely adjust the morphology is measured by the ratio of the average flow rate of the two-phase flow to that of the droplet swarms, so as to clarify the dominant mechanism of the arrangement of droplet swarms. The arrangement of droplet swarms dominated by different mechanisms and the distribution of that are introduced, and the prediction method for the arrangement of droplet swarms is proposed. The mechanism of the breakup of the microdroplet in the cavity is elucidated, and three modes of the breakup in the cavity are introduced. Furthermore, a resistance model for the microdevice is established to quantify the fluctuations of the pressure difference and the flow rate caused by the formation of droplet swarms. The influence of the feedback effects of droplet swarms on the uniformity of droplet formation and flow patterns is analyzed, indicating the ideal flow range for the formation of highly dispersed droplets in microchannels. This paper clarifies the arrangement and feedback effects of droplet swarms, which will guide the application of microdevices in reaction and mass transfer processes.