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刘赵淼, 孙超, 逄燕, 王翔. 分岔结构处双乳液滴的动力学特性研究. 力学学报, 2024, 56(4): 1-9. DOI: 10.6052/0459-1879-23-605
引用本文: 刘赵淼, 孙超, 逄燕, 王翔. 分岔结构处双乳液滴的动力学特性研究. 力学学报, 2024, 56(4): 1-9. DOI: 10.6052/0459-1879-23-605
Liu Zhaomiao, Sun Chao, Pang Yan, Wang Xiang. Dynamic mechanism of double emulsion droplets flowing through the bifurcation structures. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(4): 1-9. DOI: 10.6052/0459-1879-23-605
Citation: Liu Zhaomiao, Sun Chao, Pang Yan, Wang Xiang. Dynamic mechanism of double emulsion droplets flowing through the bifurcation structures. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(4): 1-9. DOI: 10.6052/0459-1879-23-605

分岔结构处双乳液滴的动力学特性研究

DYNAMIC MECHANISM OF DOUBLE EMULSION DROPLETS FLOWING THROUGH THE BIFURCATION STRUCTURES

  • 摘要: 复合液滴在化工、医药和生物检测等领域有着广泛的应用, 尺寸以及壳层厚度是复合液滴应用过程中的关键特征参数, 研究复合液滴的动力学特性对建立相应的操控方法具有重要意义, 有助于进一步实现复合液滴的按需制备. 本文采用微流控技术制备了Y形和T形两种分岔结构, 研究了双重乳化液滴(简称双乳液滴)在分岔结构处的流动行为. 根据内、外液滴的分裂次数, 将流动模式划分为二次分裂、一次分裂和不分裂三种. 分析了流动模式的转变规律以及液滴长度对流动模式转变的影响, 通过内、外液滴延伸长度、颈部宽度和缝隙宽度等特征参数的演化过程, 将液滴运动过程划分为三个阶段, 不分裂模式下为挤压、过渡和恢复, 一次分裂以及二次分裂模式下为挤压、过渡和断裂, 并讨论了相应的动力学机制. 发现液滴长度的增加能有效降低液滴与通道之间的间隙宽度, 导致双乳液滴所受的挤压力与剪切力增加, 有利于液滴的分裂. 基于比较成熟的单乳液滴理论, 分别建立了内、外液滴的临界分裂条件, T形分岔结构的分裂临界线高于Y形, 并进一步构建了内、外液滴毛细数和初始长度决定的流动模式分布图, 可以很好地划分不同模式的分布区域, 对于调控双乳液滴特性参数具有重要参考价值.

     

    Abstract: Compound droplets have wide applications in various fields such as chemical engineering, medicine, and biological detection. The size and shell thickness are the key characteristic parameters in the application of compound droplets, and studying the dynamic characteristics of compound droplets is of great significance for establishing corresponding manipulation methods, which is helpful to further realize the on-demand production of compound droplets. In this study, Y-shaped and T-shaped bifurcation structures were prepared using microfluidic technology to investigate the flow behaviors of double emulsion droplets (referred to as double emulsion droplets) at the bifurcation structures. Based on the number of the inner and outer droplet breakups, the flow patterns were categorized into three types: twice breakup, once breakup, and non-breakup. The transition law of flow patterns and the influence of droplet length on the transition of flow patterns were analyzed. The evolution processes of characteristic parameters such as the inner and outer droplet extension length, neck width, and gap width were discussed to elucidate the corresponding dynamic characteristic, the droplet movement processes were divided into three stages: squeeze, transition and recovering in the non-breakup mode, and squeeze, transition and fracture in the once breakup and twice breakup modes. It was found that an increase in droplet length effectively reduces the gap width between the droplet and the channel, leading to increased squeezing and shearing forces on the double emulsion droplet, promoting droplet splitting. Based on well-established single emulsion droplet theories, critical splitting conditions for inner and outer droplets were separately formulated, the splitting critical line of T-shaped bifurcation structure was higher than that of the Y-shaped bifurcation structure. Furthermore, the capillary number and initial length of inner and outer droplets were identified to determine the distribution of flow patterns, and a flow pattern map was constructed, effectively delineating different pattern regions. It has important reference value for regulating the characteristic parameters of double emulsion droplets.

     

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