论文标题
4通道微流体流体动力陷阱，用于伸展流动中的液滴变形和合并
A 4-channel microfluidic hydrodynamic trap for droplet deformation and coalescence in extensional flows
论文作者
论文摘要
在这里，我们捕获并控制液滴的位置，仅使用没有外部场的流体动力来研究其动力学。流体动力陷阱通过合并按需系统以在同一微流体芯片上的T-Junction几何形状生成液滴，从先前实现的Stokes陷阱中进行调整。然后，我们通过施加毫秒压力脉冲将捕获的液滴施加了少量的液滴，从而对扰动进行了研究。停止压力脉冲后的液滴形状松弛遵循指数衰减。特征性的液滴形状松弛时间是从分散相变化的粘膜水滴的形状衰减曲线获得的，在连续相位带有轻质和重矿物油。选择系统以提供类似的平衡界面张力（5-10 mn/m），具有较大的粘度比。发现液滴形状松弛表明对液滴半径的依赖性很强，并且对分散与连续相粘度的比率的依赖性较弱。对于最高的粘度比，松弛时间较小，这可能表明，除了界面张力和液滴尺寸外，主要的粘度还可以控制液滴形状的松弛时间。在各种加工条件下进行短暂流动时，可以使用液滴形状的松弛时间告知乳液中液滴的响应。最后，提出了该平台直接在平面延伸流中直接可视化单个液滴合并的应用。因此，微流体四通道流体动力陷阱可用于研究微尺度上的液滴变形和液滴 - 滴滴相互作用的基本物理，以增强对单个液滴水平上乳液行为的了解。
Here, we trap and control the position of droplets to study their dynamics using hydrodynamic forces alone without an external field. The hydrodynamic trap is adapted from a previously implemented Stokes trap by incorporating a drop-on-demand system to generate droplets at a T-junction geometry on the same microfluidic chip. We then study confined droplet dynamics in response to perturbation by applying a millisecond-pressure pulse to deform trapped droplets. Droplet shape relaxation after cessation of the pressure pulse follows an exponential decay. The characteristic droplet shape relaxation time is obtained from the shape decay curves for aqueous glycerol droplets of varying viscosities in the dispersed phase with light and heavy mineral oils in the continuous phase. Systems were chosen to provide similar equilibrium interfacial tensions (5-10 mN/m) with wide variations of viscosity ratios. It is found that the droplet shape relaxation shows a strong dependence on droplet radius, and a weak dependence on the ratio of dispersed to continuous phase viscosity. The relaxation time is smaller for the highest viscosity ratios, potentially indicating that the dominant viscosity controls the droplet shape relaxation time in addition to the interfacial tension and droplet size. Droplet shape relaxation time can be used inform the response of droplets in an emulsion when subjected to transient flows in various processing conditions. Finally, an application of this platform for directly visualizing individual droplet coalescence in a planar extensional flow is presented. The microfluidic four-channel hydrodynamic trap can thus be applied for studying fundamental physics of droplet deformation and droplet-droplet interactions on the micro-scale to provide an enhanced understanding of emulsion behavior on an individual droplet level.
