Shen Feng, Li Yi, Liu Zhaomiao, Li XiuJun
College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing 100124, China.
Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968, USA.
Microfluid Nanofluidics. 2017 Apr;21(4). doi: 10.1007/s10404-017-1902-y. Epub 2017 Mar 27.
Droplet merging and splitting are important droplet manipulations in droplet-based microfluidics. However, the fundamental flow behaviors of droplets were not systematically studied. Hence, we designed two different microstructures to achieve droplet merging and splitting respectively, and quantitatively compared different flow dynamics in different microstructures for droplet merging and splitting via micro-particle image velocimetry (micro-PIV) experiments. Some flow phenomena of droplets different from previous studies were observed during merging and splitting using a high-speed microscope. It was also found the obtained instantaneous velocity vector fields of droplets have significant influence on the droplets merging and splitting. For droplet merging, the probability of droplets coalescence () in a microgroove is higher (50% < < 92%) than that in a T-junction microchannel (15% < < 50%), and the highest coalescence efficiency ( = 92%) comes at the two-phase flow ratio of 0.42 in the microgroove. Moreover, compared with a cylinder obstacle, Y-junction bifurcation can split droplets more effectively and the droplet flow during splitting is steadier. The results can provide better understanding of droplet behaviors and are useful for the design and applications of droplet-based microfluidics.
液滴的合并与分裂是基于液滴的微流控技术中重要的液滴操控方式。然而，此前尚未对液滴的基本流动行为进行系统研究。因此，我们设计了两种不同的微结构，分别用于实现液滴的合并与分裂，并通过微粒子图像测速技术（micro-PIV）实验，定量比较了不同微结构中液滴合并与分裂时的不同流动动力学特性。利用高速显微镜观察到了一些与以往研究不同的液滴合并与分裂过程中的流动现象。研究还发现，所获得的液滴瞬时速度矢量场对液滴的合并与分裂有显著影响。对于液滴合并，微槽中液滴聚并的概率（50% < < 92%）高于T型微通道（15% < < 50%），且在微槽中两相流率为0.42时聚并效率最高（ = 92%）。此外，与圆柱障碍物相比，Y型分支能更有效地分裂液滴，且分裂过程中的液滴流动更稳定。这些结果有助于更好地理解液滴行为，对基于液滴的微流控技术的设计与应用具有指导意义。
