School of Mechanical Engineering, Yeungnam University , Gyeongsan 712-749, South Korea.
School of Chemical Engineering, Hanoi University of Science and Technology , 1st DaiCoViet, Hanoi, Vietnam.
Biomicrofluidics. 2015 Mar 24;9(2):024107. doi: 10.1063/1.4916228. eCollection 2015 Mar.
In this study, droplet formations in microfluidic double T-junctions (MFDTD) are investigated based on a two-dimensional numerical model with volume of fluid method. Parametric ranges for generating alternating droplet formation (ADF) are identified. A physical background responsible for the ADF is suggested by analyzing the dynamical stability of flow system. Since the phase discrepancy between dispersed flows is mainly caused by non-symmetrical breaking of merging droplet, merging regime becomes the alternating regime at appropriate conditions. In addition, the effects of channel geometries on droplet formation are studied in terms of relative channel width. The predicted results show that the ADF region is shifted toward lower capillary numbers when channel width ratio is less than unity. The alternating droplet size increases with the increase of channel width ratio. When this ratio reaches unity, alternating droplets can be formed at very high water fraction (wf = 0.8). The droplet formation in MFDTD depends significantly on the viscosity ratio, and the droplet size in ADF decreases with the increase of the viscosity ratio. The understanding of underlying physics of the ADF phenomenon is useful for many applications, including nanoparticle synthesis with different concentrations, hydrogel bead generation, and cell transplantation in biomedical therapy.
本研究基于二维数值模型和体积法研究了微流道双 T 型分叉（MFDTD）中的液滴形成。确定了产生交替液滴形成（ADF）的参数范围。通过分析流系统的动力学稳定性，提出了 ADF 的物理背景。由于分散流之间的相位差主要是由于合并液滴的非对称破裂引起的，因此在适当的条件下，合并状态变为交替状态。此外，还从相对通道宽度的角度研究了通道几何形状对液滴形成的影响。预测结果表明，当通道宽度比小于 1 时，ADF 区域向较低的毛细管数移动。随着通道宽度比的增加，交替液滴的尺寸增大。当该比值达到 1 时，可以在非常高的水分数（wf=0.8）下形成交替液滴。MFDTD 中的液滴形成显著取决于粘度比，ADF 中的液滴尺寸随粘度比的增加而减小。对 ADF 现象的潜在物理的理解对许多应用有用，包括具有不同浓度的纳米颗粒合成、水凝胶珠生成和生物医学治疗中的细胞移植。
