Hu Qingming, Jiang Tianyi, Jiang Hongyuan
School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China.
School of Mechatronics Engineering, Qiqihar University, Wenhua Street 42, Qiqihar 161006, China.
Micromachines (Basel). 2020 Feb 5;11(2):169. doi: 10.3390/mi11020169.
A two-phase flow axisymmetric numerical model was proposed to understand liquid metal droplet formation in a co-flowing capillary microfluidics device based on a phase field model. The droplet detachment processes were observed in the experiment and are in good agreement with the simulation method. The effects of the viscosities and flowrates of the continuous phase fluid, interfacial tension as well as the wetting property of the metallic needle against the bulk liquid metal on the droplet formation and production rate were numerically investigated. It was found that the droplet diameter decreased with the increment of the viscosities and flowrates of the outer phase carrier fluid. The dispersed phase fluid with high interfacial tension tended to prolong the time for equilibrium between the viscous drag force and interfacial tension on the liquid-liquid fluid surface, delaying the droplet to be pinched off from the capillary orifice and causing large droplet diameter. Finally, the wetting performance of the metallic needle against the liquid metal was explored. The result indicate that the droplet diameter became less dependent on the contact angle while the size distribution of the liquid metal droplet was affected by their wetting performance. A more hydrophilic wetting performance were expected to prepare liquid metal droplet with more monodispersity. The numerical model and simulation results provide the feasibility of predicting the droplet formation with a high surface tension in a glass capillary microfluidic device.
基于相场模型，提出了一种两相流轴对称数值模型，以了解共流毛细管微流控装置中液态金属微滴的形成过程。在实验中观察到了液滴的脱离过程，并且与模拟方法吻合良好。数值研究了连续相流体的粘度和流速、界面张力以及金属针相对于液态金属本体的润湿性对液滴形成和产生速率的影响。研究发现，液滴直径随着外相载液的粘度和流速的增加而减小。具有高界面张力的分散相流体倾向于延长液 - 液流体表面上粘性阻力与界面张力之间达到平衡的时间，延迟液滴从毛细管孔口被夹断，并导致液滴直径增大。最后，探讨了金属针相对于液态金属 的润湿性能。结果表明，液滴直径对接触角的依赖性变小，而液态金属微滴的尺寸分布受其润湿性能的影响。预期更亲水的润湿性能能够制备出单分散性更好的液态金属微滴。该数值模型和模拟结果为预测玻璃毛细管微流控装置中具有高表面张力的液滴形成提供了可行性。
