Wang K, Lu Y C, Xu J H, Luo G S
The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, People's Republic of China.
Langmuir. 2009 Feb 17;25(4):2153-8. doi: 10.1021/la803049s.
Interfacial tension is an important physical property affecting the droplet formation process in microfluidic devices. This work presents the variation of dynamic interfacial tension caused by slow adsorption of surfactant, as well as its influence on the liquid/liquid microdispersion process in a T-shaped microchannel. Using hexane/water-Tween 20 as the working system, it was observed that the droplet size changed with the variation of surfactant concentration when the concentration of Tween 20 was lower than 10 mmol/L, but hardly changed at higher concentrations, which was caused by the unsaturated adsorption and saturated adsorption of surfactant, respectively. The saturated interfacial tension was measured with an interfacial tension meter, and the relationship between the interfacial tension and the droplet diameter was established. Accordingly, the dynamic interfacial tension with unsaturated adsorption of surfactant was determined. The main factors affecting the dynamic interfacial tension were discussed, and a semiempirical equation was established to characterize those effects.
界面张力是影响微流控器件中液滴形成过程的重要物理性质。本文研究了表面活性剂缓慢吸附引起的动态界面张力变化，以及其对T形微通道中液/液微分散过程的影响。以正己烷/水-吐温20为工作体系，观察到当吐温20浓度低于10 mmol/L时，液滴尺寸随表面活性剂浓度变化而改变，而在较高浓度时几乎不变，分别是由表面活性剂的不饱和吸附和饱和吸附引起的。用界面张力仪测量了饱和界面张力，并建立了界面张力与液滴直径之间的关系。据此，确定了表面活性剂不饱和吸附时的动态界面张力。讨论了影响动态界面张力的主要因素，并建立了一个半经验方程来表征这些影响。
