The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
Langmuir. 2012 Jun 26;28(25):9250-8. doi: 10.1021/la301363d. Epub 2012 Jun 8.
Droplet emulsification in microfluidic devices involves the constant formation of fresh interfaces between two immiscible fluids. When the multiphase system contains surfactant, dynamic mass transfer of the surfactant onto the interface results in a dynamic interfacial tension different from the static interfacial tension measured in an equilibrium state. In this work, we have systematically investigated the effects of surfactant concentration and type on the dynamic interfacial tension of two different liquid-liquid two phase systems [N-hexane/water-sodium dodecyl sulfate (SDS) and N-hexane/water-cetyltrimethylammonium bromide (CTAB)] rapidly producing relatively small droplets in coaxial microfluidic devices. Dynamic interfacial tension experiments using the pendent drop method and a tensiometer were conducted, and a semiempirical equation was developed to put into context the effects of surfactants and the experimental conditions on droplet formation and dynamic interfacial tension in dynamic microchannel flows. The results presented in this work provide a more in-depth understanding of the dynamic effects of surfactants on droplet formation and the precise controllable preparation of monodispersed droplets in microfluidic devices.
在微流控设备中，液滴乳化涉及到两种不混溶流体之间不断形成新的界面。当多相系统中含有表面活性剂时，表面活性剂会在界面上发生动态质量转移，导致动态界面张力与平衡状态下测量的静态界面张力不同。在这项工作中，我们系统地研究了表面活性剂浓度和类型对两种不同的液-液两相体系（正己烷/水-十二烷基硫酸钠（SDS）和正己烷/水-十六烷基三甲基溴化铵（CTAB））的动态界面张力的影响，这些体系在同轴微流控设备中快速生成相对较小的液滴。使用悬滴法和张力计进行了动态界面张力实验，并开发了一个半经验方程，将表面活性剂和实验条件对液滴形成和动态微通道流中动态界面张力的影响置于上下文中。本工作的结果提供了对表面活性剂对液滴形成的动态影响的更深入理解，并能够精确控制微流控设备中制备单分散液滴。
