Mass-Transfer-Controlled Dynamic Interfacial Tension in Microfluidic Emulsification Processes

详细信息    查看全文

• 作者：Kai Wang ; Liming Zhang ; Wanlu Zhang ; Guangsheng Luo
• 刊名：Langmuir
• 出版年：2016
• 出版时间：April 5, 2016
• 年：2016
• 卷：32
• 期：13
• 页码：3174-3185
• 全文大小：717K
• ISSN：1520-5827

文摘

Varied interfacial tension caused by the unsaturated adsorption of surfactants on dripping droplet surfaces is experimentally studied. The mass transfer and adsorption of surfactants, as well as the generation of fresh interfaces, are considered the main factors dominating the surfactant adsorption ratio on droplet surfaces. The diffusion and convective mass transfer of the surfactants are first distinguished by comparing the adsorption depth and the mass flux boundary layer thickness. A characterized mass transfer time is then calculated by introducing an effective diffusion coefficient. A time ratio is furthermore defined by dividing the droplet generation time by the characteristic mass transfer time, t/t_m, in order to compare the rates of surfactant mass transfer and droplet generation. Different control mechanisms for different surfactants are analyzed based on the range of t/t_m, and a criterion time ratio using a simplified characteristic mass transfer time, t_m*, is finally proposed for predicting the appearance of dynamic interfacial tension.