Fauvel Matthieu, Trybala Anna, Tseluiko Dmitri, Starov Victor Mikhilovich, Bandulasena Himiyage Chaminda Hemaka
Department of Chemical Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, United Kingdom.
Department of Mathematics, Loughborough University, Loughborough, Leicestershire, LE11 3TU, United Kingdom.
Langmuir. 2022 May 24;38(20):6305-6321. doi: 10.1021/acs.langmuir.2c00026. Epub 2022 May 12.
Liquid foams are highly complex systems consisting of gas bubbles trapped within a solution of surfactant. Electroosmotic effects may be employed to induce fluid flows within the foam structure and impact its stability. The impact of external electric fields on the stability of a horizontally oriented monolayer of foam (2D foam) composed of anionic, cationic, non-ionic, and zwitterionic surfactants was investigated, probing the effects of changing the gas-liquid and solid-liquid interfaces. Time-lapse recordings were analyzed to investigate the evolution of foam over time subject to varying electric field strengths. Numerical simulations of electroosmotic flow of the same system were performed using the finite element method. Foam stability was affected by the presence of an external electric field in all cases and depended on the surfactant type, strength of the electric field, and the solid material used to construct the foam cell. For the myristyltrimethylammonium bromide (MTAB) foam in a glass cell, the time to collapse 50% of the foam was increased from ∼25 min under no electric field to ∼85 min under an electric field strength of 2000 V/m. In comparison, all other surfactants trialed exhibited faster foam collapse under external electric fields. Numerical simulations provided insight as to how different zeta potentials at the gas-liquid and solid-liquid interfaces affect fluid flow in different elements of the foam structure under external electric fields, leading to a more stable or unstable foam.
液体泡沫是高度复杂的体系，由捕获在表面活性剂溶液中的气泡组成。电渗效应可用于在泡沫结构内诱导流体流动并影响其稳定性。研究了外部电场对由阴离子、阳离子、非离子和两性离子表面活性剂组成的水平取向泡沫单层（二维泡沫）稳定性的影响，探究了改变气液和固液界面的影响。通过分析延时记录来研究在不同电场强度下泡沫随时间的演变。使用有限元方法对同一系统的电渗流进行了数值模拟。在所有情况下，外部电场的存在都会影响泡沫的稳定性，其稳定性取决于表面活性剂类型、电场强度以及用于构建泡沫单元的固体材料。对于玻璃单元中的十四烷基三甲基溴化铵（MTAB）泡沫，在无电场时泡沫坍塌50%的时间约为25分钟，在电场强度为2000 V/m时增加到约85分钟。相比之下，试验的所有其他表面活性剂在外部电场下泡沫坍塌更快。数值模拟揭示了气液和固液界面处不同的zeta电位如何在外部电场下影响泡沫结构不同部分的流体流动，从而导致泡沫更稳定或更不稳定。
