Electric fields enable tunable surfactant transport to microscale fluid interfaces

Abstract

The transport dynamics of oil-soluble surfactants to oil-water interfaces are quantified using a custom-built electrified capillary microtensiometer platform. Dynamic interfacial tension measurements reveal that surfactant transport is enhanced under a D.C. electric field, due to electromigration of charge carriers in the oil toward the interface. Notably, this enhancement can be precisely tuned by altering the field strength and temporal scheduling. For the first time, we demonstrate electric fields as a new parameter to manipulate surfactant transport to microscale fluid-fluid interfaces.

Phase-Dependent Surfactant Transport on the Microscale: Interfacial Tension and Droplet Coalescence

“…(d) Measured dynamic IFT showing that the IFT decays faster when the electric field is stronger. Reprinted figures with permission from ref . Copyright 2019 American Physical Society.…”

“…The dynamic IFT can then be extracted using eq with measured Δ P and R c , both as a function of time. Following the work by Alvarez et al, Sengupta et al , utilized this microtensiometer apparatus to further investigate the effect of electric fields on the surfactant transport to oil–water interfaces using a setup similar to that shown in Figure (c), in which the electric field is applied across the electrodes on the side of the cell. The dynamic IFT is measured with two different surfactants, in which they found that the transport of oil-phase surfactants is enhanced due to the electrophoresis of charge carriers (Figure (d)).…”

Effects of Surfactant Solubility on the Hydrodynamics of a Viscous Drop in a DC Electric Field

“…In the literature many experimental works [55,[81][82][83] show that the transport of bulk surfactant is nonlinearly coupled with drop curvature, surfactant physicochemical properties, and external flows. Analytical investigation on drop hydrodynamics with surfactant sorption kinetics is challenging due to the complex nonlinear coupling between surfactant diffusion, sorption kinetics, drop deformation and Maragoni stress.…”

“…Table I summarizes the existing theoretical and numerical investigations in the literature. In most of these studies [42][43][44][45][46][47][48][49][50][51]55], surfactants are assumed to be insoluble and the surface tension is described using either a linear relationship, or more realistically the Langmuir equation of state…”

“…and have profound effects on the drop shape and dynamics [60][61][62][63][64][65]. Electric field can in turn affect the rate of sorption kinetics [55]. These results naturally lead to the following inquiries: What effects does adsorption and/or desorption have on EHD and how do they affect the interplay between all the various stresses?…”