Electrokinetic multiphase hydrodynamics

Electrokinetic phenomena around charged interfaces in electrolyte solutions represent a fundamental coupling between interfacial chemical physics and electro-mechanics. While the electrified solid–liquid interface has been extensively studied, its multiphase counterpart involving immiscible liquid–liquid interfaces presents unique challenges due to the interacting behaviors of ion transport within the Debye layer and solvent mixing layer. Electrokinetic multiphase hydrodynamics (EKmHD), dating back to the early 20th century, has regained prominence since the 2010s, supported by advanced methods spanning microfluidics, spectroscopy, molecular dynamics, phase-field-based modeling, coarse-grained analysis, and high-performance computing. After briefly sketching fundamental mechanisms, this review establishes a unified framework of experimental, theoretical, and numerical issues to consolidate the quantitative methodology of EKmHD, which is essential to uncover the underlying interfacial transport mechanisms. The systematic synthesis will not only advance predictive modeling methods for liquid–liquid electrokinetics but also propel the technological developments in multiphase-system-based energy conversion, bio-medical devices, and smart fluidics.