Unveiling Nonlinear Modes of Induced-Charge Electro-Osmosis in AC Electric Fields

Abstract

Induced-charge electro-osmosis (ICEO) is prevalent in electrochemistry and micro/nanofluidics, even when subjected to an alternating current (AC) electric field. Previous studies suggest that ICEO primarily occurs near electrodes or ion-selective membranes within a range of tens of microns. In this experimental study, we reveal the existence of additional modes in ICEO driven by an AC electric field. We demonstrate that nonlinear electroosmotic flow (EOF) can occur between two electrodes situated 5 mm apart through long-range electroconvection. Notably, we observe a soliton-like wave of ion concentration fluctuation traveling from the working electrode to the ground electrode, causing significant disruption to the electric triple layer (ETL) on the ground electrode. Consequently, both the ETL structure on the electrodes and the bulk fluid are profoundly influenced by an external electric field. These findings are vital for enhancing the understanding of intrinsic dynamics in electrochemical and energy systems and for the development of novel micro/nanofluidic devices.