Electrohydrodynamic Flow through a 1 mm² Cross-Section Pore Placed in an Ion-Exchange Membrane

Abstract

In recent years, the control of ionic currents has come to be recognized as one of the most important issues related to the efficient transport of single molecules and microparticles in aqueous solutions. However, the complicated liquid flows that are usually induced by applying electric potentials have made it difficult to address a number of unsolved problems in this area. In particular, the nonequilibrium phenomena that occur in electrically non-neutral fields must be more thoroughly understood. Herein, we report on the development of a theoretical model of liquid flows resulting from ion interactions while focusing on the so-called electrohydrodynamic (EHD) flow. We also discuss the development of an experimental system to optically and electrically observe EHD flows using a 1 mm 2 cross-section pore placed in an ion-exchange membrane where cation and anion flows can be separated without the use of a charged environment. Although micro/ nanosized flow channels are usually applied to induce electric double layer overlaps to utilize strong electroosmotic effects, our system does not require such laborious fabrication processes. Instead, we visualize EHD flows by using a millimeter size pore immersed in an alkaline aqueous solution. In this setup, liquid flows passing through the pore along the direction of ion flow, whose velocity reaches on the order of 1 mm/s, can be clearly observed by applying a few volts of electric potential. Furthermore, the transient phenomena associated with ionic responses are theoretically elucidated.

Development of glass micro-electrodes for local electric field, electrical conductivity, and pH measurements

“…Due to the concentration of the electric lines of force in a narrow channel, an almost uniform electric field is formed in the test section, which is suitable for the www.nature.com/scientificreports www.nature.com/scientificreports/ measurement of the electrical conductivity of electrolyte solutions. Using this method, it is expected that ion concentration fields as well as electric potentials at specific environments, such as interfaces at different size channel connections and near surfaces of ion-exchange membranes where enrichment and depletion occur under ionic current conditions [39][40][41] , are clarified. We will tackle such a challenging topic in the near future.…”

Characterisation of microparticle transport driven by ionic current conditions in electrically polarised aqueous solutions

“…The transport regime of microparticles is modified by the ion‐drag flow field. Here, we propose a novel method to generate the ion‐drag EHD flows [22, 23] in aqueous solution drastically decreasing the application voltage, where the external voltage does not exceed 2.0 V to avoid accelerating the electrolysis of water. We succeeded to dramatically reduce the applied voltage by preparing electrically polarised solutions.…”

Electrical Sensing of Au Nanoparticles Manipulated by an Optical Vortex

“…They theoretically and experimentally investigated induced-charge electroosmosis and induced-charge electrophoresis of asymmetric metallic particles exposed to DC and AC electric fields. In previous studies, we also discussed charge induction effects that drove electrohydrodynamic flows of liquids. , The present study provides experimental results that suggested some possibilities of ionic current and flow characteristics induced by Au NPs at the nanoscale, and further details will be clarified in the future.…”

“…In previous studies, we also discussed charge induction effects that drove electrohydrodynamic flows of liquids. 57,58 The present study provides experimental results that suggested some possibilities of ionic current and flow characteristics induced by Au NPs at the nanoscale, and further details will be clarified in the future.…”