Recent advancement in induced-charge electrokinetic phenomena and their micro- and nano-fluidic applications

Feng, Huicheng; Chang, Honglong; Zhong, Xin; Wong, Teck Neng

doi:10.1016/j.cis.2020.102159

Cited by 26 publications

(17 citation statements)

References 148 publications

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“…This flow has thus far been mainly studied around the conducting surface of, for example, a metallic electrode or particle, either electrically activated or left floating [59][60][61][62][63][64][65][66][67]. It exhibits a quadratic dependence on the applied electric field and typically consists of a pair of counter-rotating vortices [68][69][70][71]. The first report of ICEO flow around a dielectric surface came from Thamida and Chang in 2002 [42].…”

Section: Iceo Flowmentioning

confidence: 99%

Review of nonlinear electrokinetic flows in insulator‐based dielectrophoresis: From induced charge to Joule heating effects

Xuan

2021

Electrophoresis

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Insulator‐based dielectrophoresis (iDEP) has been increasingly used for particle manipulation in various microfluidic applications. It exploits insulating structures to constrict and/or curve electric field lines to generate field gradients for particle dielectrophoresis. However, the presence of these insulators, especially those with sharp edges, causes two nonlinear electrokinetic flows, which, if sufficiently strong, may disturb the otherwise linear electrokinetic motion of particles and affect the iDEP performance. One is induced charge electroosmotic (ICEO) flow because of the polarization of the insulators, and the other is electrothermal flow because of the amplified Joule heating in the fluid around the insulators. Both flows vary nonlinearly with the applied electric field (either DC or AC) and exhibit in the form of fluid vortices, which have been utilized to promote some applications while being suppressed in others. The effectiveness of iDEP benefits from a comprehensive understanding of the nonlinear electrokinetic flows, which is complicated by the involvement of the entire iDEP device into electric polarization and thermal diffusion. This article is aimed to review the works on both the fundamentals and applications of ICEO and electrothermal flows in iDEP microdevices. A personal perspective of some future research directions in the field is also given.

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Section: Iceo Flowmentioning

confidence: 99%

Review of nonlinear electrokinetic flows in insulator‐based dielectrophoresis: From induced charge to Joule heating effects

Xuan

2021

Electrophoresis

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“…Yossifon and coworkers developed microfluidic diodes [61] as well as poly-electrolyte-based microfluidic ionic rectifiers [62]. In larger open channels (e. g. in micropipettes) the flow of ions is accompanied by electroosmotic flow and both ion current and electroosmotic transport can be rectified [10,63,64,65]. A hybrid system can be introduced (to suppress electroosmotic flow) by combining a microhole with ionomer materials.…”

Section: Microscale Ionic Rectifiers: a Materials Approachmentioning

confidence: 99%

Microscale Ionic Diodes: An Overview

et al. 2021

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Ionic rectifier membranes or devices generate uni-directional ion transport to convert an alternating current (AC) ion current input into stored energy or direct current (DC) in the form of ion/salt gradients. Electrochemical experiments 80 years ago were conducted on biological membrane rectifier systems, but today a plethora of artificial ionic rectifier types has been developed and electroanalytical tools are employed to explore mechanisms and performance. This overview focuses on microscale ionic rectifiers with a comparison to nano-and macroscale ionic rectifiers. The potential is surveyed for applications in electrochemical analysis, desalination, energy harvesting, electrochemical synthesis, and in selective ion extraction.

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“…If complete Debye screening takes place on the surface of the source and drain electrode terminals, almost all of the applied DC voltage will drop across the EDLs at the electrode/electrolyte interface, leaving no electric field in the bulk fluid any longer [47,56,84]. However, the appearance of an exchange current density from phase transfer of electrons may deteriorate the structure of EDLs formed on the electrode surface, and therefore permit electric field leakage outside of the EDL due to incomplete capacitive charging.…”

Section: Boundary and Conjugating Conditions For The Electric Fieldmentioning

confidence: 99%

“…Due to the unique rectification mechanism of the metal-dielectric Janus nanopore developed herein, it may be further extended for osmotic energy conversion application as well, in which an electrical current is produced by a horizontal salinity gradient even in the absence of external voltage excitation, as has been recently reported by the Yeh group using a Janus membrane [54,55]. Although some nanoscale ion diodes using induced-charge electroosmosis (ICEO) have been developed, it is rare to make use of the combined effect of ICEK and permanent interfacial polarization to construct an ionic circuit element, in which the missing of any one mechanism will disable the diode functionality [56]. It is firmly believed that ion current rectification driven by ICEK at the nanometer scale is going to inspire interdisciplinary research in soft matter, analytical chemistry, and osmotic energy harvesting in the near future.…”

Section: Introductionmentioning

confidence: 99%

A Simulation Analysis of Nanofluidic Ion Current Rectification Using a Metal-Dielectric Janus Nanopore Driven by Induced-Charge Electrokinetic Phenomena

et al. 2020

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We propose herein a unique mechanism of generating tunable surface charges in a metal-dielectric Janus nanopore for the development of nanofluidic ion diode, wherein an uncharged metallic nanochannel is in serial connection with a dielectric nanopore of fixed surface charge. In response to an external electric field supplied by two probes located on both sides of the asymmetric Janus nanopore, the metallic portion of the nanochannel is electrochemically polarized, so that a critical junction is formed between regions with an enriched concentration of positive and negative ions in the bulk electrolyte adjacent to the conducting wall. The combined action of the field-induced bipolar induced double layer and the native unipolar double layer full of cations within the negatively-charged dielectric nanopore leads to a voltage-controllable heterogenous volumetric charge distribution. The electrochemical transport of field-induced counterions along the nanopore length direction creates an internal zone of ion enrichment/depletion, and thereby enhancement/suppression of the resulting electric current inside the Janus nanopore for reverse working status of the nanofluidic ion diode. A mathematical model based upon continuum mechanics is established to study the feasibility of the Janus nanochannel in causing sufficient ion current rectification, and we find that only a good matching between pore diameter and Debye length is able to result in a reliable rectifying functionality for practical applications. This rectification effect is reminiscent of the typical bipolar membrane, but much more flexible on account of the nature of a voltage-based control due to induced-charge electrokinetic polarization of the conducting end, which may hold promise for osmotic energy conversion wherein an electric current appears due to a difference in salt concentration. Our theoretical demonstration of a composite metal-dielectric ion-selective medium provides useful guidelines for construction of flexible on-chip platforms utilizing induced-charge electrokinetic phenomena for a high degree of freedom ion current control.

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Recent advancement in induced-charge electrokinetic phenomena and their micro- and nano-fluidic applications

Cited by 26 publications

References 148 publications

Review of nonlinear electrokinetic flows in insulator‐based dielectrophoresis: From induced charge to Joule heating effects

Review of nonlinear electrokinetic flows in insulator‐based dielectrophoresis: From induced charge to Joule heating effects

Microscale Ionic Diodes: An Overview

A Simulation Analysis of Nanofluidic Ion Current Rectification Using a Metal-Dielectric Janus Nanopore Driven by Induced-Charge Electrokinetic Phenomena

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