Analysis of micromixing of non-Newtonian fluids driven by alternating current electrothermal flow

Kunti, Golak; Bhattacharya, Anandaroop

doi:10.1016/j.jnnfm.2017.06.010

Cited by 63 publications

(35 citation statements)

References 38 publications

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“…These limitations notwithstanding, local fluid recirculation can also be generated thermally via other means, for example, via the photoacoustic effect discussed previously in Section . Alternatively, local Joule heating as a consequence of the applied electric field, or externally imposed, for example using a laser, can give rise to temperature gradients in the fluid, that can also result in nonuniform permittivity ε and conductivity σ, and hence an accumulation of space charge ρ e that manifests as a time‐averaged (for AC fields) Maxwell body force

(⟨⟩, F_{e}) = \frac{1}{2} Re ([], \frac{σ ε}{σ + normali ω ε} \{\frac{1}{ε} (\frac{\partial ε}{\partial T}) - \frac{1}{σ} (\frac{\partial σ}{\partial T})\} (\nabla T \cdot E) E^{*} - \frac{1}{2} \frac{\partial ε}{\partial T} {|E|}^{2} \nabla T)

in a phenomena known as the electrothermal effect. In the above, σ is the conductivity of the fluid, T the temperature and E the electric field, the asterisk * denoting its complex conjugate and Re[·] the real part of the term in the parenthesis.…”

Section: Active Actuationmentioning

confidence: 99%

“…• AC electroosmotic flow -Capacitive charging [67][68][69][70] -Faradaic charging [68,71,72] Electrothermal effect [73][74][75][76][77][78][79][80][81][82] Interfacial electrokinetics…”

Section: Active Actuation Mechanismsmentioning

confidence: 99%

“…These limitations notwithstanding, local fluid recirculation can also be generated thermally via other means, for example, via the photoacoustic effect discussed previously in Section 3.2. Alternatively, local Joule heating as a consequence of the applied electric field, [73][74][75][76] or externally imposed, for example using a laser, [77][78][79] can give rise to temperature gradients in the fluid, that can also result in nonuniform permittivity ε and conductivity σ, and hence an accumulation of space charge ρ e that manifests as a time-averaged (for AC fields) Maxwell body force [226] 1 2…”

Section: Thermal Actuationmentioning

confidence: 99%

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On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

Ahmed

Ramesan

Lee

et al. 2019

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Microcentrifugation constitutes an important part of the microfluidic toolkit in a similar way that centrifugation is crucial to many macroscopic procedures, given that micromixing, sample preconcentration, particle separation, component fractionation, and cell agglomeration are essential operations in small scale processes. Yet, the dominance of capillary and viscous effects, which typically tend to retard flow, over inertial and gravitational forces, which are often useful for actuating flows and hence centrifugation, at microscopic scales makes it difficult to generate rotational flows at these dimensions, let alone with sufficient vorticity to support efficient mixing, separation, concentration, or aggregation. Herein, the various technologies—both passive and active—that have been developed to date for vortex generation in microfluidic devices are reviewed. Various advantages or limitations associated with each are outlined, in addition to highlighting the challenges that need to be overcome for their incorporation into integrated microfluidic devices.

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(⟨⟩, F_{e}) = \frac{1}{2} Re ([], \frac{σ ε}{σ + normali ω ε} \{\frac{1}{ε} (\frac{\partial ε}{\partial T}) - \frac{1}{σ} (\frac{\partial σ}{\partial T})\} (\nabla T \cdot E) E^{*} - \frac{1}{2} \frac{\partial ε}{\partial T} {|E|}^{2} \nabla T)

Section: Active Actuationmentioning

confidence: 99%

“…• AC electroosmotic flow -Capacitive charging [67][68][69][70] -Faradaic charging [68,71,72] Electrothermal effect [73][74][75][76][77][78][79][80][81][82] Interfacial electrokinetics…”

Section: Active Actuation Mechanismsmentioning

confidence: 99%

“…These limitations notwithstanding, local fluid recirculation can also be generated thermally via other means, for example, via the photoacoustic effect discussed previously in Section 3.2. Alternatively, local Joule heating as a consequence of the applied electric field, [73][74][75][76] or externally imposed, for example using a laser, [77][78][79] can give rise to temperature gradients in the fluid, that can also result in nonuniform permittivity ε and conductivity σ, and hence an accumulation of space charge ρ e that manifests as a time-averaged (for AC fields) Maxwell body force [226] 1 2…”

Section: Thermal Actuationmentioning

confidence: 99%

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On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

Ahmed

Ramesan

Lee

et al. 2019

Small

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“…Discrete electrodes embedded in microchannels indicate a potential opportunity for electrokinetic actuation either on the liquid medium or on granular samples suspended in the buffer solution [3]. Electrohydrodynamics (EHDs) has been acquiring unprecedentedly increasing attention from the microfluidic community since the last two decades [4][5][6]. Traditional DC electroosmosis (EO) [7,8], electrowetting on dielectrics [9], injection EHD [10], conduction EHD [11], traveling-wave induction EHD [12][13][14][15], inducedcharge electroosmosis (ICEO) [16][17][18][19][20][21][22][23][24], dielectrophoresis (DEP) [25][26][27][28][29][30], electrothermal (ET) induced flow [31][32][33][34][35][36][37], and electroconvective instability (EI) [38][39][40] near a permselective membrane are all authoritative methodologies where electric fields are employed to actuate liquid solutions in miniaturization systems.…”

Section: Introductionmentioning

confidence: 99%

“…Given its docile nature and ease of implementation with simple electrode structures, ET has been widely applied in microfluidics for various important applications, especially in cases that demand actuation of high-conductivity biological fluids. Kunti and co-researchers have recently conducted a series of theoretical investigations on ET actuation of the phase interface between immiscible binary flows [5,6,51]. In their great work, time-averaged ACET vortex flow motion in the bulk and nonlinear Maxwell electrical stress at the sharp material interface in externally-imposed AC/DC fields are combined delicately for propelling the insulating liquid phase in direct contact with electrolyte solution [52,53].…”

Section: Introductionmentioning

confidence: 99%

A microscopic physical description of electrothermal‐induced flow for control of ion current transport in microfluidics interfacing nanofluidics

et al. 2019

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The phenomenon of electrothermal (ET) convection has recently captured great attention for transporting fluidic samples in microchannels embedding simple electrode structures. In the classical model of ET‐induced flow, a conductivity gradient of buffer medium is supposed to arise from temperature‐dependent electrophoretic mobility of ionic species under uniform salt concentrations, so it may not work well in the presence of evident concentration perturbation within the background electrolyte. To solve this problem, we develop herein a microscopic physical description of ET streaming by fully coupling a set of Poisson‐Nernst‐Planck‐Navier‐Stokes equations and temperature‐dependent fluid physicochemical properties. A comparative study on a standard electrokinetic micropump exploiting asymmetric electrode arrays indicates that, our microscopic model always predicts a lower ET pump flow rate than the classical macroscopic model even with trivial temperature elevation in the liquid. Considering a continuity of total current density in liquids of inhomogeneous polarizability, a moderate degree of fluctuation in ion concentrations on top of the electrode array is enough to exert a significant influence on the induction of free ionic charges, rendering the enhanced numerical treatment much closer to realistic experimental measurement. Then, by placing a pair of thin‐film resistive heaters on the bottom of an anodic channel interfacing a cation‐exchange medium, we further provide a vivid demonstration of the enhanced model's feasibility in accurately resolving the combined Coulomb force due to the coexistence of an extended space charge layer and smeared interfacial polarizations in an externally‐imposed temperature gradient, while this is impossible with conventional linear approximation. This leads to a reliable method to achieve a flexible regulation on spatial‐temporal evolution of ion‐depletion layer by electroconvective mixing. These results provide useful insights into ET‐based flexible control of micro/nanoscale solid entities in modern micro‐total‐analytical systems.

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Pumping of Ionic Liquids by Liquid Metal‐Enabled Electrocapillary Flow under DC‐Biased AC Forcing

Xue

Liu

Jiang

et al. 2020

Adv Materials Inter

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A novel method is proposed to pump room‐temperature ionic liquids (ILs) by making use of liquid‐metal‐enabled electrocapillary flow driven by a DC‐biased AC forcing. The effectiveness of this pump strategy is demonstrated by both numerical simulation and experimental observation considering multiple frequency electrochemical polarization. The device can work practically in a wide range of different parameters, such as DC bias, AC voltage amplitude, the shape of the waveform, as well as the electrode separation. Though liquid metal (LM) has already been reported to help deliver the traditional sample of high‐conductivity aqueous electrolytes, its adaptability to drive ILs has apparent advantages, such as quicker pump flow rate due to greater initial interfacial ion adsorption, and much longer operating life due to its nonvolatile feature. The results prove invaluable for the elaborate construction of flexible electrokinetic platforms taking high‐speed ILs as the working fluid.

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Analysis of micromixing of non-Newtonian fluids driven by alternating current electrothermal flow

Cited by 63 publications

References 38 publications

On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

A microscopic physical description of electrothermal‐induced flow for control of ion current transport in microfluidics interfacing nanofluidics

Pumping of Ionic Liquids by Liquid Metal‐Enabled Electrocapillary Flow under DC‐Biased AC Forcing

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