Electrokinetic instability due to streamwise conductivity gradients in microchip electrophoresis

Dubey, Kaushlendra; Sanghi, Sanjeev; Gupta, Amit; Bahga, Supreet Singh

doi:10.1017/jfm.2021.672

Cited by 8 publications

(11 citation statements)

References 44 publications

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“…Similar to the previous studies of the bulk electrokinetic instability, [ 22–25 ] the bulk free charge ρ f in regions of conductivity gradients along the electric field is described by the conservation of the electromigration current and Gauss's law

ρ_{normalf} = - ε E \cdot \frac{\nabla σ}{σ} \sim \frac{\nabla c}{c}

where ε for the permittivity of water. By assuming the continuous or slow spatial variation of the anions and the reactive cations (Cu 2+ ), concentration gradient is mainly derived from the inert cations, such as the observed concentration valley of Rh +

\nabla c \sim \nabla c (inert) \sim \nabla c ({Rh}^{+})

Indeed, the observed concentration valley of inert cations is characterized by a sharp concentration gradient around R valley , generating the bulk free charge.…”

Section: Resultsmentioning

confidence: 75%

“…Similar to the previous studies of the bulk electrokinetic instability, [22][23][24][25] the bulk free charge ρ f in regions of conductivity gradients along the electric field is described by the conservation of the electromigration current and Gauss's law…”

Section: Correlation Between Concentration Valley and Recmentioning

confidence: 73%

“…The net charge under the non‐uniform electric field leads to the instability or an array of the vortices for REC. [ 22–25 ]…”

Section: Resultsmentioning

confidence: 99%

“…A quantitative and rigorous numerical simulation is desirable by resolving EDL deliberately

(λ_{D} \sim nm

and the bulk length scale approximately~mm), in order to address the vanishing of extended space charge, the formation of the concentration valley for inert cations and the consequent flow instability. ii)Since REC is correlated with the inert‐cation concentration valley in experiments, the bulk charge from the concentration gradient is proposed to be responsible for the observed flow. [ 22,23,25 ] The surface charges and the associated nonuniform electro‐osmotic flows along the walls might affect the vortices as well since the height of the microchannel is only around 30 μm. [ 25,30 ] By modifying PDMS surface from negative to positive charges through the surface treatment, REC is nearly unaffected experimentally.…”

Section: Resultsmentioning

confidence: 99%

“…[ 22,23,25 ] The surface charges and the associated nonuniform electro‐osmotic flows along the walls might affect the vortices as well since the height of the microchannel is only around 30 μm. [ 25,30 ] By modifying PDMS surface from negative to positive charges through the surface treatment, REC is nearly unaffected experimentally. But the interplay of free charge and surface charge together with the flow might be clearly resolved in numerical simulation. iii)Different from the previous study for the dendrite growth in the concentrated CuSO 4 with presented Na 2 SO 4 , [ 31,32 ] here we focus on the effect of the supporting electrolyte (Na 2 SO 4 ) on EOI at the moderate concentration of 1 m m CuSO 4 (Figure 5a), and find the suppression of EOI and emergence of REC once [ c (Na 2 SO 4 ) > c cri ].…”

Section: Resultsmentioning

confidence: 99%

See 4 more Smart Citations

Observation of Remote Electroconvection and Inert‐Cation Concentration Valley within Supporting Electrolytes in a Microfluidic‐Based Electrochemical Device

Huo

et al. 2022

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The electrochemical system is playing an increasingly important role in the advanced technology development for drinkable water and energy storage. While the binary electrolyte has been widely studied, such as the associated intriguing interfacial instabilities, multi‐component electrolyte is by far less known. Here, based on the classic Cu|CuSO4|Cu electrochemical system, the effect of supporting electrolyte is systematically investigated by highlighting the inert cations. In an annulus microfluidic device, the suppression of a previously known electro‐osmotic instability and the emergence of an array of the remote electroconvection along the azimuthal direction is found. A distinctive inert‐cation concentration valley propagates radially outward at a speed limited by the electromigration velocity. Remarkably, the simultaneous visualization of spatiotemporal evolution demonstrates the correlation of the concentration valley and electroconvection at a microscopic level. The underlying physical mechanism of their correlation is discussed, and the scaling analysis agrees with experiments. This work might inspire more future work on the multi‐component electrolyte, such as for the suppression of interfacial hydrodynamic instability and mitigation of dendrite growth, with the technological implications for water treatment and energy storage in batteries.

show abstract

ρ_{normalf} = - ε E \cdot \frac{\nabla σ}{σ} \sim \frac{\nabla c}{c}

\nabla c \sim \nabla c (inert) \sim \nabla c ({Rh}^{+})

Indeed, the observed concentration valley of inert cations is characterized by a sharp concentration gradient around R valley , generating the bulk free charge.…”

Section: Resultsmentioning

confidence: 75%

Section: Correlation Between Concentration Valley and Recmentioning

confidence: 73%

“…The net charge under the non‐uniform electric field leads to the instability or an array of the vortices for REC. [ 22–25 ]…”

Section: Resultsmentioning

confidence: 99%

“…A quantitative and rigorous numerical simulation is desirable by resolving EDL deliberately

(λ_{D} \sim nm

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 3 more Smart Citations

Observation of Remote Electroconvection and Inert‐Cation Concentration Valley within Supporting Electrolytes in a Microfluidic‐Based Electrochemical Device

Huo

et al. 2022

Small

View full text Add to dashboard Cite

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Decoupled second-order energy stable scheme for an electrohydrodynamic model with variable electrical conductivity

Zhu,

Pan,

Wang

et al. 2024

Journal of Computational and Applied Mathematics

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Electroosmotic Micromixing in Physicochemically Patterned Microchannels

Das,

Vanarse,

Bandyopadhyay

2024

Ind. Eng. Chem. Res.

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The study computationally explores the possibilities of vortex generation and micromixing inside a physicochemically patterned serpentine microchannel wherein a weak electrolyte is undergoing an electroosmotic flow. The results highlight the inefficiency of such serpentine microchannels in the absence of chemical patches due to the development of periodic electroosmotic and pressure-driven flows in the direction normal to the applied electric field. The periodic chemical patches with positive and negative ζ-potentials decorated on the microchannel walls facilitate reverse flow to enable the formation of an array of counter-rotating vortices inside the microchannel. While the rotational direction of the vortices could be periodically adjusted using an alternating field, the usage of channels with obtuse angles showed potential for uniform electroosmotic flow all along the serpentine channel. The number, size, and strength of vortices and mixing efficiency have been correlated with the number of chemical patches, ζpotential gradients, and the effects of filleted edges, among other parameters.

show abstract

Electrokinetic instability due to streamwise conductivity gradients in microchip electrophoresis

Abstract: Abstract

Cited by 8 publications

References 44 publications

Observation of Remote Electroconvection and Inert‐Cation Concentration Valley within Supporting Electrolytes in a Microfluidic‐Based Electrochemical Device

Observation of Remote Electroconvection and Inert‐Cation Concentration Valley within Supporting Electrolytes in a Microfluidic‐Based Electrochemical Device

Decoupled second-order energy stable scheme for an electrohydrodynamic model with variable electrical conductivity

Electroosmotic Micromixing in Physicochemically Patterned Microchannels

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