Electrolyte dependence of particle motion near an electrode during ac polarization

Wirth, Christopher L.; Sides, Paul J.; Prieve, Dennis C.

doi:10.1103/physreve.87.032302

Cited by 26 publications

(36 citation statements)

References 33 publications

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“…Sides and co-workers have used total internal reflection microscopy to study the nanometer-scale oscillations in particle height, and have established that while electrophoresis is the predominant force causing oscillatory motion, there are hydrodynamic interactions that cause the particle oscillations to be nonsymmetric in time and out of phase with the electric field [30]. They further established that the phase angle between the applied field and the particle height was correlated with particle separation or aggregation, and that the time-average height varied with electrolyte type, frequency, and field strength [13,23,26,27]. More recently, Dutcher et al used confocal microscopy to demonstrate that the average particle height is correlated with both the magnitude of the lateral flow as well as the effective particle diffusivity and consequent propensity to form disordered or hexatic aggregates [28].…”

Section: Introductionmentioning

confidence: 99%

“…A variety of additional phenomena, including electrophoresis [3], dielectrophoresis [4,5], induced dipolar interactions [6,7], electro-osmotic flow [2], electrohydrodynamic (EHD) flow [8][9][10], and induced charge electro-osmosis (ICEO) [11][12][13], are known to significantly alter the particle behavior and give rise to new particle configurations. In particular, colloids have been widely observed to form planar aggregates near an electrode surface in response to an oscillatory electric field applied normal to the electrode [7][8][9][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Although there is broad agreement that electrically induced fluid flow pushes the particles to aggregate laterally, the relative contribution of different types of proposed flows-including EHD [10,21], Faradaically coupled electro-osmotic flow (FCEO) [22], and ICEO [22,26]-remains unclear.…”

Section: Introductionmentioning

confidence: 99%

“…First, particles are observed to aggregate rapidly when suspended in certain electrolytes (e.g., KCl), but rapidly separate in others (e.g., KOH) [24,29]. Despite much investigation, extant theoretical models [26,27] are unable to predict particle behavior a priori for a given electrolyte. A second and related complicating factor is that the separation distance between the colloidal particles and the electrode, i.e., the particle "height," is believed to affect the net magnitude of electrically induced flows around the particles [10,21], but the force balance controlling the particle height itself depends on the magnitude of the flow [28].…”

Section: Introductionmentioning

confidence: 99%

“…More recently, Dutcher et al used confocal microscopy to demonstrate that the average particle height is correlated with both the magnitude of the lateral flow as well as the effective particle diffusivity and consequent propensity to form disordered or hexatic aggregates [28]. Despite extensive investigation [22,23,26,27,29], however, extant theoretical models are unable to predict height and corresponding particle behavior a priori for a given electrolyte.…”

Section: Introductionmentioning

confidence: 99%

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Bifurcation in the Steady-State Height of Colloidal Particles near an Electrode in Oscillatory Electric Fields: Evidence for a Tertiary Potential Minimum

et al. 2015

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Application of an oscillatory electric field is known to alter the separation distance between micron-scale colloidal particles and an adjacent electrode. This behavior is believed to be partially due to a lift force caused by electrohydrodynamic flow generated around each particle, with previous work focused on identifying a single steady-state "height" of the individual particles over the electrode. Here, we report the existence of a pronounced bifurcation in the particle height in response to low-frequency electric fields. Optical and confocal microscopy observations reveal that application of a ∼100 Hz field induces some of the particles to rapidly move several particle diameters up from the electrode, while the others move closer to the electrode. Statistics compiled from repeated trials demonstrate that the likelihood for a particle to move up follows a binomial distribution, indicating that the height bifurcation is random and does not result from membership in some distinct subpopulation of particles. The fraction of particles that move up increases with increased applied potential and decreased frequency, in a fashion qualitatively consistent with an energy landscape predicated on competition between electrohydrodynamic flow, colloidal interactions, and gravitational forces. Taken together, the results provide evidence for the existence of a deep tertiary minimum in the effective electrode-particle interaction potential at a surprisingly large distance from the electrode.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Bifurcation in the Steady-State Height of Colloidal Particles near an Electrode in Oscillatory Electric Fields: Evidence for a Tertiary Potential Minimum

et al. 2015

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“…Complicating the understanding of particle behavior near an electrode are two additional observations, including an electrolyte effect, and a bimodal particle height distribution . Figure a quantifies the rate of aggregate formation, k E, for various electrolytes .…”

Section: Particle Assembly In Secondary Flowsmentioning

confidence: 96%

Polymer and Particle Dynamics and Assembly in Varied Hydrodynamic Fields

Ruud

Wilkinson

Dutcher

2016

Macro Chemistry & Physics

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Polymeric solutions and colloidal suspensions are complex fluidic mixtures featuring mesoscopic characteristic length scales. An exciting feature of complex fluids is their unusual response to external stimulus, such as mechanical, electrical, or chemical forcing, due to changes in the orientation, structure, and assembly of the dissolved or suspended macromolecules. These tunable polymer and particle dynamics and interactions play essential roles in both industrial and environmental aqueous processes. In this work, recent advancements in complex fluid dynamics and macromolecular assembly in varied hydrodynamic fields are highlighted, including viscoelastic (de)stabilization in Taylor–Couette flow, colloidal particle assembly in electrohydrodynamic flows, and polyelectrolyte–particle flocculation in turbulent flows. Polymers including neutral polyethylene oxide and charged cationic polyacrylamide and particles including charged spherical beads and smectite inorganic clays are explored here. Polymer–particle dynamics and assembly, if well understood, can be engineered for key contributions in environmental remediation and energy‐saving applications.

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The Impact of Stern‐Layer Conductivity on the Electrohydrodynamic Flow Around Colloidal Motors under an Alternating Current Electric Field

Yang

Johnson

2019

Advanced Intelligent Systems

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Particles under a perpendicularly applied alternating current (AC) electric field assemble into complex structures and exhibit tunable locomotion. Although they possess very similar physical properties, silica particles form two‐dimensional (2D) close‐packed crystals in deionized water, whereas polystyrene (PS) spheres repel each other. Using nanoparticle tracers, it is shown that the electrohydrodynamic (EHD) flow around silica particles is contractile, whereas it is extensile around PS particles. The Stern‐layer conductivities of PS and silica spheres are further measured experimentally and used in theoretical models to calculate the EHD flow surrounding them, which matches well with experiments. Therefore, the incorporation of Stern‐layer conductivity resolves the puzzle that EHD flow surrounding a particle with moderate zeta potentials is extensile. The impacts of zeta potential, Stern‐layer conductivity, salt concentration, and particle size on the EHD flow are examined herein. It is found that particles with high zeta potential, small diameter, or immersed in low salt concentration solutions tend to have extensile EHD flow surrounding them because the enhanced surface conductivity in the double layer makes the particles effectively more polarizable than the solvent. Herein, it is further shown that asymmetric EHD motors made from PS and silica particles exhibit behaviors that are consistent with the model predictions.

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Electrolyte dependence of particle motion near an electrode during ac polarization

Cited by 26 publications

References 33 publications

Bifurcation in the Steady-State Height of Colloidal Particles near an Electrode in Oscillatory Electric Fields: Evidence for a Tertiary Potential Minimum

Bifurcation in the Steady-State Height of Colloidal Particles near an Electrode in Oscillatory Electric Fields: Evidence for a Tertiary Potential Minimum

Polymer and Particle Dynamics and Assembly in Varied Hydrodynamic Fields

The Impact of Stern‐Layer Conductivity on the Electrohydrodynamic Flow Around Colloidal Motors under an Alternating Current Electric Field

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