Double‐layer polarization of a non‐conducting particle in an alternating current field with applications to dielectrophoresis

Zhao, Hui

doi:10.1002/elps.201100035

Cited by 42 publications

(41 citation statements)

References 106 publications

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“…The discussions on the frequency dependence have been documented in our previous works in details. 27 Here, we do not repeat them. Instead, we focus on electrostatic correlations.…”

Section: Resultsmentioning

confidence: 97%

On the Impact of Electrostatic Correlations on the Double-Layer Polarization of a Spherical Particle in an Alternating Current Field

Alidoosti

Zhao

2018

Langmuir

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At concentrated electrolytes, the ion-ion electrostatic correlations effect is considered an important factor in electrokinetics. In this paper, we compute, in theory and simulation, the dipole moment for a spherical particle (charged, dielectric) under the action of an alternating electric field using the modified continuum Poisson-Nernst-Planck (PNP) model by Bazant et al. (Phys. Rev. Lett. 106, 2011).1 We investigate the dependency of the dipole moment in terms of the frequency and its variation with such quantities like zeta potential, electrostatic correlation length, and double layer thickness. With thin electric double layers, we develop simple models through performing an asymptotic analysis to the modified PNP model. We also present numerical results for an arbitrary Debye screening length and electrostatic correlation length. From the results, we find a complicated impact of electrostatic correlations on the dipole moment. For instance, with increasing the electrostatic correlation length, the dipole moment decreases and reaches a minimum, and then it goes up. This is because of initially decreasing of surface conduction and its finally increasing due to the impact of ion-ion electrostatic correlations on ion’s convection and migration. Also, we show that in contrast to the standard PNP model, the modified PNP model can qualitatively explain the data from the experimental results in multivalent electrolytes.

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“…The discussions on the frequency dependence have been documented in our previous works in details. 27 Here, we do not repeat them. Instead, we focus on electrostatic correlations.…”

Section: Resultsmentioning

confidence: 97%

On the Impact of Electrostatic Correlations on the Double-Layer Polarization of a Spherical Particle in an Alternating Current Field

Alidoosti

Zhao

2018

Langmuir

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“…Each sphere i with radius R i is located at the position r i . The polarizability of the sphere i can be expressed as α i = 4π« 0 «R 3 i K i , where K i is the polarization coefficient that can be calculated both analytically (42) and numerically (43). Two spheres representing the lobes on the same dimer are subject to the geometric constraint of fixed bond length L = r i − r j .…”

Section: Significancementioning

confidence: 99%

Electric-field–induced assembly and propulsion of chiral colloidal clusters

Ma¹,

Wang²,

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

180

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Chiral molecules with opposite handedness exhibit distinct physical, chemical, or biological properties. They pose challenges as well as opportunities in understanding the phase behavior of soft matter, designing enantioselective catalysts, and manufacturing single-handed pharmaceuticals. Microscopic particles, arranged in a chiral configuration, could also exhibit unusual optical, electric, or magnetic responses. Here we report a simple method to assemble achiral building blocks, i.e., the asymmetric colloidal dimers, into a family of chiral clusters. Under alternating current electric fields, two to four lying dimers associate closely with a central standing dimer and form both right-and left-handed clusters on a conducting substrate. The cluster configuration is primarily determined by the induced dipolar interactions between constituent dimers. Our theoretical model reveals that in-plane dipolar repulsion between petals in the cluster favors the achiral configuration, whereas outof-plane attraction between the central dimer and surrounding petals favors a chiral arrangement. It is the competition between these two interactions that dictates the final configuration. The theoretical chirality phase diagram is found to be in excellent agreement with experimental observations. We further demonstrate that the broken symmetry in chiral clusters induces an unbalanced electrohydrodynamic flow surrounding them. As a result, they rotate in opposite directions according to their handedness. Both the assembly and propulsion mechanisms revealed here can be potentially applied to other types of asymmetric particles. Such kinds of chiral colloids will be useful for fabricating metamaterials, making model systems for both chiral molecules and active matter, or building propellers for microscale transport.hirality is a fundamental concept presented ubiquitously in the molecular world. For example, small molecules such as the amino acids, phospholipids, and sugars with specific handedness build many biomacromolecules whose chirality is essential to living organisms. Although the right-and left-handed molecules are identical in chemical composition, the catalytic activity (1), pharmacological impact (2, 3), biological recognition (4), and optical response (5) can be strikingly different. Extending the chiral structure to microscopic objects such as colloids has become increasingly desirable for several reasons. First, the chiral arrangement of colloidal particles can exhibit unusually strong optical, electric, and magnetic responses (6-10) that are not manifested either at the single-particle level or in achiral forms. Therefore, chiral clusters can be potentially used to build metamaterials (11-14) with exotic properties or sensors for detection of molecules. Second, chiral particles can be conveniently characterized by real-time optical microscopy. As the macroscopic analog of chiral molecules, they can be used to study fundamental questions related to the crystallization (15) or enantiomeric separation (16, 17) of a racemic...

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“…25, p. 10). 26 Particles that exhibit pDEP move to high electric field regions and particles that exhibit nDEP move to low electric field regions. 2,15 This motion up and down electric field gradients is described by the Clausius-Mossotti factor for spherical particles,…”

Section: Introductionmentioning

confidence: 99%

Frequency sweep rate dependence on the dielectrophoretic response of polystyrene beads and red blood cells

2013

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Alternating current (AC) dielectrophoresis (DEP) experiments for biological particles in microdevices are typically done at a fixed frequency. Reconstructing the DEP response curve from static frequency experiments is laborious, but essential to ascertain differences in dielectric properties of biological particles. Our lab explored the concept of sweeping the frequency as a function of time to rapidly determine the DEP response curve from fewer experiments. For the purpose of determining an ideal sweep rate, homogeneous 6.08 lm polystyrene (PS) beads were used as a model system. Translatability of the sweep rate approach to $7 lm red blood cells (RBC) was then verified. An Au/Ti quadrapole electrode microfluidic device was used to separately subject particles and cells to 10Vpp AC electric fields at frequencies ranging from 0.010 to 2.0 MHz over sweep rates from 0.00080 to 0.17 MHz/s. PS beads exhibited negative DEP assembly over the frequencies explored due to Maxwell-Wagner interfacial polarizations. Results demonstrate that frequency sweep rates must be slower than particle polarization timescales to achieve reliable incremental polarizations; sweep rates near 0.00080 MHz/s yielded DEP behaviors very consistent with static frequency DEP responses for both PS beads and RBCs. V C 2013 AIP Publishing LLC.

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Double‐layer polarization of a non‐conducting particle in an alternating current field with applications to dielectrophoresis

Cited by 42 publications

References 106 publications

On the Impact of Electrostatic Correlations on the Double-Layer Polarization of a Spherical Particle in an Alternating Current Field

On the Impact of Electrostatic Correlations on the Double-Layer Polarization of a Spherical Particle in an Alternating Current Field

Electric-field–induced assembly and propulsion of chiral colloidal clusters

Frequency sweep rate dependence on the dielectrophoretic response of polystyrene beads and red blood cells

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