Long-range transport and directed assembly of charged colloids under aperiodic electrodiffusiophoresis

Wang, Kun; Leville, Samuel; Behdani, Behrouz; Batista, Carlos

doi:10.1039/d2sm00631f

Cited by 7 publications

(25 citation statements)

References 58 publications

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“…These frequencies are only a few times larger than the critical frequency for Faradaic processes to occur (calculated according to ref to be a few hundred Hertz in 100 μM KCl). Moreover, water electrolysis has been reported under experimental conditions similar to those used here even though bubbles were not observed . Confirmation of the possible contribution of EDP in our experiments requires careful measurement of pH gradients, accurate modeling of the electrochemical reactions at the electrodes, and possibly blocking the electrode surface to minimize electrochemical reactions.…”

Section: Resultssupporting

confidence: 70%

“…Recently, it was reported , that 2 μm polystyrene (PS) microspheres suspended in HCl or NaOH aqueous solutions levitated from the surface of an electrode in an AC electric field oscillating at 100 Hz and of 40 V/cm. Later, similar colloidal levitation was achieved in NaSCN aqueous solutions under 1 kHz AC electric fields . These observations suggest that AC levitation could be developed into a generic tool for manipulating colloids in 3D.…”

Section: Introductionmentioning

confidence: 54%

“…An alternative mechanism is the recently proposed aperiodic EDP . The key idea is that electrochemical reactions occurring at the electrode surface generate long-range pH gradients, as convincingly demonstrated by the author of ref . As a result, electrically charged colloidal particles move via electrolyte diffusiophoresis to the point of highest pH, where they are trapped.…”

Section: Resultsmentioning

confidence: 97%

“…Later, similar colloidal levitation was achieved in NaSCN aqueous solutions under 1 kHz AC electric fields. 15 These observations suggest that AC levitation could be developed into a generic tool for manipulating colloids in 3D. Such AC levitation of colloidal particles was surprising, and a number of mechanisms were proposed to explain it including electrohydrodynamic (EHD) flows, 13 asymmetric rectified electric fields (AREFs), 16 and aperiodic electrodiffusiophoresis (EDP) 15 (see Results and Discussion for details).…”

Section: ■ Introductionmentioning

confidence: 99%

“…15 These observations suggest that AC levitation could be developed into a generic tool for manipulating colloids in 3D. Such AC levitation of colloidal particles was surprising, and a number of mechanisms were proposed to explain it including electrohydrodynamic (EHD) flows, 13 asymmetric rectified electric fields (AREFs), 16 and aperiodic electrodiffusiophoresis (EDP) 15 (see Results and Discussion for details). On the other hand, there is little information on the practical usefulness and limitations of using AC levitation as a technique to manipulate colloidal matter.…”

Section: ■ Introductionmentioning

confidence: 99%

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Dielectrophoretic Colloidal Levitation by Electrode Polarization in Oscillating Electric Fields

Chen

Peng

et al. 2023

Langmuir

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Controlled colloidal levitation is key to many applications. Recently, it was discovered that polymer microspheres were levitated to a few micrometers in aqueous solutions in alternating current (AC) electric fields. A few mechanisms have been proposed to explain this AC levitation such as electrohydrodynamic flows, asymmetric rectified electric fields, and aperiodic electrodiffusiophoresis. Here, we propose an alternative mechanism based on dielectrophoresis in a spatially inhomogeneous electric field gradient extending from the electrode surface micrometers into the bulk. This field gradient is derived from electrode polarization, where counterions accumulate near electrode surfaces. A dielectric microparticle is then levitated from the electrode surface to a height where the dielectrophoretic lift balances gravity. The dielectrophoretic levitation mechanism is supported by two numerical models. One model assumes point dipoles and solves for the Poisson–Nernst–Planck equations, while the second model incorporates a dielectric sphere of a realistic size and permittivity and uses the Maxwell-stress tensor formulation to solve for the electrical body force. In addition to proposing a plausible levitation mechanism, we further demonstrate that AC colloidal levitation can be used to move synthetic microswimmers to controlled heights. This study sheds light on understanding the dynamics of colloidal particles near an electrode and paves the way to using AC levitation to manipulate colloidal particles, active or passive.

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Section: Resultssupporting

confidence: 70%

Section: Introductionmentioning

confidence: 54%

Section: Resultsmentioning

confidence: 97%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Dielectrophoretic Colloidal Levitation by Electrode Polarization in Oscillating Electric Fields

Chen

Peng

et al. 2023

Langmuir

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Artificial chemotaxis under electrodiffusiophoresis

Silvera Batista,

Wang,

Blake

et al. 2025

Journal of Colloid and Interface Science

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Continuous Focusing of Particles by AC-Electroosmosis and Induced Dipole Interactions

Wiegerinck,

Wood,

Eijkel

et al. 2024

Langmuir

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Continuous particle focusing by using microfluidics is an effective method for separating particles, cells, or droplets for analytical purposes. Previously, it was shown that an alternating current across rectangular microchannels with slightly deformed side walls results in vortex flow patterns caused by alternating current electroosmosis (AC-EOF) and could lead to particle focusing. In this work, we explore this mechanism by experimentally studying the particle focusing behavior for various fluid flow velocities through a microchannel. Since it is unlikely that the particles are kept in their focused position solely by convection, a theoretical force balance between the hydrodynamic and the induced dipole force was determined. In our experiments, it was found that there is no substantial effect of the pressure-driven fluid velocity on the particle focusing velocity within the studied range. From the theoretical force balance calculations, it was determined that while the addition of the induced dipole force can still not completely describe the experimentally observed particle focusing, the induced dipole can be strong enough to overcome the hydrodynamic force. Finally, it is hypothesized that under specific circumstances, including a repulsive electrostatic force between a particle and electrode wall can complete the theoretical particle focusing force balance. Alternative phenomena that could also play a role in particle focusing are proposed.

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Long-range transport and directed assembly of charged colloids under aperiodic electrodiffusiophoresis

Abstract: Faradaic reactions often lead to undesirable side effects during the application of electric fields. Therefore, experimental designs often avoid faradaic reactions by working at low voltages or at high frequencies,...

Cited by 7 publications

References 58 publications

Dielectrophoretic Colloidal Levitation by Electrode Polarization in Oscillating Electric Fields

Dielectrophoretic Colloidal Levitation by Electrode Polarization in Oscillating Electric Fields

Artificial chemotaxis under electrodiffusiophoresis

Continuous Focusing of Particles by AC-Electroosmosis and Induced Dipole Interactions

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