Electrical charging of a conducting water droplet in a dielectric fluid on the electrode surface

Jung, Yong-Mi; Oh, Hyun-Chang; Kang, In Seok

doi:10.1016/j.jcis.2008.04.019

Cited by 91 publications

(111 citation statements)

References 10 publications

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“…The effects of droplet size on the droplet velocity have been studied in systems with parallel electrodes without significant dielectrophoretic effects. 20,24 The droplet velocity always monotonously increased with growing droplet radius in the interval from 300 μm to 700 μm. As it was shown, the amount of electric charge is approximately proportional to R 2 (the power varied from 1.59 to 2.3 in different situations).…”

Section: Qualitative Predictions Of the Mathematical Modelmentioning

confidence: 96%

“…As it was shown, the amount of electric charge is approximately proportional to R 2 (the power varied from 1.59 to 2.3 in different situations). 20,24 …”

Section: Qualitative Predictions Of the Mathematical Modelmentioning

confidence: 99%

“…[20][21][22][23][24][25][26] Jung et al 24 and Im et al 20,22 studied the oscillatory migration of charged water droplets between two parallel electrodes. Oscillatory motion was also recorded for falling water droplets between parallelplated electrodes.…”

Section: Introductionmentioning

confidence: 99%

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Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

et al. 2014

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We experimentally observed oscillatory motion of water droplets in microfluidic systems with coplanar microelectrodes under imposed DC electric fields. Two-electrode arrangement with no bipolar electrode and eight-electrode arrangement with six bipolar microelectrodes were investigated. Kerosene was used as the continuous phase. We studied the dependences of the oscillation frequency on the electric field intensity and ionic strength of the water phase. We found that the electric field dependence is strongly nonlinear and discussed possible reasons of this phenomenon, e.g., the droplet deformation at electrode edges that affects the charge transfer between the electrode and droplet or the interplay between the Coulomb force on free charge and the dielectrophoretic force. Our experiments further revealed that the oscillation frequency decreases with growing salt concentration in the two-electrode arrangement, but increases in the eight-electrode arrangement, which was attributed to surface tension related processes and electrochemical processes on the bipolar electrodes. Finally, we analyzed the effects of the electric field on the oscillatory motion by means of a simplified mathematical model. It was shown that the electric force imposed on the droplet charge is the key factor to induce the oscillations and the dielectrophoretic force significantly contributes to the momentum transfer at the electrode edges. For the same electric field strength, the model is able to predict the same oscillation frequency as that observed in the experiments.

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Section: Qualitative Predictions Of the Mathematical Modelmentioning

confidence: 96%

“…As it was shown, the amount of electric charge is approximately proportional to R 2 (the power varied from 1.59 to 2.3 in different situations). 20,24 …”

Section: Qualitative Predictions Of the Mathematical Modelmentioning

confidence: 99%

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Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

et al. 2014

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“…Jung et al [97] studied the electrical charging of a water droplet at a copper electrode in silicone oil and considered the effects of the electric field, viscosity of the oil and the droplet size. Rhythmic motion of water droplets was observed and it was reported that the amount of electrical charging increased with the electric field strength and the droplet size.…”

Section: Water Droplet Electrophoresis 13mentioning

confidence: 99%

Charge of water droplets in non-polar oils

Schoeler

Josephides

Sajjadi

et al. 2013

Journal of Applied Physics

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Recent advances in droplet manipulation methods by electric fields and signals require a deeper understanding of water droplet charge. In this paper, we have investigated the electrophoretic motion of individual water microdroplets injected into non-polar silicone and paraffin oil by video optical microscopy on an individual droplet basis to determine droplet charge. It was found that the initial surface charge density of surfactant free droplets directly after injection from a micropipette is positive and of the order of 10−6 C/m2, regardless of pH and ion concentration in the range from pH 4 to pH 10 and from 0.01 mmol/l to 1.5 mol/l, respectively. The experimental results together with molecular dynamics simulations show that the nature and polarity of the charge can be explained by anisotropic orientation of water molecules at the interface rather than selective adsorption of ions. Furthermore, we showed that slip at the liquid-liquid boundary must be taken into account when interpreting electrophoretic measurements of droplets.

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“…3 Numerous studies [3][4][5][6][7][8][9][10][11][12][13] have reported various modes of droplet motion between electrodes using both experimental and numerical methods. A droplet behaves as an electrical charge-carrier between a pair of electrodes in an oil medium as an insulator.…”

Section: Introductionmentioning

confidence: 99%

Rotary motion of a micro-solid particle under a stationary difference of electric potential

Kurimura

Mori

Miki

et al. 2016

The Journal of Chemical Physics

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The periodic rotary motion of spherical sub-millimeter-sized plastic objects is generated under a direct-current electric field in an oil phase containing a small amount of anionic or cationic surfactant. Twin-rotary motion is observed between a pair of counter-electrodes; i.e., two vortices are generated simultaneously, where the line between the centers of rotation lies perpendicular to the line between the tips of the electrodes. Interestingly, this twin rotational motion switches to the reverse direction when an anionic surfactant is replaced by a cationic surfactant. We discuss the mechanism of this self-rotary motion in terms of convective motion in the oil phase where nanometer-sized inverted micelles exist. The reversal of the direction of rotation between anionic and cationic surfactants is attributable to the difference in the charge sign of inverted micelles with surfactants. We show that the essential features in the experimental trends can be reproduced through a simple theoretical model, which supports the validity of the above mechanism.

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Electrical charging of a conducting water droplet in a dielectric fluid on the electrode surface

Cited by 91 publications

References 10 publications

Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

Oscillatory motion of water droplets in kerosene above co-planar electrodes in microfluidic chips

Charge of water droplets in non-polar oils

Rotary motion of a micro-solid particle under a stationary difference of electric potential

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