Diffusiophoresis of a highly charged dielectric fluid droplet

Wu, Yvonne; Jian, Elaine; Fan, Leia; Tseng, Jessica; Wan, Renee; Lee, Eric

doi:10.1063/5.0069778

Cited by 22 publications

(25 citation statements)

References 49 publications

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“…The generation of this exterior vortex flow is kinetic energy-consuming. The more viscous the droplet is, the less kinetic energy is spun off the droplet due to its higher momentum inertia [20,21]. As a result, the faster it moves.…”

Section: Resultsmentioning

confidence: 99%

“…It is this fundamental electrostatic difference of whether there is a tangent electric driving force spinning the charged droplet surface that distinguishes the electrokinetic responses of the two types of droplets to the external field force: Electrokinetic Maxwell spinning traction is present on a dielectric droplet surface, which is absent for a conducting droplet. That is where the various fascinating and unique features of a dielectric droplet come from, such as the more viscous a droplet is, the faster it may move, and the "solidification" phenomenon where all the droplets move like a rigid particle at identical speeds regardless of their viscosities [20,21]. The electrokinetic behavior of a conducting droplet is much simpler compared with a dielectric droplet.…”

Section: Introductionmentioning

confidence: 99%

“…The electrokinetic behavior of a conducting droplet is much simpler compared with a dielectric droplet. Lee and his coworkers have conducted a series of theoretical studies on the phoretic motions of highly charged droplets, both dielectric and conducting, and both electrophoresis and diffusiophoresis, based on a pseudo-spectral method numerically [20][21][22][23][24][25]. In addition, a general analytical formula is obtained valid for weakly charged droplets under the Debye-Hückel approximation.…”

Section: Introductionmentioning

confidence: 99%

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Electrophoresis of a highly charged fluid droplet in dilute electrolyte solutions: Analytical Hückel‐type solution

et al. 2022

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An analytical formula is presented here for the electrophoresis of a dielectric or perfectly conducting fluid droplet with arbitrary surface potentials suspended in a very dilute electrolyte solution. In other words, when the Debye length (κ −1 ) is very large, or κa≪1, where κ is the electrolyte strength and a stands for the droplet radius. This formula can be regarded as an extension of the famous Hückel solution valid for weakly charged rigid particles to arbitrarily charged fluid droplets. The formula reduces successfully to the ones obtained by Booth for a dielectric droplet, and Ohshima for a perfectly conducting droplet, both under Debye-Hückel approximation valid for weakly charged droplets. Moreover, the formula is valid for a gas bubble and a rigid solid particle as well. Classic results obtained by Hückel for a rigid particle are reproduced as well. We found that for a dielectric droplet, the more viscous the droplet is, the faster it moves regardless of its surface potential, contrary to the intuition based on the purely hydrodynamic consideration. For a perfectly conducting liquid droplet, on the other hand, the situation is reversed: The less viscous the droplet is, the faster it moves. The presence or absence of the spinning electric driving force tangent to the droplet surface is found to be responsible for it. As a result, an axisymmetric exterior vortex flow surrounding the droplet is always present for a dielectric liquid droplet, and never there for a conducting liquid droplet.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrophoresis of a highly charged fluid droplet in dilute electrolyte solutions: Analytical Hückel‐type solution

et al. 2022

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“…In our present study we consider the fixed viscosity and dielectric permittivity of the ambient aqueous medium, and the results are presented varying the dielectric permittivity of the droplet. Note that the dielectric permittivities of hydrocarbon droplet, 57 nonpolar solvent, 58 dielectric oil, 59 gas bubbles, 23 etc. are much smaller than that of the aqueous medium.…”

Section: Analytic Expression For Electrophoretic Mobilitymentioning

confidence: 99%

Electrophoresis of Dielectric and Hydrophobic Spherical Fluid Droplets Possessing Uniform Surface Charge Density

2022

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The present article deals with the theoretical study on electrophoresis of hydrophobic and dielectric spherical fluid droplets possessing uniform surface charge density. Unlike the ideally polarizable liquid droplet bearing constant surface ζ-potential, the tangential component of the Maxwell stress is nonzero for dielectric fluid droplets with uniform surface charge density. We consider the continuity of the tangential component of total stress (sum of the hydrodynamic and Maxwell stresses) and jump in dielectric displacement along the droplet-to-electrolyte interface. The typical situation is considered here for which the interfacial tension of the fluid droplet is sufficiently high so that the droplet retains its spherical shape during its motion. The present theory can be applied to nanoemulsions, hydrophobic oil droplets, gas bubbles, droplets of immiscible liquid suspended in aqueous medium, etc. Based on weak field and low charge assumptions and neglecting the Marangoni effect, the resultant electrokinetic equations are solved using linear perturbation analysis to derive the closed form expression for electrophoretic mobility applicable for the entire range of Debye−Huckel parameter. We further deduced an alternate approximate expression for electrophoretic mobility without involving exponential integrals. Besides, we have derived analytical results for mobility pertaining to various limiting cases. The results are further illustrated to show the impact of pertinent parameters on the overall electrophoretic mobility.

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“…As for the diffusiophoresis of colloidal entities in general, there has been a surge of novel applications reported in recent years [17][18][19][20][21][22]. Theoretical explorations on the underneath electrokinetic mechanisms for various types of particles, such as the dielectric droplets, were conducted by Lee and his coworkers very recently as well, with potential applications in drug delivery and enhanced oil recovery [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Diffusiophoresis in suspensions of highly charged soft particles

et al. 2022

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Diffusiophoresis phenomenon of aoft particles suspended in binary electrolyte solutions is explored theoretically in this study based on the spherical cell model, focusing on the chemiphoresis component in absence of diffusion potential. Both the electrostatic and hydrodynamic aspects of the boundary confinement, or steric effect, due to the presence of neighboring particles are examined extensively under various electrokinetic conditions. Significant local extrema are found in mobility profiles expressed as functions of the Debye length in general, synchronized with the strength of the motion-inducing double layer polarization. Moreover, a seemingly peculiar phenomenon is observed that the soft particles may move faster in more concentrated suspensions. The competition between the simultaneous enhancement of the motion-inducing electric driving force and the motion-retarding hydrodynamic drag force from the boundary confinement effect of the neighboring particles is found to be responsible for it. The above findings are also demonstrated experimentally in a very recent study on the diffusiophoretic motion of soft particles through porous collagen hydrogels. The results presented here are useful in various practical applications of soft particles like drug delivery.

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Diffusiophoresis of a highly charged dielectric fluid droplet

Cited by 22 publications

References 49 publications

Electrophoresis of a highly charged fluid droplet in dilute electrolyte solutions: Analytical Hückel‐type solution

Electrophoresis of a highly charged fluid droplet in dilute electrolyte solutions: Analytical Hückel‐type solution

Electrophoresis of Dielectric and Hydrophobic Spherical Fluid Droplets Possessing Uniform Surface Charge Density

Diffusiophoresis in suspensions of highly charged soft particles

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