Thermophoresis of charged colloidal particles in aqueous media – Effect of particle size

Zhou, Yi; Yang, Chun; Lam, Yee Cheong; Huang, Xiaoyang

doi:10.1016/j.ijheatmasstransfer.2016.05.109

Cited by 24 publications

(22 citation statements)

References 50 publications

(119 reference statements)

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“…Here, we perform a qualitative analysis based on the preceding discussion of 1 µm particles to clarify the roles of dielectrophoresis and thermophoresis in the enrichment of 5 µm particles. The conclusions from several previous works 48 , 55 , 56 suggested that the Soret coefficient of 5 µm particle is larger than that of 1 µm particle. However, the diffusivity of 5 µm particle is smaller than that of 1 µm particle by a factor of 5.…”

Section: Resultsmentioning

confidence: 83%

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Electrokinetically driven continuous-flow enrichment of colloidal particles by Joule heating induced temperature gradient focusing in a convergent-divergent microfluidic structure

Zhao

Song

et al. 2017

Sci Rep

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Enrichment of colloidal particles in continuous flow has not only numerous applications but also poses a great challenge in controlling physical forces that are required for achieving particle enrichment. Here, we for the first time experimentally demonstrate the electrokinetically-driven continuous-flow enrichment of colloidal particles with Joule heating induced temperature gradient focusing (TGF) in a microfluidic convergent-divergent structure. We consider four mechanisms of particle transport, i.e., advection due to electroosmosis, electrophoresis, dielectrophoresis and, and further clarify their roles in the particle enrichment. It is experimentally determined and numerically verified that the particle thermophoresis plays dominant roles in enrichment of all particle sizes considered in this study and the combined effect of electroosmosis-induced advection and electrophoresis is mainly to transport particles to the zone of enrichment. Specifically, the enrichment of particles is achieved with combined DC and AC voltages rather than a sole DC or AC voltage. A numerical model is formulated with consideration of the abovementioned four mechanisms, and the model can rationalize the experimental observations. Particularly, our analysis of numerical and experimental results indicates that thermophoresis which is usually an overlooked mechanism of material transport is crucial for the successful electrokinetic enrichment of particles with Joule heating induced TGF.

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Section: Resultsmentioning

confidence: 83%

“…According to Eq. (7) in Supplementary Information, one then expects that the thermophoretic velocity of 5 µm particle is comparable to that of 1 µm particle 55 . On the other hand, it is known that the dielectrophoretic force is scaled to the cubic power of particle size (see Eq.…”

Section: Resultsmentioning

confidence: 98%

Electrokinetically driven continuous-flow enrichment of colloidal particles by Joule heating induced temperature gradient focusing in a convergent-divergent microfluidic structure

Zhao

Song

et al. 2017

Sci Rep

Self Cite

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“…Eslamian et al [38] demonstrated that using a nanofluid in bottom-heated laminar natural convection results in a considerable increase in heat transfer rate and thermophoresis force is a significant contributor to heat transfer augmentation, particularly for high Ra numbers. In experimental study of Zhou et al [39], a microfluidic device was used to directly observe and quantitatively characterize the thermophoretic behaviors of charged hydrophobic polystyrene particles within a wide diameter range from 100 nm to 5 lm dispersed in deionized water. As a result of particle size effect on the thermophoresis of such particles, the increase in particle size was found to not only alter the direction of thermophoretic motion, but also linearly increase the thermophoretic velocity.…”

Section: Resultsmentioning

confidence: 99%

“…It has been indicated that the dielectric constant p e is 1.00059 for air, 4.3 for quartz, 80.0 for pure water, and is infinite for conducting particles. Actually, equations (39) and (40) are obtained by modifying the earliest expressions presented in Whitby and Liu [33]. Their calculated results demonstrated that the diffusion charging was a predominant mechanism for charging particles less than 0.2 m µ in diameter, even in the presence of an electrostatic field.…”

Section: Physical Description Of Charging Mechanismsmentioning

confidence: 99%

Adaptation of Surface Rejuvenation Model to Turbulent Mass Transfer with Coupling Between Thermophoretic and Coulombic Force Interactions

Chiou¹

2018

ENGMATH

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Development and applications of the surface rejuvenation model for particle transport towards the surface through turbulent boundary layer involve (1) the introduction of the constitutive equations to establish relations between the fluxes involved in mass transfer processes and the respective driving potentials, (2) the use of definition of the convective velocity to separate the mass transfer flux into diffusive and convective components based on Eulerian models of turbulent deposition proposed by Guha [1] and Young and Leeming [2], (3) the introduction of exponentially distributed functions given by Danckwerts [3] to transform the instantaneous transport properties into the mean domain prior to the solution of the conservation equations, and finally (4) the use of developed relationships for the mean concentration profile and mass transfer flux to obtained an analytical solution for the mean deposition velocity of neutral and charged particles. The deposition velocity of neutral particles with and without including thermophoretic effect is first calculated and then used to clarify the effects caused by the presence of external imposed electric field. A comparison with the experimental data and other theoretical predictions shows that the surface rejuvenation model is logical in finding the combined effect of thermophoresis and turbophoresis on the deposition of neutral particles and confirming the relative independence of deposition velocity upon these drift mechanisms at high values of particle inertia. When both thermophoretic and Coulombic forces operate together, two important conclusions are obtained from this model: (1) the contribution to particle deposition velocities does not represent the sum of these drift mechanisms considered in isolation; (2) the turbophoresis induces an additional drift velocity toward the wall in the vicinity of the wall, alleviating these external forces and enhancing particle deposition onto the wall through reduced build-up of particle concentration adjacent to the wall.

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“…Note that all new thermophoretic micron-scale devices that operate under a microscope using optical laser heating [ 23 , 39 , 43 ], a channel geometry [ 43 , 45 , 76 ] or diffusion cell have not been validated by comparing the results with the benchmark values [ 97 ]. The reason is that the modern methods using a microscope to monitor the concentration profile or to analyze the particle velocity, require colloids of larger macromolecules with fluorescent labels, while concentration changes of the benchmark systems (organic solvents) [ 97 ] cannot be monitored with these microscope methods.…”

Section: Micron-scale Devicesmentioning

confidence: 99%

Thermophoretic Micron-Scale Devices: Practical Approach and Review

Lee

Wiegand

2020

Entropy

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In recent years, there has been increasing interest in the development of micron-scale devices utilizing thermal gradients to manipulate molecules and colloids, and to measure their thermophoretic properties quantitatively. Various devices have been realized, such as on-chip implements, micro-thermogravitational columns and other micron-scale thermophoretic cells. The advantage of the miniaturized devices lies in the reduced sample volume. Often, a direct observation of particles using various microscopic techniques is possible. On the other hand, the small dimensions lead to some technical problems, such as a precise temperature measurement on small length scale with high spatial resolution. In this review, we will focus on the “state of the art” thermophoretic micron-scale devices, covering various aspects such as generating temperature gradients, temperature measurement, and the analysis of the current micron-scale devices. We want to give researchers an orientation for their development of thermophoretic micron-scale devices for biological, chemical, analytical, and medical applications.

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Thermophoresis of charged colloidal particles in aqueous media – Effect of particle size

Cited by 24 publications

References 50 publications

Electrokinetically driven continuous-flow enrichment of colloidal particles by Joule heating induced temperature gradient focusing in a convergent-divergent microfluidic structure

Electrokinetically driven continuous-flow enrichment of colloidal particles by Joule heating induced temperature gradient focusing in a convergent-divergent microfluidic structure

Adaptation of Surface Rejuvenation Model to Turbulent Mass Transfer with Coupling Between Thermophoretic and Coulombic Force Interactions

Thermophoretic Micron-Scale Devices: Practical Approach and Review

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