Transport of charged samples in fluidic channels with large zeta potentials

Dutta, Debashis

doi:10.1002/elps.200700013

Cited by 20 publications

(14 citation statements)

References 27 publications

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“…As a consequence of the transverse ion distributions produced by the electric fields inside EDLs, the mean ion speed (zone velocity) $\bar{u}_{i}$ in nanofluidics becomes dependent on the ion charge z i and is given by 7–18 where $\bar{u}_{{i{\rm {p}}}}$ and $\bar{u}_{{i{\rm {e}}}}$ denote, respectively, the mean ion speed due to pressure‐driven fluid flow and electroosmotic fluid flow, $\langle \cdots \rangle = (n + 1)\mathop{\int}_0^a {( \cdots )(y/a)^{n} {\rm {d}}(y/a)}$ signifies the cross‐sectional area‐average ( n =0 or 1) and B i =exp(− z i Ψ) characterizes the Boltzmann distribution of ions in the transverse direction. In nanochannel electrophoresis, no pressure gradient is applied so that $\bar{u}_{{i{\rm {p}}}} = 0$ .…”

Section: Theorymentioning

confidence: 99%

“…fluid flow in nanochannels, which has been growing exponentially over the past decade 1–5. In nanoscale channels where the hydraulic diameter is comparable to the electrical double layer (EDL) thickness, the enormous electric fields inside EDL produce transverse ion distributions that depend on the ion charge 6–10. As a consequence, the non‐uniform fluid flow along nanochannels, which may be electric field‐driven 11, 12 or pressure‐driven 11–14, yields charge‐dependent mean ion speeds enabling the separation of ions by charge alone.…”

Section: Introductionmentioning

confidence: 99%

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Ion separation in nanofluidics

Xuan

2008

Electrophoresis

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Ionic species with a constant charge-to-size ratio (i.e. electrophoretic mobility) cannot be separated in electroosmotic or pressure-driven flow along microscale channels. In nanoscale channels, however, the enormous electric fields inside electrical double layers cause transverse ion distributions yielding charge-dependent mean ion speeds in the flow. Those ions with a constant charge-to-size ratio can thus be separated solely by charge (or equivalently, size) in nanofluidics. Here we develop an analytical model to optimize and compare the separation of such ions in nanochannel chromatography and nanochannel electrophoresis in terms of selectivity, plate height and resolution. Both planar and cylindrical geometries are considered. It is found that in nanoscale channels chromatography yields a larger selectivity and a larger minimum reduced plate height than electrophoresis does. The maximum resolution is, however, comparable between these two nanofluidic approaches, where the optimal channel half-height or tube radius is within the range of 1-10 times the Debye length. Our results also suggest that cations can be better separated in nanofluidics than can anions.

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Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ion separation in nanofluidics

Xuan

2008

Electrophoresis

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“…3 will likely be reduced by a factor on the order of two. Similar considerations arise for electroosmomotic flow [14,15,37], and as such the results in Fig. 3 should be viewed as qualitative in nature and representing an upper bound on the attainable resolution.…”

Section: Local Optimization For a Single Speciesmentioning

confidence: 71%

“…Since these early studies, theoretical and numerical investigations have explored in more detail various aspects of this new technique, including dispersion [11][12][13], impact of the z potential [14], channel geometry [15], hindered diffusion [16] and nonlinear field affects due to the finite size of macromolecules [17]. Despite this continued interest, however, only a few studies [16][17][18][19] have reported the capabilities of the process, as measured by peak resolution, and only a handful have addressed the factors that determine this.…”

Section: Introductionmentioning

confidence: 99%

Optimization of charged species separation by autogenous electric field‐flow fractionation in nano‐scale channels

Griffiths¹,

Nilson²

2010

Electrophoresis

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Numerical methods are employed to examine the resolution and optimization of a relatively new technique for charged species separation that is based on flow along nano-scale channels having an electric double-layer thickness comparable to the channel size. In such channels, the electric field inherent to the double-layer produces transverse species distributions that depend on the species charge. Flow along the channel thus yields mean axial species speeds that also depend on the species charge, enabling species separation and identification. Building on earlier work describing retention and plate heights, here we characterize this new type of field-flow fractionation via the classic metric of resolution. Sample results are presented and discussed for a wide range of conditions for both pressure-driven and electroosmotic flows. Optimum design and operating conditions are also examined. We find that resolution is maximized for optimum values of the zeta potential and Debye layer thickness and that these optima depend strongly on the species charge or range of charges of interest. Under optimum conditions, acceptable resolution can be obtained over a wide range of species charges for pressure-driven flows. This separable range of charges is much smaller for electroosmotic flows. Finally, sample calculations are presented showing that all species in the range of charge between -8 to 10 can be separated simultaneously with resolutions above unity, and this is possible in less than 6 s under optimum conditions that are readily achievable.

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“…Without using the Boltzmann equation, Qu et al [34] derived new governing equations for the overlapped EDL fields, its results showed that the modified model predicts a lower electric potential in the EDL field than the classical theory. Using the different models, Dutta [35,36] presented the electroosmotic transport through rectangular channels with small and large zeta potentials by Taylor-Aris dispersivity, respectively. The results showed that if zeta potential was large enough that there were overlapped EDL fields, the mean velocity and the slug dispersivity can vary as much as an order of magnitude comparing with small zeta potential.…”

Section:  mentioning

confidence: 99%

Mixed electroosmotic-pressure driven multi-fluid flow in microchannels

Li¹

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Microfluidic and Lab-on-a-chip devices have attracted great interest over the last decade due to the advantages such as increased efficiency, throughput, portability, reduced analysis time, reagent consumption and cost. Comparing with a number of techniques (e.g., pressure, centrifuge, and thermal gradient driven flow), electroosmosis has been used to induce electroosmotic flow to transport, separate, and mix samples. This thesis addresses the following four topics: (1) Three-fluid flow in straight microchannels based on the combined effect of hydrodynamic and electroosmosis with planar interface; (2) Modeling of tunable optofluidic lens based on the combined effect of hydrodynamic and electroosmosis; (3) Semi-analytical model of mixed electroosmotic/pressure-driven two immiscible fluids with curved interface ; (4) The linear stability of two-fluid flow in a During my study at Nanyang Technological University, lots of professors, staff and friends helped me in various ways. I wish to express my sincere gratitude to these friends. Firstly and foremost, I wish to express my sincere gratitude and hearty thanks to my supervisor Associate Professor Wong Teck Neng. During my study and research work, Prof. Wong provides excellent guidance, patient encouragement and support. I would like to express my sincere gratitude and hearty thanks to Associate Professor Nguyen Nam-Trung for his kind help in my whole research work. I wish to express my deep gratitude to Mr. Yuan Kee Hock for the valuable assistance of my experiment. I am also grateful to the graduate and FYP students, my friends in the Thermal and Fluid Research Lab for their help whenever needed. During my PhD study, my wife Liu Haili has been very supportive. Her unconditional support has given me the strength to finish my study. I am much indebted to my wife for all her love and support. I also would like to acknowledge the Research Scholarship provided by Nanyang Technological University.

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Transport of charged samples in fluidic channels with large zeta potentials

Cited by 20 publications

References 27 publications

Ion separation in nanofluidics

Ion separation in nanofluidics

Optimization of charged species separation by autogenous electric field‐flow fractionation in nano‐scale channels

Mixed electroosmotic-pressure driven multi-fluid flow in microchannels

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