Cyclic electrophoretic and chromatographic separation methods

Eijkel, Jan C.T.; Berg, Albert van den; Manz, Andreas

doi:10.1002/elps.200305750

Cited by 22 publications

(18 citation statements)

References 52 publications

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“…MHD-driven flow is of particular interest to chromatography as it allows one to drive fluid flow in a closed loop, in effect, providing an "infinitely long column" (Martin 1958;Eijkel et al 2004). In a traditional, linear, separation column, the column length must be selected in advance, which is not always feasible when dealing with unknown analytes or with analytes that have slightly different partition coefficients.…”

mentioning

confidence: 99%

When MHD-based microfluidics is equivalent to pressure-driven flow

Qin

Bau

2010

Microfluid Nanofluid

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Magnetohydrodynamics (MHD) provides a convenient, programmable means for propelling liquids and controlling fluid flow in microfluidic devices without a need for mechanical pumps and valves. When the magnetic field is uniform and the electric field in the electrolyte solution is confined to a plane that is perpendicular to the direction of the magnetic field, the Lorentz body force is irrotational and one can define a "Lorentz" potential. Since the MHD-induced flow field under these circumstances is identical to that of pressure-driven flow, one can utilize the large available body of knowledge about pressure-driven flows to predict MHD flows and infer MHD flow patterns. In this note, we prove the equivalence between MHD flows and pressure-driven flows under certain conditions other than flow in straight conduits with rectangular crosssections. We determine the velocity profile and the efficiency of MHD pumps, accounting for current transport in the electrolyte solutions. Then, we demonstrate how data available for pressure driven flow can be utilized to study various MHD flows, in particular, in a conduit patterned with pillars such as may be useful for liquid chromatography and chemical reactors. Additionally, we examine the effect of interior obstacles on the electric current flow in the conduit and show the existence of a particular pillar geometry that maximizes the current. solution is confined to a plane that is perpendicular to the direction of the magnetic field, the Lorentz body force is irrotational and one can define a "Lorentz" potential. Since the MHDinduced flow field under these circumstances is identical to that of pressure-driven flow, one can utilize the large available body of knowledge about pressure-driven flows to predict MHD flows and infer MHD flow patterns. In this note, we prove the equivalence between MHD flows and pressure-driven flows under certain conditions other than flow in straight conduits with rectangular cross-sections. We determine the velocity profile and the efficiency of MHD pumps, accounting for current transport in the electrolyte solutions. Then, we demonstrate how data available for pressure driven flow can be utilized to study various MHD flows, in particular, in a conduit patterned with pillars such as may be useful for liquid chromatography and chemical reactors. Additionally, we examine the effect of interior obstacles on the electric current flow in the conduit and show the existence of a particular pillar geometry that maximizes the current.

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mentioning

confidence: 99%

When MHD-based microfluidics is equivalent to pressure-driven flow

Qin

Bau

2010

Microfluid Nanofluid

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“…West et al 10 fabricated a MHD continuous flow microreactor with three thermal zones in an attempt to facilitate the thermocycling needed for DNA amplification. Eijkel et al 11 proposed a circular, open tubular chromatographic system based on the circular flow motion induced by MHD. Indeed, MHD propulsion is one of the few methods that allow pumping of liquids along a closed loop, thereby forming a conduit with an "infinite length.…”

Section: Introductionmentioning

confidence: 99%

Magnetohydrodynamic flow of RedOx electrolyte

Qian

Bau

2005

Physics of Fluids

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Magnetohydrodynamic MHD flow of a RedOx electrolyte in a straight conduit is investigated theoretically. Inert electrodes are deposited along segments of the opposing walls of a straight conduit that is filled with a RedOx electrolyte solution. The conduit is positioned in a uniform magnetic field. When a potential difference is applied across the opposing electrodes, the resulting current interacts with the magnetic field to induce Lorentz forces. The species' mass transport and the momentum equation are coupled and must be solved simultaneously. We compute the various species' concentration distributions, the current flux distribution, and the liquid's motion in the absence and presence of pressure gradients. The pressure gradients may either assist or oppose the MHD flow. At low potential differences, the current and the induced MHD flow increase nearly linearly as the potential difference increases. When the potential difference exceeds a certain critical value, the current and the flow rate saturate. We demonstrate that it is advantageous to use multiple electrode pairs with dielectric gaps between adjacent electrodes rather than a single electrode pair with an equivalent length. Finally, MHD flow with RedOx solution in the presence of abundant supporting electrolyte under limiting current conditions is analyzed using boundary layer theory. The approximate analytical solutions for the ions concentrations and the current agree well with the numerical solutions. Magnetohydrodynamic ͑MHD͒ flow of a RedOx electrolyte in a straight conduit is investigated theoretically. Inert electrodes are deposited along segments of the opposing walls of a straight conduit that is filled with a RedOx electrolyte solution. The conduit is positioned in a uniform magnetic field. When a potential difference is applied across the opposing electrodes, the resulting current interacts with the magnetic field to induce Lorentz forces. The species' mass transport and the momentum equation are coupled and must be solved simultaneously. We compute the various species' concentration distributions, the current flux distribution, and the liquid's motion in the absence and presence of pressure gradients. The pressure gradients may either assist or oppose the MHD flow. At low potential differences, the current and the induced MHD flow increase nearly linearly as the potential difference increases. When the potential difference exceeds a certain critical value, the current and the flow rate saturate. We demonstrate that it is advantageous to use multiple electrode pairs with dielectric gaps between adjacent electrodes rather than a single electrode pair with an equivalent length. Finally, MHD flow with RedOx solution in the presence of abundant supporting electrolyte under limiting current conditions is analyzed using boundary layer theory. The approximate analytical solutions for the ions' concentrations and the current agree well with the numerical solutions.

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“…The number of reports concerning microfluidic devices (chips, micro total analysis system or TAS) has increased dramatically since the initial concept was introduced some years ago [73,74]. In particular, microchip CE devices have been shown to offer many advantages over conventional CE systems: parallel channels in one device, reduced amounts of reagents and waste, increased precision and accuracy and the potential for disposable devices.…”

Section: Microfluidic Devicesmentioning

confidence: 99%

“…The concentration of cross-linking agent (%C) is 3.3% in all cases [70]. view sample introduction [76], cyclic electrophoretic and chromatographic separation methods [74] and theory and technology of TAS [77]. Two reviews report various applications of chips [78,79], including peptide and protein analysis.…”

Section: Microfluidic Devicesmentioning

confidence: 99%