Zeta potential of microfluidic substrates: 1. Theory, experimental techniques, and effects on separations

Kirby, Brian J.; Hasselbrink, Ernest F.

doi:10.1002/elps.200305754

Cited by 884 publications

(831 citation statements)

References 93 publications

(114 reference statements)

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“…While this is a good guide to experimental studies, we realize that the electrostatic potential within the channel is usually not of the form shown in Eq. (4) especially in the region where the ionic strength is very small [69].…”

Section: Discussionmentioning

confidence: 99%

Wall depletion length of a channel-confined polymer

Cheong

Dorfman

2017

Phys. Rev. E

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Numerous experiments have taken advantage of DNA as a model system to test theories for a channel-confined polymer. A tacit assumption in analyzing these data is the existence of a well defined depletion length characterizing DNA-wall interactions such that the experimental system (a polyelectrolyte in a channel with charged walls) can be mapped to the theoretical model (a neutral polymer with hard walls). We test this assumption using pruned-enriched Rosenbluth method (PERM) simulations of a DNA-like semiflexible polymer confined in a tube. The polymer-wall interactions are modeled by augmenting a hard wall interaction with an exponentially decaying, repulsive soft potential. The free energy, mean span, and variance in the mean span obtained in the presence of a soft wall potential are compared to equivalent simulations in the absence of the soft wall potential to determine the depletion length. We find that the mean span and variance about the mean span have the same depletion length for all soft potentials we tested. In contrast, the depletion length for the confinement free energy approaches that for the mean span only when depletion length no longer depends on channel size. The results have implications for the interpretation of DNA confinement experiments under low ionic strengths. * dorfman@umn.edu

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Section: Discussionmentioning

confidence: 99%

Wall depletion length of a channel-confined polymer

Cheong

Dorfman

2017

Phys. Rev. E

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“…It is known from the literature that the absolute value of the potential increases with dilution ͑Erickson et al, 2000;Gu and Li, 2000;Kirby and Hasselbrink, 2004͒, which results in a higher number of attracted counterions near the surface, neutralizing the fixed surface charge. This leads to a decrease in the fixed surface charge density with decreasing ionic strength.…”

Section: Nanochannel Conductancementioning

confidence: 99%

Transport phenomena in nanofluidics

2008

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The transport of fluid in and around nanometer-sized objects with at least one characteristic dimension below 100 nm enables the occurrence of phenomena that are impossible at bigger length scales. This research field was only recently termed nanofluidics, but it has deep roots in science and technology. Nanofluidics has experienced considerable growth in recent years, as is confirmed by significant scientific and practical achievements. This review focuses on the physical properties and operational mechanisms of the most common structures, such as nanometer-sized openings and nanowires in solution on a chip. Since the surface-to-volume ratio increases with miniaturization, this ratio is high in nanochannels, resulting in surface-charge-governed transport, which allows ion separation and is described by a comprehensive electrokinetic theory. The charge selectivity is most pronounced if the Debye screening length is comparable to the smallest dimension of the nanochannel cross section, leading to a predominantly counterion containing nanometer-sized aperture. These unique properties contribute to the charge-based partitioning of biomolecules at the microchannel-nanochannel interface. Additionally, at this free-energy barrier, size-based partitioning can be achieved when biomolecules and nanoconstrictions have similar dimensions. Furthermore, nanopores and nanowires are rooted in interesting physical concepts, and since these structures demonstrate sensitive, label-free, and real-time electrical detection of biomolecules, the technologies hold great promise for the life sciences. The purpose of this review is to describe physical mechanisms on the nanometer scale where new phenomena occur, in order to exploit these unique properties and realize integrated sample preparation and analysis systems.

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“…Figure 1 describes some of the main features of ITP boundaries dispersed by nonuniform EOF. Throughout this paper, we will assume negative EO mobility (typical for glass or silica for approximately pH 4 and above, see Kirby & Hasselbrink 2004) and anionic ITP, but the concepts are easily extended to cover cationic ITP and/or positive wall charge. Near the beginning of a typical ITP experiment, the high-conductivity LE fills most of the channel so that the axial-average EOF is dominated by the EO slip in the LE zone.…”

Section: Itp Dispersion Due To Eofmentioning

confidence: 99%

Sample dispersion in isotachophoresis

Garcia-Schwarz¹,

Bercovici²,

Marshall³

et al. 2011

J. Fluid Mech.

115

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We present an analytical, numerical and experimental study of advective dispersion in isotachophoresis (ITP). We analyse the dynamics of the concentration field of a focused analyte in peak mode ITP. The analyte distribution is subject to electromigration, diffusion and advective dispersion. Advective dispersion results from strong internal pressure gradients caused by non-uniform electro-osmotic flow (EOF). Analyte dispersion strongly affects the sensitivity and resolution of ITP-based assays. We perform axisymmetric time-dependent numerical simulations of fluid flow, diffusion and electromigration. We find that analyte properties contribute greatly to dispersion in ITP. Analytes with mobility values near those of the trailing (TE) or leading electrolyte (LE) show greater penetration into the TE or LE, respectively. Local pressure gradients in the TE and LE then locally disperse these zones of analyte penetration. Based on these observations, we develop a one-dimensional analytical model of the focused sample zone. We treat the LE, TE and LE-TE interface regions separately and, in each, assume a local Taylor-Aris-type effective dispersion coefficient. We also performed well-controlled experiments in circular capillaries, which we use to validate our simulations and analytical model. Our model allows for fast and accurate prediction of the area-averaged sample distribution based on known parameters including species mobilities, EO mobility, applied current density and channel dimensions. This model elucidates the fundamental mechanisms underlying analyte advective dispersion in ITP and can be used to optimize detector placement in detection-based assays.

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Zeta potential of microfluidic substrates: 1. Theory, experimental techniques, and effects on separations

Cited by 884 publications

References 93 publications

Wall depletion length of a channel-confined polymer

Wall depletion length of a channel-confined polymer

Transport phenomena in nanofluidics

Sample dispersion in isotachophoresis

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