Effects of Electroosmotic Flow on Ionic Current Rectification in Conical Nanopores

Abstract

The effects of electroosmotic flow (EOF) on the ionic current rectification (ICR) phenomenon in conical nanopores are studied comprehensively with use of a continuum model, composed of Nernst−Planck equations for the ionic concentrations, the Poisson equation for the electric potential, and Navier−Stokes equations for the flow field. It is found that the preferential current direction of a negatively charged nanopore is toward the base (tip) under a relatively high (low) κR t, the ratio of the tip radius size to the Debye length. The direction also changes with the charge polarity of the nanopore. The EOF effect on the ionic current rectification ratio in a conical nanopore becomes noticeable at an intermediate κR t and surface charge density of the nanopore, meanwhile increasing significantly with the applied voltage.

Diffusiophoresis of an Elongated Cylindrical Nanoparticle along the Axis of a Nanopore

“…The mathematical model and its implementation with COMSOL have been extensively validated by comparing its results of electroosmotic, electrophoretic, and diffusioosmotic flows with the corresponding approximate analytical solution and experimental results obtained from the literature. [17,[55][56][57][58]61] In this section, we present a few numerical results of the diffusiophoretic motion of a charged elongated cylindrical nanoparticle in a nanopore as functions of the imposed concentration ratio, a, the ratio of the particle size to the EDL thickness, ka p , the dimensionless surface charge density of the particle, " s p , the particle aspect ratio, L p /a p , the ratio of the pore size to the particle's size, a/a p , the dimensionless surface charge density of the nanopore, " s w , and the type of salt. To show the effect of the induced electrophoresis driven by the generated electric field, E diffusivity , arising from the difference in the ionic diffusivities, salts KCl and NaCl at temperature T = 300 K are used.…”

Electrokinetic particle translocation through a nanopore containing a floating electrode

“…The floating electrode is not electrically excited which is in contrast to the gate electrode employed in our previous field effect control of DNA translocation through a nanopore. A multi-ion model (MIM) composed of the coupled Poisson-NernstPlanck (PNP) equations for the ionic mass transport and the Mingkan Zhang 1 modified Stokes equations for the flow field have been employed to study the ionic current rectification in a nanopore [31][32][33]. The results show good agreements with the experiment data.…”

“…The numerical simulation of DNA translocation is implemented by solving the electric field, the ionic [31][32][33]36]; while the fluid flow is governed by the modified Stokes equations as the inertial terms are negligible due to a very small Reynolds number in this study. The governing equations are normalized based on the bulk concentration c 0 as the ionic concentration scale, f 0 5 R U T/F as the potential scale, the particle radius a as the length scale, u 0 ¼ eR…”

“…It has been confirmed that all the results are mesh-independent. The mathematical model and its implementation with COMSOL have been validated by testing many benchmark problems, as discussed in our previous studies [33,36]. We also simulate the electrophoresis of a sphere translocating along the axis of an uncharged dielectric cylindrical nanopore, whose analytical solution is available when the zeta potential of the particle is relatively small and the EDL of the particle is not disturbed by the external electric field, flow field and the solid boundary [44].…”

Electroosmotic flow in single PDMS nanochannels

“…In microchannels, the thickness of EDL is generally very small and is negligible in comparison with the channel size in most cases. However, as the dimensions of nanochannels are comparable with the thickness of EDL, EDLs may overlap and consequently many new transport phenomena such as current rectification [1][2][3][4] , ion enrichment and depletion 5 , new dynamics of pressure driven flow [6][7][8] have been discovered. These new transport phenomena facilitate various novel applications and studies of the nanofluidics [9][10][11][12] .…”