Electrokinetic particle translocation through a nanopore containing a floating electrode

Abstract

Electrokinetic particle translocation through a nanopore containing a floating electrode is investigated by solving a continuum model, composed of the coupled Poisson-Nernst-Planck (PNP) equations for the ionic mass transport and the modified Stokes equations for the flow field. Two effects due to the presence of the floating electrode, the induced-charge electroosmosis (ICEO) and the particle-floating electrode electrostatic interaction, could significantly affect the electrokinetic mobility of DNA nanoparticles. When the electrical double layers (EDLs) of the DNA nanoparticle and the floating electrode are not overlapped, the particle-floating electrode electrostatic interaction becomes negligible. As a result, the DNA nanoparticle could be trapped near the floating electrode arising from the induced-charge electroosmosis when the applied electric field is relatively high. The presence of the floating electrode attracts more ions inside the nanopore resulting in an increase in the ionic current flowing through the nanopore; however, it has a limited effect on the deviation of the current from its base current when the particle is far from the pore.

Induced-charge electro-osmotic flow around cylinders with various orientations

“…After grid independ ence study, it is decided that second-order elements are utilized with a number of 20,000, which are suitable for the current simulations. The author refers to Zhang et al, 30 which has similar electrokin etic flow study including detailed systematic grid reso lution work.…”

The Influence of Electric Field Intensity and Particle Length on the Electrokinetic Transport of Cylindrical Particles Passing through Nanopore

“…On the basis of successfully preparing nanopores, other researchers further investigated the movement of DNA using nanopores made of SiO 2 [ 17 ], alumina film [ 18 ], graphene nanopore [ 19 ], molybdenum disulfide [ 20 ], and glass capillary [ 21 , 22 ]. To complement experimental investigations demanding complex preparation processes of solid nanopores and expensive detection equipment, a large number of researchers have applied the continuum model [ 23 , 24 , 25 , 26 , 27 ], molecular dynamics [ 28 , 29 , 30 ], atomic level Brownian dynamics [ 31 ], Brownian kinematics [ 32 ] to carry out numerical simulation on particle motion and ion current change in nanopores.…”

Slowing down DNA translocation through a nanopore by lowering fluid temperature

“…Since the size of fluid reservoirs is usually much larger than that of the nanopore, the local electric field within the nanopore is significantly higher than that in the fluid reservoir, resulting in slow particle motion within the fluid reservoir and high translocation velocity inside the nanopore. One of the major challenges in the nanopore‐based technique is that DNA nanoparticles translocate through the nanopore too fast to be accurately detected . Although one can reduce the voltage bias applied across the nanopore to reduce the electric field inside the nanopore and consequently slow down the DNA translocation, lower voltage bias will simultaneously reduce the capture rate of the nanopore and the magnitude of the current change, leading to lower throughput and read‐out accuracy.…”

“…Therefore, a relatively high voltage bias is typically applied across the nanopore in the nanopore‐based DNA sequencing applications. To now, several methods have been proposed to slow down the DNA translocation through the nanopore to achieve higher read‐out accuracy . They include increasing the solvent viscosity to increase the viscous drag force on the particle, lowering the fluid temperature to increase the fluid viscosity, adjusting salt concentration and/or salt type to modify the charge property of the nanopore by chemical functionalization of the nanopore or by an ionic field effect transistor, imposing a salt concentration gradient, utilizing optical tweezers, and conducting nanopores .…”