Effects of access resistance on the resistive-pulse caused by translocating of a nanoparticle through a nanopore

Abstract

Recent experimental studies showed that the access resistance (AR) of a nanopore with a low thickness-todiameter aspect ratio plays an important role in particle translocation. The existing theories usually only consider the AR without the presence of particles in the pore systems. Based on the continuum model, we systematically investigate the current change caused by nanoparticle translocation in different nanopore configurations. From numerical results, an analytical model is proposed to estimate the influence of the AR on the resistive-pulse amplitude, i.e., the ratio of the AR to the pore resistance. The current change is first predicted by our model for nanoparticles and nanopores with a wide range of sizes at the neutral surface charge. Subsequently, the effect of surface charges is studied. The results show that resistive-pulse amplitude decreases with the increasing surface charge of the nanoparticle or the nanopore. We also find that the shape of the position-dependent resistive-pulse might be distorted significantly at low bulk concentration due to concentration polarization. This study provides a deep insight into the AR in particle-pore systems and could be useful in designing nanopore-based detection devices.

Biphasic Resistive Pulses and Ion Concentration Modulation during Particle Translocation through Cylindrical Nanopores

“…The neglected particle effect on access resistance also contributed to the error. 37 As shown in Figure 6a, with the increase of pore length from 10 to 100 nm (corresponding to D/L from 3 to 0.3), the normalized peak current deviation increases. It is due to the larger ion concentration depletion/enhancement effect for longer pores when the particle is at the entrance/exit as shown in Figure 6, parts b and Figure c.…”

“…To achieve accurate results, the mesh resolution is high enough and the reservoir size in the model was increased to ensure that no change in calculated current and ion concentration was observed. 37 The particle is assumed to translocate through the pore along the symmetric axis, and thus the influence of particle deviation from the axis on the ionic current is neglected. Poisson−Nernst−Planck (PNP) equations and the Navier−Stokes (NS) equation were coupled to solve the ionic current and ion concentration with the commercial software Comsol Multiphysics.…”

Simulation analysis of nanopore performance in single-nanoparticle detection

“…The equivalent circuit derived from the device is shown in Fig.1(b). The whole circuit can be considered as serially connected resistances, including the geometric resistance inside the nanopore and access resistance on either side of membrane [4]. Therefore, when the DC voltage 0 is applied, the resulted current I can be expressed as:…”

“…From previous study, the access resistance is usually considered as a constant in either open state or blocked state if the shape of pore and the conductivity of electrolyte are determined [5]. Therefore, the resistance variation can be calculated with Equation (2) for both states [4]:…”

Discrimination of equi-sized nanoparticles by surface charge state using low-aspect-ratio pore sensors

“…17 In addition, Wang and colleagues 18 addressed this effect theoretically and indicated the low aspect ratio nanopore is more sensitive to the surface charge density of nanoparticle surface than the non-low aspect ratio one. 18 The smaller I p than I cal would thus indicate significant contributions of countercations on the PS particle surface to increase the number of current-carrying ionic carriers that compensate the pore resistance increase via the volume exclusion effect upon passing through the low-AR pore.…”