Unbalanced Ion Flushing Effect in MoS2 Nanopore Biosensors

Abstract

In MoS2 nanopores, in addition to the widely measured ionic current signal to detect DNA nucleotides or epigenetic malformations, recent efforts have focused on the use of the transverse electronic current along the membrane for biomolecules sensing. This approach provides larger current magnitude and allows detection at the observed DNA translocation speed in the solid-state nanopore, which are crucial for accurate biomolecule sensing and faster DNA sequencing. As of today, no existing model is able to relate the variations of the transverse current to the interaction between ions, biomolecules and the MoS2 membrane. In this presentation, we report a comprehensive transport model based on the Poisson-Boltzmann transport formalism that considers the effect of biomolecules, electrolyte, and ion screening on conducting carriers along a MoS2 membrane. By accounting for membrane geometry and material properties used in recent experiment, we are able to extract the different electrical contributions to the transverse current variation during a DNA translocation event. In particular, we show that the major contribution to the electrical signal is caused by an unbalanced-ion-flushing effect that arises when the ion double-layer around the nanopore edge is swept out of the pore by the biomolecule translocation. By optimizing the MoS2 membrane geometry and nanopore size, we predict higher sensitivity to detect the translocation event in the corresponding transverse current signal. Thus,the identification of the unbalanced ion effect on the transverse electronic current foresees a critical new direction to improving the signal-to-noise ratio in solid-state nanopore sensing device.