Transverse Detection of DNA in a MoS2 Nanopore

Abstract

Solid-state nanopores can be used for single-molecule detection and potentially provide a platform for rapid DNA sequencing. DNA molecules along with water and ions are electrophoretically driven through a small orifice in a membrane. The ionic current blockade is measured and provides information about the size and the length of the molecule. Typically, solid-state nanopores are fabricated in relatively thick material (20nm), thus not providing single-base resolution. Recently, monolayer materials such as MoS2 have proven very useful in detecting and differentiating single nucleotides. Compared to e.g. graphene, monolayer MoS2 is an intrinsic semiconductor with a bandgap of 1.8eV and can thus be used to fabricate a field effect transistor. Here we show that a nanopore in monolayer MoS2 can be integrated with a two-dimensional field-effect transistor. We report simultaneous and correlated detection of the ionic current trace and the transverse sheet current through suspended MoS2 during DNA translocation. Signal-to-noise ratios in the sheet current are superior to ionic current and seem to follow a different sensing principle. During translocation through the nanopore, the negative charge of DNA decreases the drain-source conductance of the n-type semiconductor, effectively gating the semiconductor. Such a device configuration might overcome resolution limitations due to the dominating access-resistance in ionic current through ultra-thin membranes. Furthermore, this technology provides a simple way of parallelization: An array of nanopores can be created on the same membrane without the need of fabricating individually addressable microfluidic chambers. The ionic voltage would then just act as the driving force of bringing the molecules to the field-effect transistor and all detection is done on the transistors. Further work is required in order to better understand the sensing principle and establish the resolution of these new devices.