Zero‐Depth Interfacial Nanopore Capillaries

Abstract

Charged molecules can translocate through the nanopore. The instant passage of the molecule momentarily impacts the conductance by locally reducing the aperture size of the channel. The resulting variations of the ionic conductance depends on the local topology of the translocating molecule; particularly, portions of long chain molecules such as polymers, proteins or DNA mark the electronic readout with specific conductance blockade fingerprints, and ultimately allow for reconstructing the sequence of monomers composing the translocating strands. [10] Consequently, thinner pores, i.e., capillaries with shorter channels, are capable of resolving shorter portions of molecules, leading for instance toward highresolution sequencing devices. [1] Thus, the challenge toward high-resolution sequencing has driven the development of ultrashort channel nanopores. Historically, two major classes of nanopores, i.e., biological and solid state nanopores, have been considered. The thickness of these nanopores varies from a few nanometers, as for α-hemolysin biological nanopores, [11,12] up to tens of nanometers for solid-state nanopores. [13] A revolutionary breakthrough aiming at reducing the capillary length of nanopores was achieved by the introduction of 2D materials such as graphene, [14][15][16] hexagonal boron nitride, [17] and molybdenum disulfide. [18][19][20][21] Indeed, the monoatomic capillary length of 2D nanopores is expected to offer sequencing capabilities, [2] but has not been realized yet. Inferior mechanical stability is one of the downsides of thin membranes inherently limiting the sustainability of 2D nanopores. Moreover, the complex fabrication process, involving cleanroom facilities and electron beam lithography, [22][23][24] can be demanding to scale up to industrial production. The noise levels in such devices are also orders of magnitude higher than those for long capillary-based nanopores, thus hindering their application for sequencing. [25] To address these issues, we introduce the concept of interfacial nanopores, generated at the crossing of two trenches, as illustrated in Figure 1. Fundamentally, the cross-section of two 1D straight lines is a zero-dimensional entity defined as a point (Figure 1a). The addition of a second dimensionality implies the overlap of two components to become a surface (Figure 1b). Similarly, in a 3D space, the interface shared between two tangent rectangular parallelepipeds is a surface, hence mathematically 2D (Figure 1c). Unlike nanopores commonly fabricated in 2D materials-which notwithstanding still possess a finite thickness-the surface defined by the crossing parallelepipeds is strictly 2D and thus does not exhibit any thickness. A High-fidelity analysis of translocating biomolecules through nanopores demands shortening the nanocapillary length to a minimal value. Existing nanopores and capillaries, however, inherit a finite length from the parent membranes. Here, nanocapillaries of zero depth are formed by dissolving two superimposed and crossing metallic nanoro...

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