Figure 2.

(A–C) Finite element simulations of the current density for a potential difference of 1 V between the nanoelectrodes, without (A, dashed line in C) and with (B, solid line in C) insulation. The nanopore is 5 nm in diameter, the electrodes are 2-nm high, 5-nm wide, and have flat faces terminating at the pore edge. Each nanoelectrode is 2-μm long. The insulation (if present) is 3-nm thick and covers all but the end face of the nanoelectrodes. The solution conductivity is 1 S/m. Note that the vertical axis is the same for (A–C). (D) Diagram showing how plots (A–C) are oriented. (A, B) are plots on the dark plane intersecting the membrane. The lighter rectangle on this plane is a projection of the electrode cross-section. The fraction of the total current flowing through this rectangle is quoted in the text. The curves in (C) are plots on the dashed line running along the nanopore axis. (E) TEM image of nanoelectrodes with titanium dioxide insulation. The contrast of this image is amplified to highlight the titanium dioxide layer. (F) Leakage current for uninsulated (blue squares) and insulated (red circles) electrodes, with the low leakage in the latter case highlighted in the left inset. The right inset shows the measurement configuration. This measurement was carried out in 1 M KCl, 10 mM Tris, 1 mM EDTA, pH 8.5.