Generalized Noise Study of Solid-State Nanopores at Low Frequencies

Abstract

Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study low-frequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nm-thick SiN x membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.

Adsorption Kinetics in Open Nanopores as a Source of Low-Frequency Noise

“…Experimentally, the noise spectrum is measured typically to scale as S(f ) ∼ 1/f α at low frequency f , with an exponent α ∼ 0.5 − 1.5. This behavior was reported in artificial nanopores and nanotubes with various shapes and materials [2][3][4][5][6][7][8][9][10][11] , but also in biological membranes 12,13 . This low-frequency noise does reduce the signal-to-noise ratio and impedes translocation measurement methods relying on the detection of the modulation of an electrical ionic current accompanying the passage of a macromolecule through a nanopore [14][15][16] .…”

High fidelity moving Z-score based controlled breakdown fabrication of solid-state nanopore

“…at 1 Hz which makes the nanopore suitable for single molecule sensing experiments. This f 1/ characteristic at low frequencies was comparable to these in previous studies [57][58][59][60].…”

1/f noise in solid-state nanopores is governed by access and surface regions

“…Smeets et al [31] established that 1/f noise in nanopores obeys Hooge's empirical equation which relates the noise to the number of charge carriers in the pore volume. Wen et al [38] further investigated the 1/f noise in solid-state nanopores, by analyzing pore-surface and pore-cylinder 1/f noise contributions as a function of pH and salt concentration. However, despite some success in describing the 1/f noise behaviour at different electrolyte conditions, none of these models so far has been able to quantitatively account for the 1/f noise for different nanopore geometries and membrane materials.…”