1/f Noise in Solid-state Nanopore: Generation Mechanism and Prevention Methods

To realize DNA sequencing with solid-state nanopore, reduction of an ionic current noise is an important issue. Especially, low-frequency (1/f) noise causes a serious problem reducing read accuracy of DNA sequencing. Its origin has been heavily debated, but not yet clarified.
In this research, we found that 1/f noise is generated from the surface charge fluctuations due to an exchange reaction of alkali metal ions (M+) and protons (H+) on a nanopore wall. We hypothesized the charge fluctuations are dependent on the equilibrium constants of the reaction, and measured baseline current with various cations. Surprisingly, the order of 1/f noise intensity follows the theoretical one estimated from their equilibrium constants.
We also developed a new 1/f noise reduction method by suppressing the exchange reaction. The nanopore wall was coated with divalent cations, which lead to prevent the adsorption of other ions because those adsorption affinity is higher than other ions. As a result, we successfully and effectively reduced 1/f noise with this method.