Origin of nonequilibrium 1/f noise in solid-state nanopores†
Nanopore devices are applied in many fields such as molecular sensing and DNA sequencing, and the detection precision is primarily determined by 1/f noise. The mechanism of 1/f noise in nanopores is still not clearly understood, especially the nonequilibrium 1/f noise in rectifying nanopores. Hereby, we propose that 1/f noise in solid-state nanopores originates from the electrolyte ion trapping–detrapping process occurring on the inner surface of the nanopores, which can nonlinearly affect the ion number inside the rectifying nanopores due to the specific ion enrichment/depletion effect. Our model can not only quantitatively explain the nonlinear dependence of 1/f noise on the applied voltage, i.e., the nonequilibrium 1/f noise, for current rectifying nanopores, but also provide a unified explanation on the influence of the electrolyte concentration, pH value, and geometry of the nanopores. From our model, we observe a new flattening phenomenon of 1/f noise in conical nanopores, and this is further confirmed by our experimental results. Our research can be helpful in understanding and reducing 1/f noise in other nanopore devices, especially where the enrichment or depletion of ions exists.