Ion transport and current noise dynamics in conical nanopores

In this paper we develop numerical model to understand ion transport and current noise characteristics in conical nanopores. We extend the model that works in cylindrical nanopore. The model has steady state current term for potassium K⁺ ion, I_K⁺ = q_K⁺ u/L_nanopore + m_K⁺ au/V, where q_K⁺ is the potassium ion charge, u is the velocity of the ions, L_nanopore is the length of the conical nanopore, m_K⁺ is the mass of potassium ions, a is the acceleration of the ions and V is the voltage. The high frequency potassium ion noise current inside the conical nanopore is modelled as I_highK+ = √(4k GTB) where k is Boltzmann constant, G is the conductance of conical nanopores, T is the temperature and B is frequency. The low frequency potassium ion noise current is modelled as I_lowK+ = A/f where A is the charge carrier and f is the frequency term. The total potassium current with noise is I_totalK+ = q_K⁺ u/L_nanopore + m_K⁺ au/V + √(4kGTB) + A/f. The chloride ion current is simulated in our study. Here the simulation current matches experiments of conical nanopores for 1 M potassium chloride electrolyte solution. The applied voltage is 0.85 V. The power spectral density gives the 1/f noise as seen in experiments.