A theoretical model that considers both the diffusion and electrical osmosis fluxes to estimate the diffusion current through a nanochannel was proposed. The equivalent impedance of a nanochannel was modelled as a series connection of finite resistor–capacitor circuits. The impedances of the electrical double layer and buffer solution in each infinitesimal RC circuit were represented using a capacitor and a resistor, respectively. The diffusion-induced current in the proposed model was position dependent due to the electrical double layer effect. Computer simulations and experiments using a nanoporous anodic aluminum oxide thin film as the filter to separate electrolysis with an ion concentration gradient were conducted. Electrochemical impedance spectroscopy was performed to measure the impedance of the porous anodic aluminium oxide thin film in the frequency domain such that the capacitor and resistor could be estimated accordingly. A high degree of coincidence between the theoretical and experimental data was observed.

Modeling Ion Diffusion Current in Nanochannel Using Infinitesimal Distribution Resistor–Capacitor Circuits. M.C.Chien, G.J.Wang, W.C.Yu: Japan Journal of Applied Physics, 2007, 46, 7436-40