Electric-?field-driven ionic transport on the nanoscale

Abstract

In this thesis, we study the behaviour of a fluid containing both positive and negative charged ions, when this electrolyte is forced by an external electric fi?eld through a conical nanopore with a negative charged wall, by solving the Poisson-Nernst-Planck-Stokes (PNPS) equations numerically. We fi?nd that an external potential difference over this nanopore causes ionic transport which creates an electric current. We ?find the ion densities, total electric current. velocity and total potential as a function of the potential difference over the nanopore by varying this quantity for two different length scales of the geometry. We consider length scales such that in one of the geometries the Debye layers, caused by the charged pore wall, do not overlap in the pore. In the other geometry, we choose length scales such that these layers overlap in the pore. We ?find that the asymmetry in the geometry causes asymmetries with respect to the potential difference and that the length scale of the geometry has a huge impact on these, quantitative, asymmetries. Furthermore, we surprisingly find that peaks in the difference between the density of the positively and negatively charged ions do not shift into the pore if we increase the half-angle.