Papers by Keyword: Electrodiffusion

Abstract: The recently developed bombardment induced ion transport (BIIT) technique is reviewed. BIIT is based on shining an energy-selected alkali ion beam at the surface of a sample of interest. Attachment of these ions leads to the build-up of a surface potential and a surface particle density. This in turn generates the corresponding gradients which induce ion transport towards a single metal electrode connected to the backside of the sample where it is detected as a neutralization current. Two different versions of BIIT are presented, i.) the native ion BIIT and ii.) the foreign ion BIIT. The former is demonstrated to provide access to absolute ionic conductivities and activation energies, the latter leads to the generation of electrodiffusion profiles. Theoretical modelling of these concentration profiles by means of the Nernst-Planck-Poisson theory allows to deduce the concentration dependence of diffusion coefficients.

Abstract: The paper provides a physical description of ionic transport through the rigid symmetrical channel. A three-dimensional mathematical model, in which the ionic transport is treated as the electrodiffusion of ions, is presented. The model bases on the solution of the 3D Nernst-Planck-Poisson system for cylindrical geometry. The total flux includes drift (convection) and diffusion terms. It allows simulating the transport characteristics at the steady-state and time evolution of the system. The numerical solutions of the coupled differential diffusion equation system are obtained by finite element method. Examples are presented in which the flow characteristics at the stationary state and during time evolution are compared. It is shown that the stationary state is achieved after about 2×10 ^-8 s since the process beginning. Various initial conditions (channel charging and dimensions) are considered as the key parameters controlling the selectivity of the channel. The model allows determining the flow characteristic, calculating the local concentration and potential across the channel. The model can be extended to simulate transport in polymer membranes and nanopores which might be useful in designing biosensors and nanodevices.

Abstract: Motivation for this work comes from the application of the inverse method to electrochemical systems. The basic process operating in these systems is electrodiffusion, which can be described by the full form of the Nernst-Planck and Poisson equations. No simplification like electroneutrality assumption is used. Numerical procedure based on the method of lines (MLs) for time dependent electrodiffusion transport is presented with any number of ionic species. The resulting system of ODEs is effectively solved by employing different integrators (Radau IIA, Rosenbrock, SEULEX). Selected electrochemical systems (liquid junction, bi-ionic case, ion selective electrodes (ISE)) are treated. Performance of the integrators is compared.

Abstract: Ion transport across the membrane of the living cell (molecular ion channels) is a critical process, e.g., the triggering of nerve cells and heart muscle cells is coupled with mechanisms controlled by ion diffusion (electrodiffusion). Although the process is described by the century old Nernst- Planck-Poisson system of equations, it is not well understood and a clear understanding of how the interaction between channel and ions affects the flow is still missing. We present a three-dimensional model of the molecular channel. An appropriate quantitative description of the ion transport process allows proper explanation of molecule channel interactions (e.g. the ions flow for a given concentration gradient should depend on the potential and other parameters describing the interaction, i.e. asymmetric transport). We show the simulation of the stationary electrodiffusion in the ion channel showing radial symmetry.