Asymmetrical multiphase front propagation and localized oscillations in a reaction-migration iron electrodissolution model with microfluidic flow cell geometry

Abstract

We study nonlinear patterns in a reaction-migration system in microfluidic flow cell geometry with potentiostatic metal electrodissolution by using one- and two-variable electrode kinetics to model bistable, excitable, and oscillatory dynamics. On long electrodes in flow channel geometry, which is often used in lab-on-chip devices, the propagation of activity front (in the bistable region) was found to be a strongly asymmetrical, complex, multiphase process, with the onset of spontaneous secondary inactivation waves. On segmented electrodes, because of strong coupling, the activation front can hop over insulating segments. A common feature of bistable and excitable dynamics is that the front initiation from the remote (high resistance) edge is easier (requires less perturbation) compared to the close (low resistance) edge. In the oscillatory region, we found spatially localized oscillations located on the close part of the electrode, with oscillation properties depending on cell geometry parameters. The flow cell geometry induces large changes in the local resistance along the electrodes in the flow channel, especially between the remote and close edges; this variation creates largely heterogeneous dynamical units, whose coupling accounts for many features of the observed complex behavior.