We next investigated CVC characteristics obtained at a planar Au electrode as a function of the concentration of Tris buffer. Resistance dictated by ion transport to the electrode can be observed in a CVC. the IDZ is expected to extend symmetrically from the embedded cathode. Based on qualitative evaluation of these micrographs, the planar Au device exhibits larger fluid vortices, indicated by a larger radius of curvature in the distorted IDZ boundary (Figure ). In the Ag/Au device (Figure ), smaller vortices are observed (many vortices with small radius of curvature) and the IDZ boundary has a more uniform shape. In the PSC/Ag/Au device (Figure ), the IDZ boundary had a stable, plug-like shape, and it was maintained within the secondary bead bed over the duration of the experiment. This attribute is significant because propagation of the IDZ boundary complicates the alignment of an enriched plug of analyte to a detector or other functional device component (e.g., droplet generator).