Electrokinetics over charge-modulated surfaces in the presence of patterned wettability: role of the anisotropic streaming potential.

In the present study, we focus on evaluating the induced streaming electric field along the orthogonal directions in a narrow fluidic confinement in the presence of patterned surface wettability and modulated surface charges. We attempt to assess the implications of such modulations on the related important quantities and pinpoint the regimes of improved induced streaming potential field and the resulting anisotropy in the induced potential. Our results reveal that for certain combinations of the parameters characterizing the modulated slip, a significant amount of augmentation in the streaming electric field might be obtained, whereas in other cases the effects may lead to adverse consequences. We further demonstrate that the presence of anisotropic modulations on the channel walls give rise to considerable off-diagonal effects, which makes the streaming potential "disoriented" with the applied pressure gradient, when the same is not applied along one of the orthogonal directions. Our analysis also shows that one can remove such "mis-orientations" by finely tuning several relevant flow and geometric parameters, which may bear immense scientific and technological consequences towards an improved design of miniaturized energy conversion devices.