Dielectric layer modulated nanofluidic transport: Formation of parent–sister vortices

Abstract

Our analysis, consistent with the induced-charge electrokinetic, aptly discusses the effect of gate potential on the formation of vortices of disparate scales in a nanofluidic channel. The nanochannel considered here is connected with reservoirs at its ends, while a pair of dielectric gate electrodes is also embedded on the outer layer of the channel wall. In this endeavor, we establish that a suitable modulation of the dielectric polarization and inherent surface charge of the channel wall leads to the development of pair of “parent–sister” vortices in the flow field alongside yields a net flow in the channel, as well a unique fluidic functionality achieved at small scale is reported here for the first time. Moreover, we identify for the first time that the critical value of surface charge density (“critical-sigma,” i.e., σc) for two different typical heights of the nanofluidic channel, leading to the formation of maximum strength and size vortices by ceasing the net throughput. Also, we establish a critical range of surface charge density for a window of an arbitrary dimension of the dielectric gate electrode—a range for which optimum vortices are generated in the pathway, simultaneously producing adequate net flow through the channel. Under the present modeling configuration, we obtain that |σc|∼O(1 mC/m2) for a 1 μm long nanochannel having embedded quartz layer gate electrodes with gate potential |Vg|∼O(1 V). We believe that critical-sigma would be a crucial parameter for the design and fabrication of state-of-the-art nanodevices/nanosystems intended for augmented fluidic functionalities, for example, efficient solute mixing.