Electrokinetic sample transport in a microchannel with spatial electrical conductivity gradients

Studies of the sample transport in a microchannel with the electrical conductivity gradient are critical to develop techniques for on-chip sample transport control. A numerical model presented in this paper, consisting of the electrical potential equation, full Navier–Stokes equation and species conservation equation, is used to simulate sample transport in a microchannel with the consideration of the conductivity gradient. There are two situations studied here, sample pumping (where sample separation is minimized by employing a high-conductivity buffer in the sample region), and sample stacking (where sample separation is expedited by using a low-conductivity buffer as the sample carrier). The effects of applied electrical potential, sample diffusion coefficient and the ratio of conductivity of the driving buffer over the sample carrying buffer are investigated by using the developed model.

Graphical abstractCenterline axial concentration profiles for the transport of a two-analyte sample, where the conductivity of the sample-carrying buffer is higher than that of the driving buffer (pumping protocol).Figure optionsDownload full-size imageDownload as PowerPoint slide