A numerical investigation of an electroosmotic flow through a microchannel is presented. Lattice Poisson-Boltzmann method was utilized to determine the effective geometrical and electrokinetic parameters in a microfluidic system. The non-Newtonian fluid model is assumed to be viscoplastic which is suitable for modeling biologic structures. These types of fluids are shown to have a yield stress which affects the velocity profile significantly. Unlike Casson fluid constitutive properties, electrokinetic parameters are shown not to be effective on the yielded region in the microchannel. The influence of flow and viscokinetic parameters on yield height, plug-flow velocity and mass flow rate was studied and discussed.

A T-shaped microfluidic micro-mixer was designed to mix desired concentrations of two fluid streams and to prepare their homogenous mixture solution. A hydrostatic pressure gradient was induced in one of the branches of the system (mixing channel) by applying external electric field and generating electroosmotic flow in the two other branches of the system. The flow field and transferred mass into the mixing channel can be regulated by controlling the applied voltage of the system. In order to prepare more homogenous mixture solution, some obstacles were added to the mixing channel to induce perturbation in the flow field and enhance the mixing efficiency of the system. Numerical simulations were performed to show the correctness of the proposed mixing strategy and to investigate the influences of the applied voltage on the mixing efficiency and induced pressure flow in the mixing channel. A proposed design can be used as a guideline to control and enhance mixing efficiency, and consequently functionality, of different microfluidic devices.

We present the combination of a state control and shape design approachesfor the optimization of micro-fluidic channels used for sample extraction andseparation of chemical species existing in a buffer solution.The aim is to improve the extraction and identification capacities of electroosmotic micro-fluidic devices by avoiding dispersion of the extracted advected band.