Numerical simulation of electrokinetic focusing in microfluidic chips

In this paper, we adopt the Nernst-Planck equation and the full Navier-Stokes equation in the modeling of electro-osmotic flow in microfluidic chips. A voltage control model is proposed, which achieves electrokinetic focusing in a pre-focused cross injection system and which allows the volume of the sample to be controlled. In addition to the traditional cross system, we also present a design for a novel pre-focused 1 x 3 (i.e. one sample inlet port and three outlet ports) injection system, which is capable of continuous sample switching and injection for bio-analytical applications. Using the proposed injection system, the sample may be electrokinetically pre-focused and then guided into the required outlet port by suitable manipulations of the applied voltage. The unique microfluidic chip presented within this paper has an exciting potential for use in high-throughput chemical analysis, fast sample mixing and many other applications in the field of micro-total-analysis systems.