This paper presents an experimental investigation on the DC-biased AC-electrokinetic (ACEK) flow vortex in a rectangular microchannel. This is a new flow phenomenon in AC-electrokinetics and had been successfully utilized for microfluidic mixing as reported in our previous work. The microchannel is aligned parallel to a pair of energized coplanar microelectrodes such that the generated flow vortex is perpendicular to the pressure-driven flowing samples. With the application of a DC bias AC voltage, incipient Faradaic reactions occur above the electrodes and thus producing ions and creating a net dominant flow vortex. Further investigation to understand the generation of the DC-biased ACEK flow was conducted. This is performed by direct visualization of such flow vortex formation from the cross-section of a rectangular microchannel.