AC electrokinetic flow is promising in designing microfluidic chips for manipulation of biological and chemical samples toward clinical diagnostics. Four pieces of electrodes are optimized to enhance mixing effect inside a straight microchannel. In this research, the mixing dependency on the ionic strength of solutions is investigated. AC electroosmotic secondary flow is responsible for the mixing at low ionic strength (σ < 5 mS m–1), whereas AC electrothermal secondary flow is proposed to mix high conductive mediums (σ > 5 mS m–1). The electrode-electrolyte impedance analysis is employed to facilitate the in-situation mixing process by choosing appropriate electrical excitation parameters for the electrodes.
