Theoretical and Experimental Study of High Conductive Fluid and Electric Field Interaction inside a Microchannel

Design of on-Chip fluidic devices such as micromixer, micropump, concentrator and so on are particularly troublesome, due to viscose effects in micro-scale. We have studied both the experimental and theoretical effect of AC electrokinetic mechanism for manipulation of high conductive fluids. Fluid velocity control was numerically studied by FE-Anlysis to solve the electrical, thermal and fluid mechanic multi-physic coupled equations. Based on the studies, the efficiency of ac electrothermal phenomena increases theoretically by increasing the ionic strength of fluid medium. From experimental point of view, the Phosphate Buffered Saline is prepared as carrier fluid with different electrical conductivities and then seeded with 1 mu m sized fluorescent particles to investigate fluid motion inside a microchannel. An array of asymmetric electrode pairs were structured on a silicon substrate to generate non-uniform electric field and induce efficient temperature gradient. As a result, the fluid motion starts to occur from the narrow electrodes towards the wide electrodes. Experimental results confirm that the proposed system is highly efficient for conductive mediums and the efficiency improves by increasing both the applied electric field amplitude and frequency. But, electrochemical reaction and electrode degradation is observed at very high conductive mediums (above 0.7 S/m). The frequency behaviour of working fluid is measured by impedance analyser.