On-chip Mixing, Pumping and Concentrating Effects by Using AC Electrothermal Flow

Background: Microfluidic manipulation (including: pumping, mixing and concentrating effects) is highly challengeable for bioengineering and on-chip analysis applications such as point-of-care immune-detection systems. In this research we propose a configurable electrode structure to form various manipulation effects including pumping, mixing and concentrating processes by applying an Alternate Current (AC) electrokinetically-driven flow. Methods: By applying an inhomogeneous electric field causes temperature rise accompanied by temperature gradients generation inside the microchannel. As a result, an AC electrothermal flow generates inside the channel, which is efficient to generate mixing, pumping and concentrating effects. Results: The proposed system is studied numerically by Finite-Element-Method, Based on the results, a) bulk fluid velocity of 100 μm/s is achieved by exciting the electrodes in pumping mode, b) complete mixing efficiency is observed in mixing mode, c) for antibody-antigen binding process (concentrating mode), the surface reaction increases by the factor of 9 after 5 seconds of sample loading. Results reveal that the system is highly efficient for bio-fluid mediums. Conclusion: AC electrothermal fluid manipulation process was investigated numerically inside a microchannel for biological buffers. Back and forth fluid motions, clockwise/counter-clockwise rotational vortexes and also antibody-antigen linking enhancement were achieved by engineering the specific electrode patterns. The manipulation efficiency improves by increasing both the amplitude of electric potential and the ionic strength of biofluid. As a result, our proposed configurable device is of interest for onchip immunoassays and point-of-care devices.