Sensing and detecting microparticles require a bulk fluid motion towards the sensing element in order to get a desirable response from the sensing element. Especially for low-concentrated fluid suspension response time is very long. So both, for detection and sensing mechanism if the fluid flow is guided at a reasonable speed and at a low voltage and relatively low frequency which is suitable for bio-particles; the sensing mechanism can be enhanced largely. But sometimes, it is required to re-accumulate or recombine the fluid bulk to ensure a proper sensing and detection process. In this analysis, the fluid flow was disbursed away from a particular location in order to re-accumulate the fluid particles just by changing frequency. Previously parallel plate configuration was used to concentrate particle, but this is for the first time a V-shaped electrode pattern used to guide the bulk flow for concentration purposes. The V-shaped electrode set-up was made by following an unconventional way using a sputtering machine which was cheaper than the conventional Photolithography method. AC- Electroosmosis from planar electrodes is a strong mechanism for creating micro-flows from several hundred microns away from the electrode surface. The mechanism for the AC Electroosmotic fluid flow is based on Capacitive charging which causes due to the generation of counter-ions at the electrode-electrolyte interface and Faradaic charging which is generated by the accumulation of co-ions. These two different methods are responsible for a converging and diverging surface flow of the fluid particles. At a lower voltage, the capacitive charging method plays a significant role and most of the applied voltage drops occur at the electrical double layer but up to a certain voltage level, the Faradaic charging method takes over and starts dominating. The induced flow velocity by both of these methods has a different relationship with the applied voltage. In this experiment, Electrical Impedance Spectroscopy (EIS) was used to determine the suitable frequency range for the application & 1 V~rms~ was used initially which is a very low voltage. An equivalent circuit for the setup was analyzed as the Faradaic charging has dependency on the geometry of the setup. Finally, an analysis was made on this setup using conductive fluid to observe the AC Electrothermal (ACET) effect. In our experiment, the goal was to get an optimum velocity for concentration at low voltage and low frequency also to observe the change in direction of the fluid flow in order to find a way to recombine and re-accumulate with the rest of the flow.


Micro Flow Direction Analysis Using Gold Sputtered Planar V-Shaped Electrode Pattern

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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