Abstract

Electrochemical impedance spectroscopy (EIS) is a rapidly developing technique in microfluidics for characterizing materials and interfaces. By using equivalent circuits as models, it can determine the electrical properties of heterogeneous systems like membranes or electrolytes in a microfluidics chamber. For measuring Impedance spectroscopy, a small amount of perturbing sinusoidal signal was applied to the electrochemical microfluidic cell and measured the resulting current response. Two main ways to visualize EIS are Nyquist and Bode plot. In our research, both of these plots describe the characteristics of the electrochemical system in their ways. In our studies, we analyzed both the Bode plot and Nyquist plot for two different electrodes arrangement named as T shaped electrode (or orthogonal electrode) and V-shaped electrodes. We also compare these electrodes in three different electrolytes DI water (18.72μS/cm), tap water (666.12 μS/cm) and PBS 1× (8235.24 μS/cm) with three different ranges of conductivity to observe their characteristics changes and to compare them. We analyze the capacitive effect or electric double layer (EDL) effect for the electrode and electrolyte interface and how electron transfer kinetics and diffusional characteristics affect the spectra. As Impedance takes into account all factors such as capacitance, resistance or inductance besides the ideal resistor, it can define the characteristics of each different cell or electrode pattern by the spectra. For our microfluidics system, the capacitive systems are traditionally very large especially at the low frequencies because of impedance. The purpose of this research is to find the optimal operating range for different AC electrokinetic mechanism.

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