Application of Electrochemical Impedance Spectroscopy (EIS) to Electrokinetic Characterization of Planar Microfluidic Substrates

Electrokinetic phenomena play an important role in characterization of microfluidic and colloidal substrates. In terms of consolidated substrates, the measurement of streaming potential or streaming current can be used to infer the influence of liquid parameters on the zeta potential of the substrates. The classic Helmholtz-Smoluchowski equation is generally used to correlate the zeta potential to the streaming potential/current. In the current work, different sets of experiments are performed in order to investigate zeta potential’s dependency on ion concentration and pH value for poly (methyl methacrylate) (PMMA) and borosilicate glass.  Non-linear (electrochemical impedance spectroscopy) and linear (DC voltage/current) resistance measurements of a streaming potential setup are carried out under experimental conditions. We find that the resistance of much diluted electrolytes show considerable deviations from theory which cannot be explained by the phenomenon of surface conductivity. The results of the impedance measurements and the streaming current can be used to derive correlations for the correction of the classic streaming potential theory.