Zeta potential and Reynolds number correlations for electrolytic solutions in microfluidic immunosensors

Abstract

Efficient designs are critical toward obtaining optimal performances in microfluidic immunosensors. In this manuscript, we report a systematic study to characterize the flow characteristics of KCl solutions of different concentrations in trapezoidal Si microchannels with non-functionalized, silanized and antibody-immobilized surfaces. Streaming potentials and pressure drops were measured, and the respective zeta potentials were calculated from the Helmholtz–Smoluchowski equation. The effects of the type of microchannel surfaces, the concentrations and flow rates of the electrolyte concentrations were investigated. Attempts were made to understand the role of zeta potential on the flow characteristics of the solutions in the functionalized microchannels. To the best of our knowledge, such studies have not been reported in the literature. A highlight of the work is that correlations between the zeta potentials with the Reynolds number were found with ζRe0.5 appearing to be reasonably independent of Re for the cases studied here. The results for the antibody-immobilized surfaces could help in further investigations of the electro-viscous effects with phosphate buffer saline solutions containing antigens through the microfluidic immunosensors. We believe that this work advances the knowledge in the area and could be utilized to design efficient immunosensors.