Real-Time Non-Faradaic Potentiodynamic Impedance Sensing Using Screen-Printed Carbon Electrodes

Electrochemical impedance spectroscopy (EIS) is a suitable analytical technique to detect interfacial phenomena and analyte binding at electrode surfaces. In contrast to metallic electrodes, carbon-based electrodes are more suited due to the low cost and the availability of more versatile methods for chemical functionalization. For (bio) sensing, often the Faradaic version of EIS in a three-electrode configuration is used, where a redox-active species is used as a marker. In order to avoid interference due to the redox-active marker with the interfacial interaction, we focus here on the use of non-Faradaic EIS in the absence of any added markers. First, we utilize the sedimentation of silica beads as a model system, which reduces the complexity of the interaction simplifying the interpretation of the measured signals. Moreover, we introduce two improvements. First, impedance measurements are performed in a three-electrode configuration with applied potential as an additional variable, which serves as a handle to optimize the sensitivity. Secondly, we present a time-differential strategy to detect subtle changes and demonstrate that we can consistently follow the sedimentation of beads using the non-Faradaic impedance as a function of the applied potential. Finally, we show a proof-of-principle demonstration for the biosensing of cell attachment on the electrodes in real-time using the proposed technique.