Characterization of non-faradaic label free impedimetric electrochemical sensor

Abstract

The developments in microfluidics and BioMEMS have led to miniaturized high-performance droplet-based sensors. These sensors must be reliable, simple, fastresponding and cost-effective to be used in biomedical applications. In this work, the non-faradaic electrochemical impedimetric approach is studied to measure different salt concentrations and different pH values. Label-free measurements are done to characterize electrical double layer capacitance (Cedl) and solution resistivity (Rs). For this purpose, gold interdigitated electrode (AuIDE) is fabricated on a glass wafer. Three different salt (LiCl, KCl and NaCl) solutions in different molarities between 0,001Mto0,1MandwithdifferentpHvalues(pHrangebetween2.0to11.50atconstant conductivity) are prepared. Impedance measurements are taken from an AuIDE at a frequency range of 20 Hz to 10 MHz, with an amplitude of 10 mV using an Impedance Analyzer (E4990A) to extract the values of Cedl and Rs. The data is interpreted according to both Cedl and Rs values and Nyquist plots. Results for both salt and pH solutions exhibit that as solution molarity increases, the Cedl values also increases and each solution shows different patterns on Nyquist plots. This study can lead to label free measurement of analyte type, concentration and pH values upon data processing of multiple reference and analyte measurements.|Keywords : Electrical double layer, impedimetric sensor, salt concentration and pH characterization, Nyquist plots, data processing.