Frequency dependence on the accuracy of electrical impedance spectroscopy measurements in microfluidic devices

This communication presents the dependence on frequency of the accuracy of electrical impedance spectroscopy (EIS) measurements in microfluidic devices. For this study, a very simple microfluidic device was used, with a hydrophilic microfluidic channel in which two parallel electrodes were patterned. Glass was the preferred substrate material for the fabrication of this microfluidic device, mainly due to its excellent dielectric properties even at relatively high frequencies. The testing was performed in air, and with DI water, ethanol and solutions of silica beads suspended in ethanol. The results show that the accuracy of the measurement increases with the frequency. The variation of the average of standard deviation error was between 13% at 10 kHz and less than 1% at 100 MHz. This clearly indicates that a high frequency range must be considered for further studies using electrical impedance spectroscopy in microfluidic devices.