Robustness and repeatability of interdigitated electrodes on a substrate tested in an aqueous environment

Abstract

Interdigitated electrodes are currently being used as sensing components in microfluidic lab-on-a-chip devices. The Daktari Diagnostics system uses these electrodes to measure the change in impedance of a fluid in an assay chamber. In order to improve quality assurance, a new testing method was developed and validated to characterize the sources of potential defects in the electrodes. In the new test, the electrodes are used to measure the impedance when placed in solutions of different known conductivities. The data was used to estimate the linear relationship between the inverse of the measured impedance to the solution conductivities. The repeatability tests found an average slope of 1.438x10-5 cm/characteristic length with a standard deviation of 8.52x10 -8 cm/characteristic length. It was found that the number of defective fingers or bending the electrodes significantly changes the electrode performance with a 95% confidence interval.