Design of a micro-interdigitated electrode for impedance measurement performance in a biochemical assay

Abstract

The performance of interdigitated electrodes for impedance measurements is dependent upon the geometric design of the electrode pattern and can be significantly impacted by manufactured variability or defects. For processes which rely on precise electrode performance, such as the biochemical assay in the Daktari CD4 diagnostic system, it is necessary to minimize variation through robust design and quality control. Interdigitated electrode design was investigated to identify design strategies which maximize electrode sensitivity and minimize performance variability in produced parts, while potentially reducing the complexity of quality testing. Several configurations were developed to address these goals by increasing the sensing region for a specified electrode area and creating designs which can be more easily manufactured with low variability. Design modifications included alterations to interdigitated finger orientation, finger geometry, and gap width. Test findings indicate that optimal designs contain narrow gap widths with electrode fingers parallel to the longest dimension of the electrode. These benefits may be further enhanced by replacing straight finger edges with geometrical features, such as scalloped edges. The design changes identified can be used to improve interdigitated electrode performance for an array of applications and reduce performance variability caused by variation in the manufacturing process.