Fabrication of comb interdigitated electrodes array (IDA) for a microbead-based electrochemical assay system

This research is directed towards developing a more sensitive and rapid electrochemical sensor for enzyme labeled immunoassays by coupling redox cycling at interdigitated electrode arrays (IDA) with the enzyme label β-galactosidase. Coplanar and comb IDA electrodes with a 2.4 μm gap were fabricated and their redox cycling currents were measured. ANSYS was used to model steady state currents for electrodes with different geometries. Comb IDA electrodes enhanced the signal about three times more than the coplanar IDAs, which agreed with the results of the simulation. Magnetic microbead-based enzyme assay, as a typical example of biochemical detection, was done using the comb and coplanar IDAs. The enzymes could be placed close to the sensing electrodes (∼10 μm for the comb IDAs) and detection took less than 1 min with a limit of detection of 70 amol of β-galactosidase. We conclude that faster and more sensitive assays can be achieved with the comb IDA.