Impedance Characterization of the Degradation of Insulating Layer Patterned on Interdigitated Microelectrode

Abstract

Life-time and functionality of planar microelectrode-based devices are determined by not only the corrosion-resistance of the electrode, but also the durability of the insulation layer coated on the transmission lines. Degradation of the insulating layer exposed to a humid environment or solution may cause leakage current or signal loss, and a decrease in measurement sensitivity. In this study, degradation of SU-8, an epoxy-based negative photoresist and insulating material, patterned on Au interdigitated microelectrode (IDE) for long-term (>30 days) immersion in an electrolyte at 37 °C was investigated by electrical impedance spectroscopy and theoretical equivalent circuit modeling. From the experiment and simulation results, it was found that the degradation level of the insulating layer of the IDE electrode can be characterized by monitoring the resistance of the insulating layer among the circuit parameters of the designed equivalent circuit modeling.

Annealing Effects of Parylene-Caulked Polydimethylsiloxane as a Substrate of Electrodes

“…In addition, the electrode impedance based on both substrates converged to similar values after 200 days. The measured impedance magnitudes were comparable with those of other surface-type electrodes [37,38,39,40]. Annealing turned out to contribute to the increase in the electrode impedance without a reduction of the electrode areas.…”