Application of Electrochemical Impedance Spectroscopy for Implants with Sputtered Iridium Oxide Coatings

The iridium oxide coating reportedly has a catalytic response for the decomposition of hydrogen peroxide, which could have utility for biological effects. Processing, structure, and characteristics of iridium oxide (IrOx) have been published in journals along with patterns for medical implants. Electrochemical impedance spectroscopy (EIS) is a useful tool for various IrOx measurements. It is an electrochemical method in which an alternating current is applied to IrOx thin film which was coated on stainless steel substrate, and the impedance response is measured in a phosphate buffered Saline solution at room temperature. A special parallel model was created for impedance data fitting.

The experiment results clearly show that spectrum is sensitive to the degree of surface area and oxide property. The spectra change in a manner that is consistent with the electrical circuit analogue derived for sputtered iridium oxide film. The double layer capacitance from EIS results is proportional to the scanning electron microscopy images and the root mean square data of atomic force microscopy surface roughness, the oxide capacitance correlated with oxygen rate in the sputtering and Auger electron spectroscopy depth-profiles, and the total capacitance matched with cyclic voltammetry capacitance data.

A higher oxygen rate in sputtering produces more or higher iridium oxide, which creates a supercapacitor with a high capacitance for charge transfer as indicated by electrochemical impedance spectroscopy. The IrOx supercapacitor promotes a better decomposition reaction of hydrogen peroxide to water and oxygen, and this effect may have utility in biomedical applications.