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In situ stability monitoring of platinum thin-film electrodes for neural interfaces in the presence of proteins

The long-term stability of platinum electrodes is a key factor that determines the life-time of biomedical devices, such as implanted neural interfaces like brain stimulation or recording electrodes, cochlear implants, and biosensors. The downsizing of such devices relies on the usage of microfabricated thin-film electrodes. In order to determine and investigate the causal degradation processes for platinum electrodes, it is essential to use potential-controlled experiments, which allow selectable polarization of the electrode without exceeding the water stability window boundaries. Therefore, the surface processes and redox reactions occurring at the electrode are known at all times. In this study, we present the continuous in situ monitoring of platinum-based thin-film electrodes along their complete life cycle in neutral pH with and without the presence of proteins. The usage of chronoamperometry for electrode aging, monitoring of surface processes and the tracking of analyte redox processes, together with cyclic voltammetry to determine the complete amount of surface charge, allows a reliable quantification of fundamental degradation processes. We found that platinum dissolution is primarily driven by the formation and removal of Pt oxide. Despite the significantly lowered charge transfer, the presence of proteins did not prevent material loss or increase electrode lifetime. These results should be considered when interpreting results from current-controlled methods as typically used for neural interfaces. Clinical Relevance— All clinically relevant applications of microelectrodes, ranging from cell culture over diagnostics to in vivo use, involve the presence of proteins. Detailed and fundamental insight into electrode stability in the presence of proteins is therefore essential for successful clinical translation of neural interface technologies.