In-Vitro and In-Vivo Longevity Evaluation of Free-Floating Intracortical Silicon-Stiffened Neural Probes

This conference paper presents the latest results of the in-vitro and in-vivo longevity evaluation of silicon-stiffened neural probes designed for a free-floating implantation into the cortex to reduce the foreign body response and thus enable a chronic application. The polyimide-based electrical insulation of the flexible gold conductive paths revealed a long-term stability of up to 10 months immersed in Ringer’s solution at 37°C using the current microfabrication process. In-vivo impedance measurement results show a stabilization of the electrode impedance after approximately 3 weeks post implantation. Recording of spontaneous neural activity in rat visual cortex using chronically implanted probes was done to evaluate the long-term signal quality. Spikes were observable on many channels after at least 55 days post implantation. These results indicate the applicability of the presented probes for chronic neural interfacing.