Nanostructured porous platinum electrodes for the development of low-cost fully implantable cortical electrical stimulator

A nano-structured porous platinum (Pt-p) electrode is developed in order to facilitate a low-cost, fully implantable cortical electrical stimulation (CES) device for animal experiments. The Pt-p electrode is made by electrochemical surface modification, which results in a nano-structured porous top layer (∼1.5 μm thick) revealed by scanning electron microscopy (SEM). A roughness factor (R) of 35.9 indicated by cyclic voltammetry (CV) implies expanded interface area up to 35.9 times. The impedance of the Pt-p microelectrode decreased by 77% at 1 kHz measured using electrochemical impedance spectroscopy (EIS). Moreover, the voltage of the electrode under monopolar stimulation in response to stimuli has been reduced by approximately one third, which favors lower compliance voltages and power saving for the implant. Importantly, the Pt-p microelectrode demonstrates excellent mechanical stability and electrochemical stability during ultrasonic bath and CV in vitro. Finally, the implant has been implanted in the cortex of rats for CES study up to 16 days. There were no significant statistical differences in neuronal survival data between CES group and non-stimulation group, suggesting satisfied neuron viability under long-term electrical stimulation with Pt-p electrodes. This shows that the Pt-p electrode is safe and effective in the application as a low cost CES implant.