Advanced Flexible Neural Probe Design Using One-Step Chemical Vapor Deposition of Iridium Dioxide Nanoparticles for Neural System Stimulation

Various neural probes that can provide highly precise stimulation and prevent cellular damage and interference have been used to stimulate neural systems such as the brain and spine. These probes are designed to be micron-sized; therefore, they are mechanically fragile and have high impedances. Mechanical fragility can be overcome using flexible probes, which are suitable for long-term applications. However, the impedance of these probes, which is the most important property to be considered for electrical stimulation, is being lowered via diverse methods that have several limitations. In this study, iridium dioxide, which is often used to fabricate electrodes for oxidation-reduction reactions due to its high pseudo capacitance, was coated via a one-step chemical vapor deposition method onto the copper-gold electrodes of a flexible neural probe to decrease the overall impedance of the probe. Unlike other methods, this approach is remarkably simple in its process, requires minimal time, and does not compromise the performance of the flexible neural probe with superior electrochemical properties. The impedance of the probe at 1 kHz decreased from approximately 500 kΩ before the coating to 5 kΩ after the coating. Additionally, in vivo tests on mice revealed that an effective stimulation shape was modulated owing to the distinct surface morphology of the probe. These results indicate that the flexible neural probes coated with iridium dioxide can be used for stimulating neural systems.