Optimization of sputtered iridium oxide microelectrodes for long-term intracortical stimulation

Area of Science:

• Biomaterials Engineering
• Neuroscience
• Materials Science

Background:

• Clinical neural prostheses require electrodes with excellent stimulation properties and long-term stability.
• Iridium oxide is a promising material, but its performance depends heavily on fabrication parameters.

Purpose of the Study:

• To investigate the fabrication of sputtered iridium oxide films (SIROFs).
• To optimize SIROF fabrication for enhanced electrochemical properties and stability for intracortical stimulation.

Main Methods:

• Fabrication of SIROFs with varying oxygen flow, sputtering power, and sputtering time.
• Electrochemical characterization using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).
• Pulsing experiments and in vivo stability testing in non-human primates.

Main Results:

• Optimal SIROF fabrication achieved at 5% oxygen flow, 80 W, and 7 minutes, yielding a 660 nm film.
• Electrodes exhibited low impedance (4.8 kΩ at 1 kHz) and high charge injection capacity (2.3 mC/cm²).
• Stable performance demonstrated over 276 million pulses and three months in vivo.

Conclusions:

• Optimized SIROFs possess superior surface structure and electrochemical properties.
• The material demonstrates exceptional robustness and long-term stability for chronic clinical applications.
• SIROFs are a viable material for efficient and safe intracortical stimulation in neural prostheses.