Iridium Oxide-Electrodeposited Nanoporous Gold Multielectrode Array with Enhanced Stimulus Efficacy

Area of Science:

• Materials Science
• Neuroscience
• Electrochemistry

Background:

• Nanoporous gold (NPG) offers a high surface area for electrode fabrication but has a moderate charge injection limit.
• Improving charge injection is crucial for effective and safe neural stimulation and recording.
• Iridium oxide (IrOx) is a promising material for neural electrode coatings due to its electrochemical properties.

Purpose of the Study:

• To enhance the charge injection limit of NPG-based multielectrode arrays (MEAs).
• To investigate the electrochemical properties of IrOx electrodeposited on NPG.
• To evaluate the performance of the novel IrOx/NPG electrodes in neural tissue.

Main Methods:

• Fabrication of MEAs with electrochemically deposited IrOx on NPG.
• Characterization of charge injection limit, charge storage capacity (CSC), and electrochemical impedance.
• Microscopy (STEM) and elemental analysis (EDX) for structural and compositional analysis.
• In-vitro electrophysiological recordings using rat hippocampal slices.

Main Results:

• IrOx/NPG MEAs achieved a charge injection limit of 2.3 mC cm^-2, exceeding the neural damage threshold.
• The IrOx/NPG electrodes exhibited a low impedance (9.7 ± 0.45 kΩ at 1 kHz) and high CSC (8 mC/cm^-2).
• Electrophysiological tests showed improved neural signal detection (steeper fEPSP amplitude, prolonged wave) with IrOx/NPG compared to NPG MEAs.
• Uniform IrOx deposition on the interconnected NPG structure was confirmed.

Conclusions:

• Electrochemical deposition of IrOx on NPG synergistically enhances electrode performance.
• The developed IrOx/NPG MEAs offer superior charge injection capabilities for neural interfaces.
• These findings suggest potential for improved neural recording and stimulation devices.