Charge Injection Enhancement Comparisons of Iridium Oxide Microelectrodes In Vitro and In Vivo Using a Portable...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Materials Science

Background:

• Microelectrodes are crucial for neural tissue stimulation.
• Delivering higher charges safely is essential for effective neurostimulation.
• Anodic bias potential is a known method for charge enhancement.

Purpose of the Study:

• To investigate charge enhancement using anodic bias potential.
• To evaluate this technique in both in vitro and in vivo settings.
• To validate a custom-designed portable neurostimulator for wireless in vivo stimulation.

Main Methods:

• Used a custom microelectrode probe with activated iridium oxide sites (2000 μm² GSAs).
• Measured voltage transients in saline (in vitro) and rat primary motor cortex (in vivo).
• Applied constant current stimulation with and without 500 mV anodic bias potential.

Main Results:

• Anodic bias potential increased charge injection capacity in both in vitro and in vivo conditions.
• In vitro: capacity rose from 10 nC/phase to 32 nC/phase (200 μs pulse width).
• In vivo: capacity increased from 2 nC/phase to 8 nC/phase.

Conclusions:

• Anodic bias potential significantly enhances charge injection capacity of microelectrodes.
• The order of charge injection capacity (lowest to highest) was: in vivo without bias, in vivo with bias, in vitro without bias, in vitro with bias.
• The portable neurostimulator was successfully validated for wireless in vivo neurostimulation.