Assessing polarization of AIROF microelectrodes.
1Biomedical Engineering Department, Illinois Institute of Technology, Chicago, IL 60616, USA.
Summary
Activated Iridium Oxide Film (AIROF) microelectrodes show reduced in vivo performance due to ion depletion. Thicker AIROF films, while offering high charge capacity in vitro, can be detrimental for neural prostheses.
Area of Science:
- Biomedical Engineering
- Materials Science
- Neuroscience
Background:
- Activated Iridium Oxide Film (AIROF) microelectrodes offer high charge-delivery capacity for neural prostheses.
- Safe operation requires limiting electrode polarization within the
Purpose of the Study:
- To refine in vivo polarization limit criteria for AIROF microelectrodes.
- To investigate the cause of a secondary ohmic voltage drop observed in vivo.
Main Methods:
- In vivo experiments with AIROF microelectrodes.
- Analysis of voltage drops and their relation to film properties.
Main Results:
- A secondary ohmic voltage drop, not observed in vitro, was identified in vivo.
- This drop increases with AIROF film thickness.
- Thicker AIROF films showed minimal to detrimental in vivo charge delivery despite high in vitro capacity.
Conclusions:
- Ion depletion within the AIROF pore structure likely causes the in vivo ohmic drop.
- Ionic inaccessibility of the porous iridium oxide layer limits effective charge delivery in vivo.
- Findings impact the design of neural prostheses utilizing AIROF microelectrodes.
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