A double-sided fabrication process for intrafascicular parylene C based electrode arrays

Area of Science:

• Biomedical Engineering
• Materials Science
• Neuroscience

Background:

• Single-sided fabrication of parylene C electrode arrays limits integration density.
• Advancements in neural implant technology require higher resolution and biocompatibility.

Purpose of the Study:

• To develop a double-sided fabrication process for intrafascicular electrode arrays.
• To enhance integration density and performance of neural electrodes.
• To create injectable electrodes without additional support layers.

Main Methods:

• Utilized a double-sided process with 25 μm platinum iridium foil sandwiched between 10 μm parylene C layers.
• Employed a picosecond laser (355 nm Nd:YVO4) for electrode fabrication.
• Applied electrochemical deposition of nanostructured platinum to compensate for impedance mismatches and increase surface area.

Main Results:

• Fabricated 40 μm thick electrodes with three 80 μm diameter electrodes per side and a dual-sided ground electrode.
• Achieved electrode impedances in the low kΩ range at 1 kHz after platinum coating.
• Determined a safely injectable charge per pulse of 635.75 μC/cm2 for coated electrodes.

Conclusions:

• The double-sided fabrication process offers a viable alternative to lithographic methods for thin, flexible neural electrode arrays.
• Picosecond laser ablation and platinum nanocoating enhance electrode performance and injectability for neural implants.
• This approach facilitates higher integration density crucial for advanced neural interfaces.