Flexible nerve stimulation electrode with iridium oxide sputtered on liquid crystal polymer

Area of Science:

• Materials Science
• Biomedical Engineering
• Electrochemistry

Background:

• Flexible electrode substrates require low moisture absorption and high charge injection.
• Sputtered iridium oxide films offer superior charge injection and substrate adhesion.
• Liquid crystal polymers (LCPs) exhibit minimal water absorption, making them ideal flexible substrates.

Purpose of the Study:

• To evaluate the performance and durability of sputtered iridium oxide films on LCP substrates for neural electrodes.
• To assess the charge injection capabilities and stability of this electrode-substrate combination under accelerated aging conditions.

Main Methods:

• Sputtered iridium oxide films were fabricated on LCP substrates.
• Electrode samples were subjected to accelerated aging (700 h at 67°C in bicarbonate buffer saline) using specific biphasic current waveforms (50 Hz, 100 µs duration, 10 mA).
• Scanning electron microscopy and electrochemical analysis were performed to assess material loss, delamination, charge injection limits, and cathodic charge storage capacity.

Main Results:

• Scanning electron microscopy revealed no delamination and minimal material loss (~1%) after aging.
• The charge injection limit was measured at 4.6 ± 1.0 mC/cm², and cathodic charge storage capacity was 31.5 ± 6.6 mC/cm².
• Electrochemical analysis indicated charge imbalance due to oxygen reduction, but overall stability was high.

Conclusions:

• Sputtered iridium oxide films on LCP substrates demonstrate excellent mechanical stability and electrochemical performance.
• The combination is flexible, chemically inert, and biocompatible, suitable for neural electrode applications.
• This electrode-substrate system presents a viable and potentially superior method for flexible nerve electrode fabrication.