Neural electrode degradation from continuous electrical stimulation: comparison of sputtered and activated iridium oxide.
The performance of neural electrodes in physiological fluid, especially in chronic use, is critical for the success of functional electrical stimulation devices. Tips of the Utah electrode arrays (UEAs) were coated with sputtered iridium oxide film (SIROF) and activated iridium oxide film (AIROF) to study the degradation during charge injection consistent with functional electrical stimulation (FES). The arrays were subjected to continuous biphasic, cathodal first, charge balanced (with equal cathodal and anodal pulse widths) current pulses for 7h (>1 million pulses) at a frequency of 50 Hz. The amplitude and width of the current pulses were varied to determine the damage threshold of the coatings. Degradation was characterized by scanning electron microscopy, inductively coupled plasma mass spectrometry, electrochemical impedance spectroscopy and cyclic voltammetry. The injected charge and charge density per phase were found to play synergistic role in damaging the electrodes. The damage threshold for SIROF coated electrode tips of the UEA was between 60 nC with a charge density of 1.9 mC/cm(2) per phase and 80 nC with a charge density of 1.0 mC/cm(2) per phase. While for AIROF coated electrode tips, the threshold was between 40 nC with a charge density of 0.9 mC/cm(2) per phase and 50 nC with a charge density of 0.5 mC/cm(2) per phase. Compared to AIROF, SIROF showed higher damage threshold and therefore is highly recommended to be used as a stimulation material.
Negi
Sandeep
S
Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112, USA. s.negi@utah.edu
Bhandari
Rajmohan
R
Rieth
Loren
L
Van Wagenen
Rick
R
Solzbacher
Florian
F
D000818:Animals; D016477:Artifacts; D001826:Body Fluids / Q000502:physiology; D004558:Electric Stimulation / Q000295:instrumentation / Q000379:methods; D004566:Electrodes / Q000592:standards; D004567:Electrodes, Implanted / Q000592:standards; D004581:Electronics / Q000295:instrumentation* / Q000379:methods; D004594:Electrophysiology / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007495:Iridium / Q000737:chemistry*; D013058:Mass Spectrometry; D008855:Microscopy, Electron, Scanning; D009482:Neurophysiology / Q000295:instrumentation* / Q000379:methods; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation; D013057:Spectrum Analysis
C044458:iridium oxide; D007495:Iridium