Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112, USA.
J Neurosci Methods. 2010 Jan 30;186(1):8-17. doi: 10.1016/j.jneumeth.2009.10.016. Epub 2009 Oct 28.
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.
神经电极在生理液中的性能，尤其是在慢性使用条件下的性能，对于功能性电刺激设备的成功至关重要。犹他州电极阵列（UEA）的尖端涂有溅射氧化铱膜（SIROF）和活性氧化铱膜（AIROF），以研究与功能性电刺激（FES）一致的电荷注入过程中的降解情况。这些电极阵列接受连续双相、阴极首先、电荷平衡（具有相等的阴极和阳极脉冲宽度）电流脉冲，频率为 50 Hz，持续 7 小时（超过 100 万次脉冲）。改变电流脉冲的幅度和宽度，以确定涂层的损伤阈值。通过扫描电子显微镜、电感耦合等离子体质谱、电化学阻抗谱和循环伏安法来表征降解。发现注入的电荷量和每相电荷量密度在损坏电极方面起着协同作用。SIROF 涂层 UEA 电极尖端的损伤阈值在每相电荷量密度为 1.9 mC/cm(2)时为 60 nC，在每相电荷量密度为 1.0 mC/cm(2)时为 80 nC。而对于 AIROF 涂层电极尖端，阈值在每相电荷量密度为 0.9 mC/cm(2)时为 40 nC，在每相电荷量密度为 0.5 mC/cm(2)时为 50 nC。与 AIROF 相比，SIROF 显示出更高的损伤阈值，因此强烈推荐将其用作刺激材料。
