Layer-by-layer assembled nanorough iridium-oxide/platinum-black for low-voltage microscale electrode neurostimulation

Electrical neural stimulating electrodes play an important role in medical applications and improving health/medical conditions. However, size reduction for low-invasive electrodes creates issues with high electrolyte/electrode interfacial impedance and low charge-injection characteristics, which makes it impossible to stimulate neurons/cells. To overcome these limitations, we propose an electrode material for low-voltage microscale electrode neurostimulation that combines the advantages of low impedance of iridium oxide (IrOx) with the enhanced surface area of platinum black (Pt-black). Based on a simple, rapid, low-temperature electroplating process, herein a low impedance and high charge-injection electrode is fabricated by a layer-by-layer assembly of IrOx/Pt-black with nano scale roughness. The assembled nanorough-IrOx/Pt-black electrode has an impedance of 32 Omega cm(2) at 1 kHz and a charge-injection delivery capacity (Q(CDC)) of 46.7 mC cm(-2), which are 0.5 and 2.4 times the values for the same-sized IrOx/flat-Pt electrode, respectively. The stimulation capability of the nanorough-IrOx/Pt-black plated microelectrode is confirmed by in vivo stimulations of the sciatic nerve of a mouse. The threshold voltages of 8-mu m-diameter and 11-mu m-diameter electrodes are 700 mV and 300 mV, respectively. However, increasing the diameter of high Q(CDC) nanorough-IrOx/Pt-black can further reduce the stimulation voltage. Consequently, nanorough-IrOx/Pt-black is applicable to low-voltage microscale electrode neurostimulations for powerful in vivo/in vitro electrophysiological measurements. (C) 2014 Elsevier B.V. All rights reserved.