Layer-by-layer nanoassembly of iridium oxide/platinum-black for low impedance, high charge injecting microelectrode applications

We report an electrode device with a low impedance and high charge injecting characteristics for a powerful application to micro/nano-scale electrophysiological measurements of neuron/cells. Due to the small effective electrode area, conventional microelectrodes exhibit high interfacial electrode impedance (~10 MΩ at 1 kHz) and low charge injection characteristics, making the targeted cells impossible to record/stimulate. To overcome these limitations, we propose enhanced surface-area of an electrode with a low impedance material, based on layer-by-layer assembled iridium oxide (IrOx)/platinum-black (Pt-black) with nano-scale roughness. The assembled nanorough-IrOx/Pt-black electrode exhibits 2 times lower impedance and 2.4 times larger injection delivery capacity (Q_CDC) compared to a planer-IrOx electrode with the same size. Additionally, we fabricated nanorough-Ir/Pt-black tipped microprobes and demonstrated in saline, while improved stimulating currents were observed.