PEDOT:PSS coated gold nanopillar microelectrodes for neural interfaces

Improving the neuron-electrode interface has been the focus of research for the last decade. Low impedance, high charge storage capacities and small geometrical surface area are desired for all neuroelectrodes. A common way to improve this interface is to increase the electrochemically active surface area of the electrode by using nanoporous or nanostructured electrode materials. In this paper the fabrication of microelectrodes with very high aspect ratio (AR > 100) gold nanopillars coated with the conducting polymer PEDOT is presented. Gold nanopillars are manufactured using a template based electrodepositioning process. PEDOT is polymerized from a sodium polystyrenesulfonate (NaPSS) dispersion onto planar gold electrodes and gold nanopillar electrodes. The polymer coated electrodes are studied using scanning electron microscopy, atomic force microscopy, impedance spectroscopy and cyclic voltammetry. PEDOT coated Nanopillar electrodes show reduced impedance over the entire frequency range of 1 Hz - 100 kHz. Depending on height the impedance is more than 350 times smaller at 1 kHz compared to planar gold electrode and reveals a capacity more than 1000 times higher in comparison to the planar reference.