Low-Impedance Graphene – PEDOT-PSS Electrodes for Neural Recording and Stimulation in Implantable Medical Devices

Flexible electrode arrays with low impedance are becoming critical to enhance single-neuron sensing with high sensitivity. Such electrodes should be scalable to micron dimensions and yet retain low impedance. The key to accomplish this is to achieve: a) higher effective surface area to obtain high capacitance, b) chemically stable and biocompatible materials with no adverse reactions and toxicity, and c) mechanically compliant structures for minimal scar tissue formation. Nanostructured electrode arrays with emerging materials such as graphene and PEDOT -PSS are projected to meet all these requirements. Graphene - PEDOT-PSS films were transferred onto flexible LCP (liquid crystal polymer) substrates to form neural electrode recording arrays. These electrodes were subsequently integrated with flexible passive wireless neural recording sensors to form low-impedance (<1 Ohms-cm2) neural recording units. Impedance enhancements were simulated and validated with an electrochemical analyzer in a phosphate buffered saline PBS solution. In addition, evoked potentials during pulse stimulation were recorded to show improved signal - noise ratio with low-impedance electrodes.