Conducting Polymers for Neurostimulation

Microelectrodes for high resolution neurostimulation enable therapies and treatments for a variety of neurological disorders and diseases. To enhance the electrochemical interface and ensure sufficient charge injection capabilities, microelectrodes are commonly coated with organic mixed ionic-electronic conductors (OMIECs) that provide a volumetric interaction with the electrolyte. Despite the accelerated development of a large variety of OMIECs, PEDOT:PSS is almost exclusively used as an electrode coating material and is favored for its commercial availability, electrical conductivity, stability and processability. Other OMIECs with different electronic-ionic transport and coupling properties have been characterized and benchmarked for organic electrochemical transistors by determining the product of the electronic mobility and the volumetric charge storage capacitance (μC*), however, remain largely unexplored in the context of neurostimulation.<br/><br/>In this work, we investigated various OMIECs for neurostimulation applications. The materials are examined with electrochemical methods and pulse experiments to determine typical performance parameters such as the electrode impedance, charge injection limit and stability. Furthermore, the observed performance parameters are linked to the OMIEC specific transport and electronic-ionic coupling properties. The results reveal which OMIEC properties are crucial for optimal performance of microelectrodes and provide guidelines that aid the development of OMIECs for electrical stimulation applications.