EAGER: Exploiting Superior Electrochemical Characteristics of Scaled PEDOT:PSS Microelectrode Arrays for High Fidelity Electrocorticography

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Abstract Nontechnical: Electrophysiological clinical mapping of brain activity has high spatial resolution and high sensitivity that supersedes other noninvasive techniques such as functional magnetic resonance imaging (fMRI). This clinical procedure is important for a large population of patients with neurological disorders that either do not respond to drugs or have adverse side effects such as in medically intractable epilepsy. It also has promising applications in brain-machine interfaces. The majority of electrophysiological devices utilize noble metals as the contact interface with brain tissue, and these metal electrodes detect ionic currents and potentials by either surface redox reactions or capacitive charge screening. Organic electrodes on the other hand are permeable to ions and allow volumetric redox reactions and capacitive coupling of brain activity. This superior electrochemical performance allows organic electrodes to resolve minute potentials from the brain which has implications for better understanding and treatment of neurological diseases. But their superior characteristics fade with time due to instability of the bonding interface between the organic electrode and the underlying metal pads that carry the signals to the outside world. This project aims at improving the stability of these organic electrodes by developing novel fabrication procedures that can extend their superior performance for several years. Technical: This project combines expertise in electronic materials processing, electrophysiological recording from humans, and data analysis in order to develop new geometries of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate microelectrodes. Device geometries that can result in the lowest electrochemical impedances and highest electrochemical stability will be developed and characterized with accelerated aging experiments in-vitro. Impedance and cyclic current-voltage characterization will be monitored over the course of several weeks while the microelectrodes are immersed in saline solution at high temperatures. Surface and cross-section scanning electron microscopy and atomic force microscopy will be utilized to assess the morphological stability of these microelectrodes and will inform the device fabrication to develop stable interfaces. The research is integrated with an educational plan for students with a central focus on biomedical implant devices as well as on the burgeoning field of neuro-technology. The plan includes extensive education and training programs for undergraduate and graduate students, with an emphasis on minority, female, and other underrepresented groups. If successful, the devices will broadly impact how we understand the brain, diagnose diseased regions of the brain, and advance the development of brain implants potentially opening access to such information to broader societal populations.