PROJECT ABSTRACT Electroencephalography (EEG) is an essential clinical diagnostic and research tool in neurology, neurorehabilitation, cognitive, and behavioral neuroscience. However, in more than 100 years of EEG research, the fundamental EEG technology has remained primitive and game-changing technological innovations have been few and far between. Most current EEG systems rely on gelled silver/silver- chloride or metal electrodes affixed on the scalp with conductive gels or pastes. These devices suffer from the large size of the electrodes, cost, risk of corrosion, preparation, and cleaning. In addition, gels and pastes are necessary to achieve adequate impedance and signal quality, but can be irritating to the skin and dry out over time. Dry (i.e., gel-free) EEG systems can bypass some of the issues of these wet EEG devices, but are still critically limited in terms of subject comfort and signal quality. Finally, MRI-compatible EEG systems for multimodal brain mapping are often highly specialized and expensive. Here, we propose to validate a fully novel, dry EEG system based on MXene materials. MXenes offer high biocompatibility, stability, conductivity, flexibility and low electrochemical impedance. In addition, they can be processed at a low cost, easily integrated into functional neural devices with a variety of geometries and shapes, record brain electrical activity with high fidelity without the need for gels or pastes, and interact weakly with magnetic fields. These properties make MXene ideal to serve as enabling material for the next-generation EEG technologies. In this proposal, we will build on promising pilot data to scale-up and optimize the fabrication and design of MXene EEG electrodes. Specifically, we will aim to outperform the electrodes used in our pilot studies while maintaining fast, cost-effective, and reliable fabrication. Then, we will validate the performance of the best performing MXene electrodes on well-established behavioral tasks associated with readily identifiable EEG spectral characteristics. Finally, we will examine the MRI compatibility of a customized multichannel MXene EEG system for simultaneous EEG/MRI mapping using quantitative and clinician ratings of signal quality, an essential step to propel its widespread adoption in brain research and clinical contexts. By completing this project, we expect to move the field forward by generating a novel dry EEG technology with superior resolution, signal fidelity, and usability compared to current tools. These advantages could pave the way for fundamental innovations in a number of domains including clinical neurology, rehabilitation, and cognitive neuroscience.