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Microelectrode arrays (MEAs) have enabled investigation of cellular networks at sub-millisecond temporal resolution. However, current MEAs are limited by the large electrode footprint since reducing the electrode’s geometric area to sub-cellular dimensions leads to a significant increase in impedance thus affecting its recording capabilities. We report a breakthrough ultra-microelectrodes platform by leveraging the outstanding surface-to-volume ratio of nanowire-templated out-of-plane synthesized three-dimensional fuzzy graphene (NT-3DFG). The enormous surface area of NT-3DFG leads to 140-fold reduction in electrode impedance compared to bare Au microelectrodes, thus enabling scaling down the geometric size by 625-fold to ca. 2 µm × 2 µm. The out-of-plane morphology of NT-3DFG leads to a tight seal with the cell membrane thus enabling recording of electrical signals with high signal-to-noise ratio (SNR) of > 6. This work highlights the possibility to push the limits of the conventional MEA technology to enable electrophysiological investigation at sub-cellular level without the need of any surface coatings. This presented approach would greatly impact our basic understanding of signal transduction within a single cell as well as complex cellular assemblies.
T. C.-K. acknowledges funding support from the National Science Foundation under Award No. CBET1552833 and the Office of Naval Research under Award No. N000141712368. J. B. and A. W. F. acknowledge financial support from the Dowd Fellowship from the College of Engineering at Carnegie Mellon University. L. M. and F. S. acknowledge Valentina Mollo for ssthe preparation of SEM/FIB samples. We also acknowledge support from the Department of Materials Science and Engineering Materials Characterization Facility (MCF-677785).