Yunxia Jin1,Chne-Wuen Tsai2,1,Sippanat Achavananthadith2,Dat T. Nguyen3,Jerald Yoo2,1,Yuxin Liu1,John S. Ho1,2
National University of Singapore1,Department of Electrical and Computer Engineering, National University of Singapore2,Integrative Sciences and Engineering Programme, National University of Singapore Graduate School3
Yunxia Jin1,Chne-Wuen Tsai2,1,Sippanat Achavananthadith2,Dat T. Nguyen3,Jerald Yoo2,1,Yuxin Liu1,John S. Ho1,2
National University of Singapore1,Department of Electrical and Computer Engineering, National University of Singapore2,Integrative Sciences and Engineering Programme, National University of Singapore Graduate School3
Single-unit electrophysiological recording at electrode density comparable to neural density is critical to interrogate the function of the brain and the study of neurological diseases. In addition, three-dimensional triangulation of neuron location by spatially oversampled multiple single-unit recording requires closely-packed ultrahigh-density electrodes. However, the electrode spatial density is currently limited by high electrochemical impedance and availability of interfacing materials and fabrication method. Here, we propose and demonstrate a graphene-edge neuroelectronics with a density of more than 2000 electrodes/mm<sup>2</sup>, exceeding the neural density in the brain. By exposing nanotextured graphene edges on the cross-section of the probe, each channel of dimensions less than 12 μm achieves an impedance of less than 1 MΩ and a charge injection capacity of more than 1 mC/cm<sup>2</sup>. Notably, the probe records neural activity with high action potential amplitudes approaching 1 mV and allows reliable detection of multiple single-units in cortical areas. We further show that chronically implanted probes exhibited stable electrochemical impedance, high signal-to-noise ratio of more than 20 dB, and single-unit tracking capabilities over 3 months. This work paves the way for ultrahigh-density chronic neural recording for closely-packed neurons in the brain.