Fig. 4: Graphene-based transparent electrode array for simultaneous electrical and optical modalities.

a Schematic of a graphene-based transparent neural interface. The honeycomb-lattice structure of graphene maximizes electrode transparency. b Calcium transient images under a graphene-based transparent electrode with 488 nm excitation wavelength. Six cells are numbered in the region of interest. Scale bar: 50 µm. c Correlation between electrophysiological signals reflecting manually induced interictal-like effects (top) and simultaneous ΔF/F0 curves for numbered cells in panel b (bottom). All data from panels b and c are observed simultaneously. d Fluorescence image of a GCaMP6f mice cortex under a transparent graphene electrocorticography (ECoG) array. Scale bar: 200 µm. e Spatiotemporal fluorescence recordings with various electrical stimulation amplitudes. f Plot of intensity changes versus the lateral position. The greatest intensity changes were detected at the stimuli point (between 1.5 and 2 mm). The lateral position axis corresponds to the horizontal red line in panel e. g Bright optical image of the transparent graphene electrode array on the brain surface. Scale bar: 500 µm. h Two-photon imaging at a depth of 1,200 µm under photoelectric artifact minimized graphene electrode. Scale bar: 100 µm. i Crosstalk-free detection of two-photon imaging and electrophysiological recording, according to simultaneous optogenetic stimulation. Panel a, b, and c adapted from ref. ²⁴, Springer Nature Limited. Panel d, e, and f adapted with permission from ref. ¹⁵, American Chemical Society. Panel g, h, and i adapted from ref. ¹⁰⁹, Springer Nature Limited.