Fig. 3: Challenges with the integration of electrophysiological and optical modalities by non-transparent neural interfaces.

a Schematic illustration of challenges from non-transparent electrode array with integration of optical modalities. b Orbital electron energy levels versus the density of each state. c Photoelectric artifact from electrophysiological signals from the brain after 473 nm photo-stimulation with an optical fiber. d The trace of electrophysiological signals from panel c. The photoelectric artifact is presented as the onset of stimulation. e Optical Coherence Tomography (OCT) imaging of a brain with a non-transparent platinum electrode array (left) and a transparent graphene electrode array (right). f An image of blood vessels from the brain cortex labeled with rhodamine-B dextran through the platinum electrode array from the cranial window. g Fluorescence image of blood vessels with a transparent graphene electrode array. h Spatiotemporal electrophysiological heatmap of a corresponding electrode channel upon illumination of the 473 nm laser directly on the surface of the Au film electrode (left), and an Au nanonetwork electrode (right). i Spatially distributed electrophysiological potentials from the optogenetic stimulation. The blue color represents the illumination spot. Panels b, c, and d reprinted with permissions from ref. ¹⁹, Royal Society of Chemistry. Panels e and g reprinted with permissions from ref. ¹⁶, Springer Nature. Panels f and i reprinted with permissions from ref. ⁹⁰, IOP publishing. Panel h reprinted with permissions from ref. ¹⁸, Wiley.