Fig. 5: Additional transparent materials for simultaneous electrical and optical modalities.

a Carbon nanotube (CNT) transparent electrode array on a stretchable substrate. b Minimized light-induced artifact of a CNT electrode compared with a gold electrode. c Simultaneous electrode recording (top) and calcium transients under the CNT electrode (bottom) during seizure-like events. Two-photon images for dashed timelines on calcium transients (right). Scale bar: 10 µm (right). d Schematic illustration with highlighted features of a hydrogel-based transparent electrode. e Transmittance versus wavelength plot for hydrogel-based electrode materials. f Hydrogel-based and conventional electrode on the complicated surface of porcine brain. The hydrogel electrode performs better in terms of transparency and conformality to the surface. Scale bar: 10 mm (left), 5 mm (right). g 4 × 4 Zinc-Oxide-based (ZnO) transparent micro-opto-electrode array (MOA). Optogenetic stimuli was transmitted through the ZnO electrodes and emitted from the tip as waveguides. These pinpointed stimulations minimize spatial mismatches between the electrical and optical modalities. Scale bar: 1 mm. h High-powered optical stimulation to the motor cortex prompted various body movements. In the case of optoelectrode 9, both forelimbs reacted and corresponding electrical recordings are plotted. i Electrical recordings from an MOA when various powered optical stimulations were given to optoelectrode 16. j Transparent PEDOT:PSS-EG neural electrode array for simultaneous electrophysiology with optogenetics. k 473 nm light stimulation upon the electrode of Au array (Top) and PEDOT:PSS-EG array (Bottom), respectively. l Electrophysiological color-heatmap from light evoked signal response with conventional Au electrode array (Top) and transparent PEDOT:PSS-EG electrode array (Bottom). Panel a, b, and c adapted with permission from ref. ²⁷, American Chemical Society. Panel d, e, and f adapted with permission from ref. ¹²⁹, Springer Nature. Panel g, h, and i reprinted from ref. ¹⁴⁴, Springer Nature. Panel j, k, and l adapted with permission from ref. ¹⁵⁴, Springer Nature.