Light-addressable planar electrode with hydrogenated amorphous silicon and low-conductive passivation layer for stimulation of cultured neurons

Conventional multielectrode arrays (MEAs) cannot always access desired neurons due to low electrode density and small number of electrode. To overcome this problem, we propose a light-addressable planar electrode on a glass substrate. The electrode has a 3-layer structure, namely a transparent SnO₂ layer, an hydrogenated amorphous silicon (a-Si:H) layer, and a passivation layer. Illumination to the a-Si:H layer increases the conductivity of a-Si:H and creates a virtual electrode at the surface of the illuminated site. In the present study, we developed a low-conductive zinc antimonate-dispersed epoxy layer. This layer could successfully prevent penetration of culture medium and thus deterioration of a-Si:H layer. A fluo-4 calcium imaging demonstrated that, when the whole area of electrode was illuminated, negative-monophasic voltage-controlled pulses could also successfully activate neurons cultured on the electrode. Moreover, the focused illumination to the electrode resulted in the selective activation of neurons around the illuminated area