Light-addressable planar electrode with hydrogenated amorphous silicon and low-conductive passivation layer for...

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.