An optically controlled microfluidic chip is provided for administering a fluid to a neuronal site. The chip is made of at least one unit or pixel, each of which constitutively emits fluid in the dark, and reduces emission of fluid in response to light. The individual pixels are capable of being individually controlled, thereby translating a spatial pattern of incident light into a spatial pattern of neuronal stimulation. Each pixel contains a housing, an aperture in the housing, and a reservoir containing fluid that is connected to the aperture. The aperture is designed to allow continuous emission of fluid from the reservoir through the aperture when the pixel is in the dark. Each pixel also includes an optical control, which reduces the emission of fluid from the reservoir through the aperture in response to light.