Image sensing and processing by a bacteriorhodopsin-based artificial photoreceptor.

Sensing and processing of optical information have been conducted with a unique bioelectronic image sensor that immobilizes bacteriorhodopsin (bR) as a photosensitive retinal protein. A thin film of bR-containing purple membranes was coated on a two-dimensional pixel array of electrodes and was made into a junction with an electrolyte gel layer having a counterelectrode to form an artificial photoreceptor. Photocurrent signals from each pixel showed a differential responsivity to light intensity, intrinsic to this liquid-junction photocell. Images detected and processed by the bR-based artificial photoreceptor were simultaneously displayed on a light-emitting-diode monitor panel through parallel signal-transmission circuitry. The experiment revealed that the photoreceptor is, as a retina model, capable of selectively detecting motion of images in real time and of performing vectorial extraction of their edge components, similar to the visual processing function of biological photoreceptors.