Protein-based photocell for high-speed motion detection

A high-speed motion detection system that utilizes bioelectronic photocells is described in this paper. Each individual photocell consists of a sandwich-structural device with an ITO (indium tin oxide) electrode/bR film/ITO electrode configuration. During illumination, the molecules in the thin bacteriorhodopsin (bR) film undergo a multi-state photocycle followed by a proton transport from the cytoplasmic side to the extracellular side of the cell membrane. Both the wavelength and intensity of the impinging light source influence the charge displacement and, thereby, the current flow. Experimental studies show that the bR photodetector measured by the current mode exhibits a wide dynamic range and very fast response time. The photoelectric response is approximately linear over the light power range of muW to W. The response time is related to the bR photocycle kinetics and has been measured in mus. The responsivity of the experimental photocell is ISO mV/mW at 570nm. In addition, the device exhibits a high degree of differential photosensitivity to change in incident light intensity. These photoelectric properties make bR film a viable material for designing spatio-temporal motion detection systems. Issues related to the design and fabrication of a high-resolution and high-speed motion detection system for machine vision applications are discussed