Time-variant electrical equivalent circuit of a dry bacteriorhodopsin sensor

Modeling the photoelectric response of dry bacteriorhodopsin (bR) sensors has commonly been carried out by following the theory of linear time-invariant systems. However, it has been reported that the time constants of the photovoltage responses of such sensors vary depending on whether the sensor is measured when the incident light is switched on or off. In this paper, we propose an electrical equivalent circuit for dry bR sensors. Unlike the models presented in the literature, the proposed circuit also considers the illumination on the bR sensor. The model is experimentally verified by photocurrent measurements. Further, a new result concerning the photocurrent dependence on the illumination of dry bR sensors is introduced.