Flow sensor based on monolithic integration of organic light-emitting diodes (OLED's) and CMOS circuits
In this paper we present an optoelectronic integrated circuit (OEIC) based on monolithic integration of organic light-emitting diodes (OLED's) and CMOS technology. By the use of integrated circuits, photodetectors and highly efficient OLED's on the same silicon chip, novel OEIC's with combined sensors and actuating elements can be realized. The OLED's are directly deposited on the CMOS top metal. The metal layer serves as OLED bottom electrode and determines the bright area. Furthermore, the area below the OLED electrodes can be used for integrated circuits. The monolithic integration of actuators, sensors and electronics on a common silicon substrate brings significant advantages in most sensory applications. The developed OEIC combines three different types of sensors: a reflective sensor, a color sensor and a particle flow sensor and is configured with an orange (597nm) emitting p-i-n OLED. We describe the architecture of such a monolithic OEIC and demonstrate a meth od to determine the velocity of a fluid being conveyed pneumatically in a transparent capillary. The integrated OLED's illuminate the capillary with the flowing fluid. The fluid has a random reflection profile. Depending on the velocity and a random contrast difference, more or less light is reflected back to the substrate. The integrated photodiodes located at different fixed points detect the reflected light and using cross-correlation, the velocity is calculated from the time in which contrast differences move over a fixed distance.