Smart microplates: integration of photodiode within micromachined silicon pyramidal cavity for detecting chemiluminescent reactions and methodology for passive RFID-type readout

Since the late 1990s our group has been working with groups in chemistry department at the University of Texas at Austin on a project referred as "Electronic Taste Chip," a MicroElectroMechanical System (MEMS) based miniaturized microfluidic chemical sensor with multianalyte detection capabilities. By integrating optical detection mechanism directly onto the silicon chip a cost effective, compact, and portable sensor can be realized enabling use of these chips out of conventional laboratory environment. Addition to the integration a noble approach of accessing a photodiode with non-contact powerless RFID type readout is presented. By doing so a packaged photodiode can be interrogated without direct electrical contact, enhancing the portability even further for a sensor operated in aqueous medium. First background information regarding the project as well as design and integration criteria is presented followed by demonstration of non-contact RFID-type readout of a photodiode. Detailed discussion on the development of process integration scheme is discussed along with the measurements verifying the performance of the fabricated photodiode. During this investigation normally overlooked design criteria of collection efficiency, the effect of how a target element is to be delivered to a detection mechanism on the overall performance of the sensor, is addressed and discussed.