Abstract: In some embodiments, the invention provides tissue-on-a-chip and organ-on-a-chip devices with integrated, on-board photonic integrated circuit optical sensors that allow real-time detection of analytes released from cells disposed on either side of a porous, ultrathin membrane within the device. The invention further provides modular devices for studying cells and interactions between and among cell types. The devices and methods using them are useful for, among other thing, modeling the biological and physiological interactions of cells of different tissue types, allowing high-throughput screening of drug candidates, and informing safety and efficacy in a virtual clinical trial.