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Photonic technologies promise to deliver quantitative, multiplex, and inexpensive medical diagnostic platforms by leveraging the highly scalable processes developed for the fabrication of semiconductor microchips. However, in practice, the affordability of these platforms is limited by complex and expensive sample handling and optical alignment. We previously reported the development of a disposable photonic assay that incorporates inexpensive plastic micropillar microfluidic cards for sample delivery. That system as developed was limited to singleplex assays due to its optical configuration. To enable multiplexing, we report a new approach addressing multiplex light I/O, in which the outputs of individual grating couplers on a photonic chip are mapped to fibers in a fiber bundle. As demonstrated in the context of detecting antibody responses to influenza and SARS-CoV-2 antigens in human serum and saliva, this enables multiplexing in an inexpensive, disposable, and compact format.

Decades of research have shown that biosensors using photonic circuits fabricated using CMOS processes can be highly sensitive, selective, and quantitative. Unfortunately, the cost of these sensors combined with the complexity of sample handling systems has limited the use of such sensors in clinical diagnostics. We present a new "disposable photonics" sensor platform in which rice-sized (1 × 4 mm) silicon nitride ring resonator sensor chips are paired with plastic micropillar fluidic cards for sample handling and optical detection. We demonstrate the utility of the platform in the context of detecting human antibodies to SARS-CoV-2, both in convalescent COVID-19 patients and for subjects undergoing vaccination. Given its ability to provide quantitative data on human samples in a simple, low-cost single-use format, we anticipate that this platform will find broad utility in clinical diagnostics for a broad range of assays.