Monolithic Electronic-Biophotonic System-on-Chip for Label-Free Real-Time Molecular Sensing

Label-free miniaturized optical sensors can have a tremendous impact on highly sensitive and scalable point-of-care (PoC) diagnostics by monitoring real-time molecular interactions without any labels. However, current biophotonic platforms are limited by complex optical and external readout equipment, precluding their use in a PoC setting. In this work, we address this challenge by developing a first-of-its-kind fully integrated electronic-photonic label-free molecular sensor utilizing microring resonators (MRRs) co-integrated with on-chip electronics in a high-volume advanced electronic process. In particular, we present an arrayed electronic-photonic system-on-chip (EPSoC) in GlobalFoundries (GF) 45-nm RFSOI with 60 5- $\mu$ m radius MRRs connected to on-chip receivers, approaching an idealized limit of detection (LoD) equivalent to a single 140-nm viral particle. To further enhance the LoD, we propose a dual-ring phase-based sensing architecture, boosting the system's sensitivity by 3.7 $\times$ compared to our previously reported intensity-based single MRR scheme. An integrated heater embedded in the design of the ring and an on-chip controller locks the ring's resonance at the desired point of operation, eliminating the need for a tunable laser. The inherent intrinsic limitations of MRRs due to ambient temperature variations are addressed with an on-chip differential scheme using sensing and reference rings to cancel common mode errors. We demonstrate the sensing capabilities of the EPSoC by monitoring in real-time binding events of bovine serum albumin (BSA), anti-BSA molecules, and streptavidin-coated nanoparticles, unlocking the door toward self-contained fully integrated lab-on-chip (LoC) photonic sensors for PoC applications.