Smart, Gravity-Driven, Dual-Mode, Disposable Evanescent Wave Fluorescent Optofluidic Bio-Nanochip for Rapid and...

The decentralization of biosensing to point-of-need (PON) settings necessitates single-use devices that combine laboratory-level sensitivity with field-deployable simplicity. Existing fluorescent optofluidic chips achieve high sensitivity but rely on bench-top optics, pumps, and trained personnel. Here, we present a smart, disposable evanescent wave fluorescent optofluidic bio-nanochip (DEFOB) that bridges this performance gap. The DEFOB integrates a gravity-driven, 3D-printed microfluidic chip with a functionalized tapered fiber nanosensor, a compact alignment-free all-fiber optical reader, and a smartphone application. This synergistic design enables ultrasensitive, quantitative detection in both homogeneous and heterogeneous assay formats without the need for external pumps or complex peripherals. We demonstrate the platform's versatility through the laboratory-comparable quantification of sulfamerazine antibiotics via immunoassay and of SARS-CoV-2 via an integrated RAA-CRISPR/Cas12b assay, achieving detection limits of 0.06 µg/L and 0.70 copies/µL, respectively. By combining dual-mode operation, high sensitivity, quantitative accuracy, intelligence, plug-and-play functionality, and a low-cost workflow, the DEFOB platform represents a paradigm shift in PON testing, with broad applications in clinical diagnostics, environmental monitoring, and global health security.