A miniature magnetic switch unlocking multimodal, chip-free, and batteryless airway sensing

Continuously monitoring airway physiological properties in situ is critical for enabling early intervention. Unlike conventional approaches relying on on-board chips and batteries, chip-free sensing based on inductive coupling offers a promising pathway for fully wireless and battery-free monitoring. However, current chip-free strategies are limited in achieving multimodal sensing due to their narrow operational frequency ranges. Here, we introduce a miniature magnetic switch that enables wirelessly controlled channel switching through a cantilever beam mechanism, which anchors, rotates, and toggles between channels in response to external magnetic fields. Integrated with an inductive coil and capacitive sensors, the system generates resonance-based signals that can be selectively and wirelessly detected using a vector network analyzer (VNA). The concept is demonstrated through sensing tissue stiffness by switching between deformation and stress sensing modes, spatiotemporal mapping of tissue pressure, and multimodal sensing of multiple mucus properties. The proposed magnetic switch thus enables next-generation smart airway devices for continuous, minimally invasive, and multimodal sensing in diverse airway diseases.