Wang, Yusheng.; Kim, Miles.; Fan, Hanwen.; Ge, Ruijian.; Wang, Darren.; Maldonado, Fabien.; Demarest, Caitlin.; Zhou, Yuxiao.; Dong, Xiaoguang. (2026).Ìý.ÌýScience Advances, 12(16), eaed3998.Ìý
Monitoring the airways continuously inside the body is important because it could help doctors detect problems early. Most current systems need chips and batteries, but a newer approach uses inductive coupling, which means the sensor can be powered and read wirelessly through magnetic fields, so it does not need its own battery. The challenge is that existing chip-free sensors usually can measure only one type of signal because they work over a limited frequency range. To solve this, the authors developed a tiny magnetic switch that can be controlled wirelessly by an external magnetic field. It uses a small cantilever beam, a flexible structure that bends and moves, to anchor, rotate, and switch between different sensing channels. When combined with an inductive coil and capacitive sensors, which detect changes in electrical signals caused by physical changes, the device produces resonance-based signals that can be picked up wirelessly with a vector network analyzer, an instrument that reads these signals. The system was shown to measure tissue stiffness by switching between two modes, map pressure across time and space, and detect multiple properties of mucus at once. Overall, this magnetic switch could help enable small, smart airway devices for continuous, minimally invasive, and multi-purpose monitoring in a range of airway diseases.
Fig. 1. Concept of the magnetic switch enabled sensory ring for wireless, chip-free, battery-free, and multimodal sensing in the airway.
(A) Concept of the sensory ring and self-expandable airway stent implanted inside a human trachea for wireless monitoring of airway conditions, such as tissue stiffness, pressure, temperature, and mucus conditions for disease diagnosis. (B) Illustration of the magnetic switch enabled multichannel LC circuit. (C) Illustration of the conversion from tissue properties to readout resonant frequencies. (D) Illustration of the readout signal from the VNA reader device. Different frequency curves are overlaid in the same figure to show the shift of the peak frequency. (E) Illustration of the chip-free wireless sensing mechanism based on radio frequency. (F) Schematics of the components inside the sensory ring including the magnetic switch, induction coil, and capacitive sensors. (G) (i) Optical image of an example sensory ring with no on-board chips for sensing pressure and tissue stiffness. The dashed box indicates a pressure sensor on the inner surface of the sensory ring. (ii) Optical image of an example sensory ring with no on-board chips for sensing mucus layer thickness and temperature. The dashed box indicates a temperature sensor on the inner surface of the sensory ring. (H) Optical image of a self-expandable metallic airway stent sutured with a sensory ring.