A High-SNR Wearable Respiratory Monitoring System with Directional Airflow Sensing Enabled by Triple-Asymmetric Magnetic Microcolumn Arrays.

Sleep disordered breathing (SDB) calls for the continuous and reliable monitoring of respiratory airflow. In clinical practice, polysomnography (PSG) commonly measures nasal airflow using cannulas or masks that confine the flow path, which often reduce comfort and may disturb natural sleep. Measuring airflow directly in open air would be more convenient, but it is prone to interference from ambient airflow, temperature, and humidity, and most existing sensors do not provide information on flow direction. Here, we report a directional open-path respiratory airflow sensor based on a triple-asymmetric magnetic microcolumn array (TAMMA) and further demonstrate its integration into a wearable eye-mask platform. The structure combines a magnetic top segment with a flexible support and introduces asymmetry in geometry and spatial arrangement. As a result, the array responds strongly to airflow normal to the sensor while showing minimal response to parallel disturbances, which improves robustness in practical environments. The sensor detects airflow down to ∼5 L/min over a working range of 5-40 L/min, with two separate linear response ranges of 5-20 and 20-40 L/min, both with R2 = 0.99 and a signal-to-noise ratio up to 41 dB. After establishing the sensor-level directional airflow sensing performance, we integrated the TAMMA sensor with miniaturized electronics and wireless transmission to construct a proof-of-concept eye-mask system for sleep respiratory monitoring. The system distinguishes inhalation from exhalation, records respiratory airflow waveforms during sleep, and captures airflow features associated with abnormal breathing patterns, including hypoventilation and apnea-like events. This work establishes a wireless magnetic sensing strategy for high-SNR, direction-resolved open-path respiratory airflow detection and provides a feasible platform for future home-based sleep respiratory monitoring.