Humidity-Strain Synergized Adaptive NO Sensing in a Pd-Carbon Nanocoil Fabric for Respiratory-State Recognition

Accurate detection of respiratory apnea requires wearable sensors that can operate reliably under humid and mechanically deformable conditions. Here, we report a dual-stimuli adaptive Pd-carbon nanocoil (Pd-CNC) fabric that integrates humidity, strain, and nitric oxide (NO) sensing within a single wearable platform. By exploiting, rather than avoiding, humidity and mechanical deformation, the fabric exhibits stable room-temperature NO detection with adaptive and accelerated recovery dynamics under realistic breathing conditions. Under combined humidity and strain stimuli, the response to 10 ppm NO is enhanced by 3.2-fold (from 6.6% to 20.7%), while the recovery time constant is reduced from 17360 to 3032 s, demonstrating stimulus-regulated sensing kinetics. Mechanistic studies reveal that preadsorbed water molecules promote NO surface reactions and accelerate desorption, whereas strain facilitates gas diffusion by modulating the fabric microstructure. The sensor also shows excellent long-term stability, maintaining performance after 1 year of storage. In practical demonstrations, humidity pulse sensing enables reliable discrimination between normal breathing and apnea in health subjects, while multimodal humidity-strain-NO analysis allows identification of asthma-relevant respiratory abnormalities under simulated breathing conditions. This work establishes an adaptive multimodal sensing strategy for real-time, noninvasive respiratory monitoring.