Waterproof breathable multifunctional flexible sensor for underwater tactile sensing and ammonia gas monitoring

Flexible wearable multifunctional sensors play a vital role in health monitoring, electronic skin, and hazardous gas detection. While combining excellent sensing performance, it is still a challenge to prepare an electronic device with practical properties to increase wearing comfort and adaptability to harsh environments. Herein, we present a multifunctional sensor based on PA6 composite fibers, exhibiting outstanding sensitivity to different external stimuli. For the tactile sensor, we have successfully adjusted the sensitivity and linear range by introducing a spacer layer to improve the linearity by 21.6 times. Benefiting from its intricate and rich fiber structure, the multi-layer fiber-based ammonia sensor has a high sensitivity and a lower detection limit. The multifunctional sensor leverages the dual properties of its outer hydrophobic PA6/PS composite fibers and inner hygroscopic PA6 nanofibers, effectively bolstering its resistance to humidity. Furthermore, the breathability and waterproofness make the sensor promising for rainfall monitoring, underwater pulse/behavior monitoring, etc. Notably, a wireless underwater monitoring system has been designed, confirming the feasibility of underwater calling for help, further demonstrating the potential applicability of our work in the underwater communication.