Abstract: Respiratory diseases can be monitored early and warned through multiple respiratory parameters. As the core component of respiratory state monitoring, humidity sensors have inherent defects such as high cost, rigid substrate and low portability. This paper proposed a new wearable humidity sensor based on BaTiO₃ and laser induced graphene (LIG) interdigital electrodes.The efficient “one-step” process of LIG interdigital electrodes was achieved through laser direct writing technology. The results show that LIG presents a unique honeycomb-like three-dimensional porous structure. This structure effectively increases the specific surface area of the humidity-sensitive layer and provides more adsorption sites for water molecules.The BaTiO₃/LIG sensor has excellent capacitive response/recovery performance, cyclic stability, and mechanical properties in the relative humidity range of 11%~97%. When applied to human respiratory monitoring, the device can sense and record respiratory signals in real time. By analyzing the peak shape, intensity, half-peak width, fluctuation and respiratory cycle time of the capacitance curve, different respiratory organs, respiratory frequencies and respiratory distances can be identified, which is of great value for intelligent medical diagnosis.

Key words: humidity sensor, BaTiO₃, graphene, respiratiory monitoring, flexibile