Polyaniline/Ti3C2Tx functionalized mask sensors for monitoring of CO2 and human respiration rate

Flexible and wearable gas-sensing devices have become increasingly crucial for monitoring air quality and human health. Disposable masks, mainly composed of polypropylene (PP) fibers, can serve as a potential flexible substrate for sensing devices yet have been largely overlooked during the COVID-19 pandemic. In the present work, flexible Ti3C2Tx/PANI-PP composite gas sensors were fabricated by spray-coating delaminated Ti3C2Tx MXene and in-situ polymerization of aniline on a disposable mask substrate. The resulting hybrid gas sensor displayed a wide detection range (25–1500 ppm), reliable reproducibility, long-term stability, and excellent flexibility and selectivity, a remarkable response (15.2%) towards 500 ppm CO2 gas, which is 6.5 times higher than pristine Ti3C2Tx and 2.4 times higher than pristine PANI. The enhanced sensing performance of the composite sensor is mainly attributed to the synergistic effects of the heterojunctions between Ti3C2Tx and PANI, the improved conductivity, and the enlarged specific surface area. We further investigated the influence of various parameters, including humidity, temperature, bending angles, and folding times on the sensing performance of the composite gas sensor. Finally, a wearable wireless Bluetooth sensing device was fabricated for human exhaled breath monitoring at room temperature, demonstrating the potential application of this Ti3C2Tx/PANI-PP composite sensor for respiratory disease diagnosis.