Multifunctional and Flexible Sensor Based on PU-Supported Ti₃C₂T_x/TiO₂/PPy Yarns for Ammonia Sensing and Human Motion Monitoring

With the rapid advancement of wearable technology, multifunctional sensors have garnered significant attention due to their potential applications in environmental monitoring, health diagnostics, and human−machine interaction. Despite their promise, challenges, such as limited flexibility, insufficient sensitivity, and complex production processes, have hindered their practical deployment. This study presents the fabrication of a multifunctional flexible sensor based on PU-supported Ti 3 C 2 T x /TiO 2 /PPy yarns for both ammonia (NH 3 ) gas sensing and human motion detection. Key innovations include the incorporation of polypyrrole (PPy) into the Ti 3 C 2 T x MXene structure and the optimization of titanium dioxide (TiO 2 ) content through varying hydrothermal times, which significantly enhance the gas sensing performance. The sensor demonstrates exceptional sensitivity and selectivity toward NH 3, with a rapid response and recovery times. Additionally, the PU-supported composite yarns exhibit excellent mechanical flexibility and durability, maintaining stable performance under repeated stretching and bending cycles. In human motion detection, the sensor shows high sensitivity and reliable performance in monitoring various physical activities, making it highly suitable for applications in wearable electronics. These features ensure the sensor’s applicability in diverse settings, promoting safety and health in environments with potential ammonia exposure and enhancing human−machine interactions through accurate motion monitoring.