Direct-Writing MXene/Polypropylene Composites for Wearable Humidity Sensors With Multiple Applications

Wearable humidity sensors have attracted extensive interest because of their affordability, high sensitivity, portability, and ease of use in the rapidly developing fields of noncontact medical diagnostics, healthcare monitoring, and environmental sensing. However, achieving a high-performance and stable wearable humidity sensor for healthcare monitoring, such as respiration, is still challenging. In this work, we propose a simple direct-writing method for the in situ fabrication of wearable resistive-type humidity sensors based on Ti3C2Tx metal carbides/nitrides (MXene). The sensing performance of MXene/PP composite-based humidity sensors has been thoroughly investigated, including sensitivity (0.601%/%RH), response/recovery time (17/37 s), and stability (20 h under 84% RH). Moreover, we demonstrate that the proposed wearable humidity sensor can accurately recognize different breathing patterns and monitor human respiration in real time, enabling the evaluation of physiological conditions for early warning. In addition, it can easily monitor sleep quality and rapidly identify any issues with mask use. Even more, an MXene/PP composite-based humidity sensor matrix can be applied for noncontact gesture tracing. Therefore, this work provides a practical solution for the fabrication of wearable, high-performance humidity sensors for individualized healthcare monitoring in real time, which paves a solid path for the creation of personalized healthcare monitoring devices.