Hierarchically Engineered MXene/CMC-Na Composites with Acetaminophen Modification for Self-Powered Humidity Sensing.

Humidity sensors have demonstrated significant potential for applications in wearable electronics, physiological monitoring, and environmental sensing. However, the practical implementation of humidity sensors is often limited by reliance on external power sources, making the development of self-powered humidity sensing systems a considerable challenge. This work presents a hierarchical multi-step modification strategy to fabricate an acetaminophen (AP)-modified hydroxylated MXene/carboxymethylcellulose sodium (CMC-Na) hybrid gel ink (AHMC) with integrated humidity sensing and self-powered functionality. Theoretical calculations reveal that AHMC exhibits exceptional water adsorption capacity, characterized by a lower adsorption energy (-0.42 eV) and a shorter adsorption distance (1.69 Å) compared to MXene. The screen-printed paper-based AHMC humidity sensor (PB-AHMC) demonstrates a rapid capacitive response (4.8/0.6 s) and remarkable response (73524%) with excellent bending stability and environmental durability. Furthermore, the PB-AHMC-based humidity sensor array (PCSA) accurately identifies various subtle respiratory abnormalities with the incorporation of machine learning algorithms. Significantly, a self-powered sensor (SP-AHMC) driven by redox reactions has been developed, achieving a broad detection range (11%-97% RH), exhibiting minimal hysteresis (1.0% RH), and delivering a peak output voltage of 0.43 V at 97% RH. Collectively, the AHMC-based sensors demonstrate substantial potential for advancing applications in healthcare monitoring, non-contact humidity detection, and self-powered systems.