Thermosensitive MXene-Based Flexible Wearable Sensors for Multifunctional Human Signals Monitoring

We developed a multifunctional wearable sensor that can monitor temperature and take anisotropic strain measurements in real time. The material used in this study consisted of covalently cross-linked N-isopropylacrylamide (NIPAM), Ti3C2Tx MXene nanosheets, and Nanoclay particles. The conductivity of the material was then significantly improved (up to 4.762 S/m) by the addition of Fe3+ ions, which interact with the surface of MXene nanosheets. Moreover, the secondary physical networks created by the nanoclay particles, MXene, and Fe3+ ions provided energy dissipation and improved the critical strain and toughness by 75 and 250%, respectively. After incorporating the hydrogel into a flexible sensor, we discovered and characterized a unique anisotropic resistance when taking measurements at different angles with respect to loading. The developed sensor has great strain sensitivity (gauge factor of 1.28), a fast response time (120 ms), and a broad working strain range (≈ 400%), thus, illustrating promise as a versatile sensor for human signal monitoring.