Highly Sensitive Temperature Detection Based on a Frost- and Dehydration-Resistive Ion-Doped Hydrogel-MXene Composite

Wearable temperature sensors with high sensitivity and stability hold great potential for human health monitoring. However, hydrogels, which are commonly used for wearable devices, often show poor thermal and electrical conductivity and are susceptible to dehydration and freezing. Herein, we developed a frost- and dehydration-resistive temperature sensor based on Fe²⁺/Ti₂CT_x/κ-carrageenan (CA)-polyacrylamide (PAM) hydrogel. The Fe²⁺ ions within the hydrogel existed in two forms: as free ions and bonded ions. The free Fe²⁺ ions could complex with water molecules, resulting in the improved resistance to dehydration and freezing, as well as enhanced ionic conductivity in the hydrogel. On the other hand, the remaining Fe²⁺ ions acted as linkers to form coordination bonds with the sulfate groups of CA chains, resulting in the greatly enhanced mechanical strength of the hydrogel. In addition, the Ti₂CT_x nanosheet-based fillers formed a well-defined porous laminar structure, which reduced the phonon scattering and improved the phonon adsorption within the hydrogel. The Fe²⁺/Ti₂CT_x/CA-PAM hydrogel sensor exhibited excellent temperature sensing performance including a good linearity (R² = 0.998) within a broad working range (−10 to 60 °C), high resolution (0.1 °C), and good repeatability. Furthermore, the sensor was integrated into a wireless system for continuous monitoring of body temperature, demonstrating its potential in healthcare monitoring, electronic skins, and intelligent robots.