Wearable temperature sensor with moisture resistance based on MXene-embedded fiber

As climate change intensifies, summer temperatures are gradually rising, resulting in an increase in heat-related illnesses among individuals exposed to heatwaves. Consequently, wearable sensors for external environmental monitoring are gaining prominence as personal healthcare and safety diagnosis systems. Wearable temperature sensors must provide stable sensing even when subjected to various external environmental changes, such as repetitive movement, humidity, and water contact. In this study, a fiber-type temperature sensor with an embedded MXene (Ti3C2Tx) was fabricated. MXene was synthesized by etching aluminum (Al) from Ti3AlC2 (MAX phase powder) using a mixture of Li salt and hydrochloric acid (HCl) and then prepared as an aqueous dispersion. Subsequently, conductive fibers were fabricated by embedding MXene into polyester fibers via a dipping–drying process. To mitigate susceptibility to moisture, hydrophobic 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecylphosphonic acid (HDF-PA) was applied to the surface of the MXene embedded in the fiber, providing hydrophobicity. The temperature range of 0–50 °C was monitored by measuring the resistance change in the fabricated HDF-PA-coated MXene-embedded fiber. Furthermore, sensing characteristics remained robust even under a bending radius of 15–3 mm. In addition, the sensor was confirmed to operate stably despite physical deformation from repeated bending up to 1000 times, as well as exposure to 50%–90% RH and 1 h of immersion in water, demonstrating excellent durability and water resistance.