Self-Calibrated, Sensitive, and Flexible Temperature Sensor Based on 3D Chemically Modified Graphene Hydrogel

During the long-term operation of temperature sensors, periodical calibration is required to achieve accurate readings, which usually requires bulky and costly heating facilities for calibration. Herein, a new kind of self-calibrated thermistors using embedded microheaters as a self-heating platform are proposed for in situ, convenient, cost-effective, and fast self-calibration. Furthermore, the thermal sensing properties of 3D reduced graphene oxide hydrogel (RGOH) is explored for the first time based on this microheater platform. It is found that the a 3D sulfonated RGOH (S-RGOH) based thermistor displays high sensitivity (2.04% K⁻¹), extraordinary resolution (0.2 °C), a broad detection range (26–101 °C), good repeatability, and stability. The thermal sensitivity of S-RGOH is far superior to that of pristine RGOH, revealing the remarkable role of chemical modification in enhancing temperature sensing performance. In addition to self-calibration, the microheaters are also used for characterizing temperature-dependent properties and thermal annealing of S-RGOH in situ. The thermal sensing mechanism is proposed and the high sensitivity is discussed by considering the abundant functional groups, defects, and 3D porous structure of S-RGOH. The flexible S-RGOH thermistor fabricated on a liquid crystal polymer substrate is immune to mechanical flexion, allowing for various practical applications in future wearable electronics.