Ultrahigh Sensitivity of Flexible Thermistors Based on 3D Porous Graphene Characterized by Imbedded Microheaters

It is important to develop highly sensitive, accurate, and easy-calibration flexible temperature sensors for emerging wearable applications. Here, ultrasensitive and flexible temperature sensors are developed using 3D porous graphene (Gr) synthesized by microwave plasma-enhanced chemical vapor deposition as the channel transducing material, and the liquid crystal polymer as flexible substrate. Thanks to the porous structures, enormous defects, and oxygenated groups incorporated in Gr, the thermistor displays the remarkable thermal index of 3193 K, higher than those of most existing Gr-based thermistors and comparable to those of ceramic-based rigid thermistors. The imbedded microheaters on the same device are exploited to characterize and calibrate the thermistors, as well as reduce the oxygen-containing Gr in situ, bypassing the requirement of conventional external bulky hot plates. The thermal indexes are generally stable regardless of thermal annealing, but decrease slightly with prolonged reduction time of Gr. Attributing to the porous structure for effective heat dissipation, a short recovery time of 9.3 s is attained. The high sensitivity and resolution (0.1 °C) of the thermistors enable various practical applications, such as noncontact sensation, human skin, and wind temperature monitoring, etc. This work develops a 3D porous Gr based “self-calibration” thermistors with competitive performance.