▎ 摘　　要

Graphene-based micro/nanoscale materials have not been used much for thermal sensing while they have great potential advantages over current sensors for micro/nanoscale measurement. This work reports on the discovery of ultra thermal sensing capability, especially at cryogenic temperatures for graphene microfibers (GMFs). From 295 K down to 11 K, the electrical resistance of GMF increases by around five orders of magnitude (105-fold). GMF's extreme thermal sensitivity is explored by using it for dynamically measuring its thermophysical properties. At 25 K, a temperature change as small as 0.027 K can be sensed with high confidence. Moreover, the fibers still have extreme sensitivity after current annealing. When the annealing temperature becomes higher, the microstructure of the material improves considerably, thereby ensuring application robustness in thermally hostile environment. GMF presents a novel ultra-sensitive material for temperature measurement at the micro/ nanoscale, especially at cryogenic temperatures while its temporal response can reach a level of ms.