MoS2-based all-fiber humidity sensor for monitoring human breath with fast response and recovery

A humidity sensor is demonstrated using a MoS2-coated etched single-mode fiber (ESMF) and applied in human breath monitoring. Because of the interaction between MoS2 nanosheets and the evanescent field of an ESMF, the light confined within fiber core could be tuned by ambient conditions. The optical frequency conductivity of MoS2 changes with relative humidity variation, so does the transmission light power of the ESMF. A 14 fold enhancement of light power variation in response to human breaths is achieved compared with a bare ESMF. Fast response and recovery speed (0.066 s response and 2.395 s recovery time) enable this sensor to detect human breath in real time. The results also show the feasibility in monitoring different breath patterns related to the breath frequency and depth.