GO/MoS2@PVA composite membrane-based optical fiber Mach–Zehnder interferometer for humidity sensing and its non-contact sensing application

A humidity sensor based on an optical fiber Mach–Zehnder interferometer (MZI) coated with a GO/MoS 2 @PVA composite membrane was investigated for non-contact sensing. MoS 2 was used as a nanospacer to enhance the humidity-sensitive properties of GO, and the adhesion and stability of the composite membrane on the fiber surface could be increased by PVA. The proposed sensor shows a maximum sensitivity of 0.26 dB/%RH with average response and recovery times of 1.62 and 1.11 s, respectively. In non-contact sensing applications, the sensor can effectively recognize a maximum distance of 10 mm for the proximity of a human finger with a distance variation interval of 3 mm. The proposed sensor is expected to be applied in non-contact distance detection and localization or as a non-contact human–computer interaction panel.