Humidity sensor based on tapered no-core fiber coated with Ti₃C₂T_x MXene

An optical fiber relative humidity (RH) sensor based on tapered no-core fiber (TNCF) coated with Ti₃C₂T_x MXene is proposed. The fluoride etching method is used to prepare Ti₃C₂T_x, which is used as the humidity sensitive material with a multi-layer structure, large specific surface area and rich hydrophilic groups, and optical deposition method is used to integrate Ti₃C₂T_x with TNCF. The diameter of TNCF between two sections of SMF is reduced to 11.6 μm to enhance RH sensitivity. The refractive index (RI) of Ti₃C₂T_x changes as a result of variations in RH, and this ultimately causes a shift in the transmission spectrum. The sensitivity of the device is −77 pm/%RH in the range of 33 %RH to 75 %RH. In the region of 75 %RH to 91 %RH, the sensitivity increases to 685 pm/%RH, the linear correlation coefficients of the two regions are 0.9521 and 0.9940, respectively. On average, the response time is approximately 3.5 s and the recovery time is about 12.7 s. The sensor may be utilized in possible domains, including biological, chemical, and food processing. Its benefits include a simple construction, cheap cost, high reversibility, and stability.