Ultra-Sensitive Fiber-Optic Spr Humidity Sensors Based on Cellulose Prepared from Licl/Dmac System

Abstract

This article introduces a temperature-compensated ultra-high sensitivity fiber surface plasmon resonance (SPR) humidity sensor. We coat a gold film on a plastic-coated multimode optical fiber and apply cellulose as a humidity-sensing material on the surface of the gold film. When environmental humidity changes, the cellulose material absorbs or releases water molecules, leading to a variation in its refractive index (RI). The experimental results show that as the relative humidity (RH) increases, the resonance wavelength (RW) exhibits a blue shift. Within the range of RH from 25% to 70%, the average sensitivity of the sensor is -9.56 nm/RH%, and the highest sensitivity is -14.25 nm/RH%. In addition, we cascaded the sensor with a fiber SPR temperature sensor based on polydimethylsiloxane (PDMS) to achieve temperature compensation. The experimental results show that the temperature sensitivity is -2.37 nm/℃ within the range of 25 ℃ to 45 ℃. Finally, by monitoring the changes in temperature and humidity based on the changes in the two RWs, combined with the sensitivity coefficient matrix, we can simultaneously obtain the changes in humidity and temperature, while also achieving temperature compensation. This sensor exhibits ultra-high humidity sensitivity and has great potential in practical applications such as human respiration detection and human health analysis due to its simple structure.

Keywords: CelluloseRefractive indexSilica fiberSPRHumidity measurementHigh sensitivity