Polymer microfiber coated with ZnO for humidity sensing

Abstract

A PMMA microfiber that is coated with ZnO is employed as a relative humidity sensor. The PMMA microfiber with a diameter of 60 μm is fabricated by using a direct drawing method from molten PMMA. Then, the fiber is coated with ZnO that is prepared from sol - gel immersion method. There are two types of coating done for this work, namely ZnO nanostructures and nanorods respectively. The experimental setup for the proposed sensor comprises of an amplified spontaneous emission (ASE) light from Erbium-doped filber amplifier (EDFA), sealed chamber and an optical spectrum analyser (OSA). The variation of the output power of the ASE with relative humidity is recorded. It is observed that the output power for PMMA microfiber coated with ZnO nanostructures decreases from -22.43 to -27.87 dBm as the humidity is increased from 50% and 80%. The performance of the proposed sensor is enhanced after being coated with ZnO, for both nanostructures and nanorods. The results show that the sensitivity of the sensor when it is coated with ZnO nanostructures has improved from 0.1191 dBm/% to 0.1791 dBm/%. When ZnO nanorods are coated onto the PMMA fiber, the performances of the proposed fiber further improved with the sensitivity increases to 0.2159 dBm/%. This proposed sensor provides numerous advantages such as higher mechanical strength and low cost of production. In addition, it is highly suitable for continuous monitoring of relative humidity in compact areas.