Hetero-core fiber optic humidity sensor with layer-by-layer polymer film including TiO2 nanoparticles using UV light

Abstract

We have developed a hetero-core structured fiber optic humidity sensor with a porous immobilized TiO2 nano-particles. Our research group has been proposed the hetero-core optical fiber humidity sensor due to moisture absorption of the hygroscopic polymer based on optical-intensity modulation. However, the sensor had difficulty in detecting the humidity change at lower humidity range less than 50 %RH. In this paper, we present that the hetero-core fiber humidity sensor has devised to increase the sensitivity at relatively lower humidity by means of including the TiO2 nano-particles in a porous sensitive film comparing to the conventional hetero-core fiber humidity sensor. On the other hand, a UV light has been known to make the TiO2 nano-particles indicate super-hydrophilic reaction and photo catalytic effect. Therefore, the sensitivity of the humidity sensor can be improved using the sensitive film including the TiO2 nanoparticles illuminated by the UV light. We tested the transmitted spectra of UV and visible band light of the proposed hetero-core fiber humidity sensor. As a result, the UV-LED light source could enhance the humidity sensitivity in the proposed hetero-core fiber optic sensor.