High Sensitivity Humidity Detection Based on Functional GO/MWCNTs Hybrid Nano-Materials Coated Titled Fiber Bragg Grating.

Fang Wang,Mengdi Lu,Xuhui Zhang,Bowen Wang,Changsen Sun,Yang Zhang,Wei Peng

doi:10.3390/nano11051134

Abstract

A high performance humidity sensor using tilted fiber Bragg grating (TFBG) and functional graphene oxide (GO)/multi-walled carbon nanotubes (MWCNTs) hybrid nano-materials was proposed. The humidity-sensitive material with three-dimensional (3D) structure was synthesized by the MWCNTs and GOs. Comparing with traditional two dimensional (2D) GOs film, water molecules could be absorbed effectively due to the larger ripples and more holes in GO/MWCNTs layers. The water molecule will fill the entire space in the 3D structure instead of air, which further enhances the absorption efficiency of the hybrid nanomaterial. TFBG as a compact and robust surrounding complex dielectric constant sensing platform was utilized. The mode coupling coefficient or the amplitude of TFBG cladding mode will vary sharply with the imaginary part of permittivity of the hybrid nanomaterial, realizing the high performance RH sensing. In the experiments, we successfully demonstrated that this 3D structural nanomaterial composed by the MWCNTs and GOs has significant advantages for expanding the range of humidity detection (range from 30% to 90%) and enhancing the detection sensitivity (0.377 dB/% RH is twice more than humidity sensor with 2D GO film). The TFBG-based RH sensor also exhibits good repeatability and stability. Our proposed humidity sensor has potential application in environmental and healthy monitoring fields.

Highlights

Accepted: 23 April 2021Humidity monitoring has taken an important role in numerous areas such as corrosion protection, precision electronics manufacturing, food processing, and other industries [1,2,3].Traditional humidity sensors are mainly based on electric, gravimetric, and thermal conductive technology including capacitive type, resistive type, and photoelectric type humidity sensors [4,5,6,7,8]
It exhibited good linearity under the relative humidity (RH) changing from 30% to 65%, and the RH sensitivity was
The graphene oxide (GO)-coated tilted fiber Bragg grating (TFBG) sensor could be used for humidity detection in the environment, the limits of sensitivity and humidity detection range still need to be resolved

Summary

Introduction

Humidity monitoring has taken an important role in numerous areas such as corrosion protection, precision electronics manufacturing, food processing, and other industries [1,2,3]. Nanomaterials 2021, 11, 1134 effects of these methods, fiber Bragg grating (FBG)-based humidity sensors have been demonstrated [15,16]. FBG could excite a lot of high order cladding modes with the titled grating plane This unique feature enables the TFBG to directly sense the complex permittivity of the surrounding medium. Graphene oxide (GO) as a derivative of graphene is stable in aqueous solution and polar solvent It has a large number of oxygen-containing groups on surface and edge that can permeate and absorb water molecules, making GO a good candidate for humidity-sensitive material [29,30]. We proposed a TFBG-based humidity sensor with GO and evenly dispersed multi-walled carbon nanotubes (MWCNTs) hybrid humidity-sensitive nanomaterial. The proposed sensor with good performance will show good potential applications for health and environmental monitoring in many fields

Principle and Experimental System

Experimental Results and Discussion

Conclusions