Azobenzene-Based Gel Coated Fibre Bragg Grating Sensor for Moisture Measurement

Abstract

A fibre Bragg grating sensor is coated with a novel polymer gel in order to investigate its suitability for nondestructive measurement of moisture in materials that can potentially lose their integrity due to moisture ingress. Absorption and desorption of moisture lead to swelling/shrinkage of an azobenzene-based gel, which induces a strain in the Bragg grating resulting in wavelength shifts. The results demonstrated that the amount of wavelength shift is linearly dependent on the amount of water ingress by the gel. The performance of the proposed optical fibre moisture sensor was found to be repeatable with no detectable hysteresis and has the potential to offer a low-cost route for monitoring moisture content.

Corrosion-Induced Mass Loss Measurement under Strain Conditions through Gr/AgNW-Based, Fe-C Coated LPFG Sensors

“…The mass loss and resonant wavelength were measured and correlated through the same procedure in previous work. The shift in measured resonant wavelength was also used in Equations (5,6) to determine the estimated mass loss.…”

“…Let η m be the measured mass loss, η c1 be the mass loss calculated using the zero-strain η-∆λ correlation or the first expression in Equation 4, and η c2 be the mass loss calculated from the general η-∆λ expressions in Equation (5). The calculated mass losses were compared with the measured one in Table 1 to evaluate the error of different equations used.…”

“…For example, Fiber Bragg Grating (FBG) [3] and Brillouin Optical Time Domain Analysis (BOTDA) [4] were utilized to measure the corrosion induced strain on steel rebar. FBG sensor coated with a functional polymer layer was utilized for moisture measurement in concrete [5]. Even though these methods can measure the indirect parameters precisely, the correlation between these parameters and the mass loss of steel rebar or members remains unknown due to the complicated corrosion process and environment.…”

Fluorescent Azobenzene-Containing Compounds: From Structure to Mechanism

“…Since the discovery of azobenzene's isomerization in 1937 [1], it has shown great potential for use in liquid crystals [2][3][4][5][6][7][8], sensors [9][10][11][12][13], molecular photoswitches [8,[14][15][16][17][18], information storage [19][20][21], etc. due to its unique and remarkable properties, including the ability to undergo reversible cis-trans isomerization upon photo-irradiation at specific wavelengths.…”