Low-cost fully integrated fiber Bragg grating interrogation system

Fiber Bragg gratings can be used for monitoring different parameters in a wide variety of materials and constructions. The interrogation of fiber Bragg gratings traditionally consists of an expensive and spacious peak tracking or spectrum analyzing unit which needs to be deployed outside the monitored structure. We present a dynamic low-cost interrogation system for fiber Bragg gratings which can be integrated with the fiber itself, limiting the fragile optical in- and outcoupling interfaces and providing a compact, unobtrusive driving and read-out unit. The reported system is based on an embedded Vertical Cavity Surface Emitting Laser (VCSEL) which is tuned dynamically at 1 kHz and an embedded photodiode. Fiber coupling is provided through a dedicated 45° micromirror yielding a 90° in-the-plane coupling and limiting the total thickness of the fiber coupled optoelectronic package to 550 µm. The red-shift of the VCSEL wavelength is providing a full reconstruction of the spectrum with a range of 2.5 nm. A few-mode fiber with fiber Bragg gratings at 850 nm is used to prove the feasibility of this low-cost and ultra-compact interrogation approach.

High performance liquid level monitoring system based on polymer fiber Bragg gratings embedded in silicone rubber diaphragm

Liquid-level sensing technologies have attracted great prominence, because such measurements are essential to industrial applications, such as fuel storage, flood warning and in the biochemical industry. Traditional liquid level sensors are based on electromechanical techniques; however they suffer from intrinsic safety concerns in explosive environments. In recent years, given that optical fiber sensors have lots of well-established advantages such as high accuracy, costeffectiveness, compact size, and ease of multiplexing, several optical fiber liquid level sensors have been investigated which are based on different operating principles such as side-polishing the cladding and a portion of core, using a spiral side-emitting optical fiber or using silica fiber gratings. The present work proposes a novel and highly sensitive liquid level sensor making use of polymer optical fiber Bragg gratings (POFBGs). The key elements of the system are a set of POFBGs embedded in silicone rubber diaphragms. This is a new development building on the idea of determining liquid level by measuring the pressure at the bottom of a liquid container, however it has a number of critical advantages. The system features several FBG-based pressure sensors as described above placed at different depths. Any sensor above the surface of the liquid will read the same ambient pressure. Sensors below the surface of the liquid will read pressures that increase linearly with depth. The position of the liquid surface can therefore be approximately identified as lying between the first sensor to read an above-ambient pressure and the next higher sensor. This level of precision would not in general be sufficient for most liquid level monitoring applications; however a much more precise determination of liquid level can be made by linear regression to the pressure readings from the sub-surface sensors. There are numerous advantages to this multi-sensor approach. First, the use of linear regression using multiple sensors is inherently more accurate than using a single pressure reading to estimate depth. Second, common mode temperature induced wavelength shifts in the individual sensors are automatically compensated. Thirdly, temperature induced changes in the sensor pressure sensitivity are also compensated. Fourthly, the approach provides the possibility to detect and compensate for malfunctioning sensors. Finally, the system is immune to changes in the density of the monitored fluid and even to changes in the effective force of gravity, as might be obtained in an aerospace application. The performance of an individual sensor was characterized and displays a sensitivity (54 pm/cm), enhanced by more than a factor of 2 when compared to a sensor head configuration based on a silica FBG published in the literature, resulting from the much lower elastic modulus of POF. Furthermore, the temperature/humidity behavior and measurement resolution were also studied in detail. The proposed configuration also displays a highly linear response, high resolution and good repeatability. The results suggest the new configuration can be a useful tool in many different applications, such as aircraft fuel monitoring, and biochemical and environmental sensing, where accuracy and stability are fundamental. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Highly sensitive liquid level sensor using a polymer optical Bragg grating for industrial applications

A novel and highly sensitive liquid level sensor based on a polymer optical fiber Bragg grating (POFBG) is reported for the first time. The sensitivity of the sensor is found to be 57 pm/cm of liquid, enhanced by more than a factor of 5 when compared to an equivalent sensor based on silica fiber. © 2015 OSA.

Polymer fibre Bragg gratings and sensing

Polymer FBGs have advantages for sensing because of low Young's modulus, high temperature sensitivity, large strain range and so on. They are attractive for many niche applications such as structural health monitoring of composite materials, biochemical and biomedical sensing. While polymer FBGs have been developed for some time, polymer microfibre Bragg gratings are developed only recently and have shown to introduce some interesting features, e.g. increased pressure sensitivity to pressure / force and improved response time to humidity. We will report and discuss the recent work on polymer FBG and polymer microfibre Bragg gratings as well as their applications such as accelerometer, humidity sensor and force and pressure sensor. © 2015 OSA.

Enhancing the sensitivity of poly(methyl methacrylate) based optical fiber Bragg grating temperature sensors

In poly(methyl methacrylate) (PMMA)-based optical fiber gratings (POFBGs), the temperature response is determined by thermal expansion and the thermo-optic effect of the fiber. Because thermal expansion introduces a positive change and the thermo-optic effect introduces a negative change in the Bragg wavelength of the POFBG, they cancel out each other to some extent, leading to reduced and varying temperature sensitivity. By pre-straining a POFBG, the contribution of thermal expansion can be removed, and, consequently, the temperature sensitivity of POFBG can be greatly enhanced. Theoretical analysis also indicates a reduced thermo-optic coefficient of POFBG due to restrained linear expansion that matches experimental results.

Thermal effects on the photoelastic coefficient of polymer optical fibers

We measure the radial profile of the photoelastic coefficient C(r) in single-mode polymer optical fibers (POFs), and we determine the evolution of C(r) after annealing the fibers at temperatures from 40°C to 80°C. We demonstrate that C(r) in the fibers drawn from a preform without specific thermal pre-treatment changes and converges to values between 1.2 and 1.6×10-12 Pa-1 following annealing at 80°C. The annealed fibers display a smoothened radial profile of C(r) and a lowered residual birefringence. In contrast, the mean value of C(r) of the fiber drawn from a preform that has been pre-annealed remains constant after our annealing process and is significantly higher, i.e., 4×10-12 Pa-1. The annealing process decreases the residual birefringence to a lower extent as well. These measurements indicate the impact of annealing on the thermal stability of the photoelastic coefficient of POFs, which is an essential characteristic in view of developing POF-based thermomechanical sensors.

Investigation and modelling of tremor reducer with the technology of targeted energy transfer

This thesis presents the study of a two-degree-of-freedom (2 DOF) nonlinear system consisting of two grounded linear oscillators coupled to two separate light weight nonlinear energy sinks of an essentially nonlinear stiffness. In this thesis, Targeted Energy Transfer (TET) and NES concept are introduced. Previous studies and research of Energy pumping and NES are presented. The characters in nonlinear energy pumping have been introduced at the start of the thesis. For the aim to design the application of a tremor reduction assessment device, the knowledge of tremor reduction has also been mentioned. Two main parties have been presented in the research: dynamical theoretic method of nonlinear energy pumping study and experiments of nonlinear vibration reduction model. In this thesis, nonlinear energy sink (NES) has been studied and used as a core attachment for the research. A new theoretic method of nonlinear vibration reduction which with two NESs has been attached to a primary system has been designed and tested with the technology of targeted energy transfer. Series connection and parallel connection structure systems have been designed to run the tests. Genetic algorithm has been used and presented in the thesis for searching the fit components. One more experiment has been tested with the final components. The results have been compared to find out most efficiency structure and components for the theoretic model. A tremor reduction experiment has been designed and presented in the thesis. The experiment is for designing an application for reducing human body tremor. By using the theoretic method earlier, the experiment has been designed and tested with a tremor reduction model. The experiment includes several tests, one single NES attached system and two NESs attached systems with different structures. The results of theoretic models and experiment models have been compared. The discussion has been made in the end. At the end of the thesis, some further work has been considered to designing the device of the tremor reduction.

Poly lactic-co-glycolic acid controlled delivery of Disulfiram to target liver cancer stem-like cells

Disulfiram (DS), an anti-alcoholism drug, shows very strong cytotoxicity in many cancer types. However its clinical application in cancer treatment is limited by the very short half-life in the bloodstream. In this study, we developed a poly lactic-co-glycolic acid (PLGA)-encapsulated DS protecting DS from the degradation in the bloodstream. The newly developed DS-PLGA was characterized. The DS-PLGA has very satisfactory encapsulation efficiency, drug-loading content and controlled release rate in vitro. PLGA encapsulation extended the half-life of DS from shorter than 2 minutes to 7 hours in serum. In combination with copper, DS-PLGA significantly inhibited the liver cancer stem cell population. CI-isobologram showed a remarkable synergistic cytotoxicity between DS-PLGA and 5-FU or Sorafenib. It also demonstrated very promising anticancer efficacy and antimetastatic effect in liver cancer mouse model. Both DS and PLGA are FDA approved products for clinical application. Our study may lead to repositioning of DS into liver cancer treatment.

Encapsulation of phase change materials using rice-husk-char

This paper explored a new approach to prepare phase change microcapsules using carbon-based particles via Pickering emulsions for energy storage applications. Rice-husk-char, a by-product in biofuel production, containing 53.58 wt% of carbon was used as a model carbon-based material to encapsulate hexadecane. As a model phase change material, hexadecane was emulsified in aqueous suspensions of rice-husk-char nanoparticles. Water soluble polymers poly(diallyldimethyl-ammonium chloride) and poly(sodium styrene sulfonate) were used to fix the rice-husk-char nanoparticles on the emulsion droplets through layer-by-layer assembly to enhance the structural stability of the microcapsules. The microcapsules formed are composed of a thin shell encompassing a large core consisting of hexadecane. Thermal gravimetrical and differential scanning calorimeter analyses showed the phase change enthalpy of 80.9 kJ kg−1 or 120.0 MJ m−3. Design criteria of phase change microcapsules and preparation considerations were discussed in terms of desired applications. This work demonstrated possible utilisations of biomass-originated carbon-based material for thermal energy recovery and storage applications, which can be a new route of carbon capture and utilisation.

Progress in photosensitive polymer optical fibres and gratings

Polymer optical fibre Bragg gratings are useful for strain sensor applications for large dynamic range. We report recent progress in developing polymer optical fibres with higher photosensitivity and fabricating POF gratings at alternative wavelength. © 2010 Optical Society of America.