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In recent years, a lot of attention has been directed towards the fabricating of smart structures with embedded optical sensors providing in-situ, non-destructive and real time or on-demand information of the construction structural health.
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... a prototype is designed to be thin and flat in order to provide high elasticity being necessary for easier straining. The prototype design is depicted in Fig. 1. The basic size of the structure is 50x30x3 mm. At the edge of the structure, a small groove is created to show the center. This helps not only to place the grating to the center during the 3D printing, but also to stick or screw the structure correctly on the surface being ...
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... with the groove for the sensor to be placed is printed. Then, printing process is interrupted and fibre with the inscribed FBG is placed into the groove. The FBG sensor is fixed by glue along its length promising better response in the strain during a measurement. In the last step, the final layers that confine the fibre sensor are printed. In Fig. 1, one can observe that the final layers are printed only to confine the fiber sensor and not over the whole surface area. In this way, material consumption and printing time is reduced. Polycarbonate-acrylonitrile butadiene styrene (PC-ABS) is used for 3D printing for the low superior strength, flexibility, as well as good impact and ...
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In this article, a high sensitivity, low temperature-crosstalk strain sensor based on a microsphere embedded Fabry-Perot interferometer (FPI) is reported and experimentally demonstrated. The sensor is fabricated by embedding a microsphere inside a tapered hollow-core fiber (HCF) whose ends are enclosed by two standard single-mode fibers (SMFs). The...
Citations
... For example, when embedded in a thermoplastic polyurethane (TPU) material, a shift of the reflectance spectrum by 136 pm was observed and also a bending sensitivity of about 1.74× compared to bare fiber with a Bragg grating has been demonstrated [31]. However, the encapsulation material itself has a significant effect on the temperature sensitivity, which can increase more than tenfold [27], [28], [32]. ...
Currently, the use of fiber-optic Bragg gratings in biomedical applications, especially in the field of magnetic resonance imaging (MRI), is becoming popular. In these applications, the fiber Bragg grating (FBG) encapsulation plays a crucial role in terms of the accuracy and reproducibility of the measurements. This paper describes in detail the fabrication method of a prototype FBG sensor, which is realized by encapsulating a Bragg grating between two layers of the MR-compatible material Acrylonitrile Butadiene Styrene (ABS) by 3D printing. The sensor thus created, implemented, for example, on the chest of a human body, enables monitoring of the vital functions of the human body. The paper describes the complete procedure for the creation of the prototype sensor, including strain and temperature dependence, as well as results of long-term experimental measurements against the conventional electrocardiography (ECG) standard. Results based on the objective Bland-Altman (B-A) method confirm that the implemented sensor can be used for reliable monitoring of cardiac activity (>95% based on B-A). Taking into account the single fiber optic cable, its simple implementation, its small size and weight < 5g, the presented sensor represents an interesting alternative to conventional ECG.
... Actually, there is a strain distribution along the optical fiber. Thus, it is possible to expect that the force applied is distributed to the adjacent sensors following a beam model [38], where there is a displacement distributed along the fiber with a maximum value at the load application region. of PDMS) was subjected to a force applied in the middle of the LED strip. Figure 3 presents the FEM results of the numerical simulation using the force applied in the sensor system. ...
... Actually, there is a strain distribution along the optical fiber. Thus, it is possible to expect that the force applied is distributed to the adjacent sensors following a beam model [38], where there is a displacement distributed along the fiber with a maximum value at the load application region. Similarly, the strain distributions in the sensor system due to momentums applied around reach axis are presented in Figure 4. ...
This paper presents the development and application of a multiplexed intensity variation-based sensor system for multiplane shape reconstruction. The sensor is based on a polymer optical fiber (POF) with sequential lateral sections coupled with a flexible light-emitting diode (LED) belt. The optical source modulation enables the development of 30 independent sensors using one photodetector, where the sensor system is embedded in polydimethylsiloxane (PDMS) resin in two configurations. Configuration 1 is a continuous PDMS layer applied in the interface between the flexible LED belt and the POF, whereas Configuration 2 comprises a 20 mm length PDMS layer only on each lateral section and LED region. The finite element method (FEM) is employed for the strain distribution evaluation in different conditions, including the strain distribution on the sensor system subjected to momentums in roll, pitch and yaw conditions. The experimental results of pressure application at 30 regions for each configuration indicated a higher sensitivity of Configuration 1 (83.58 a.u./kPa) when compared with Configuration 2 (40.06 a.u./kPa). However, Configuration 2 presented the smallest cross-sensitivity between sequential sensors (0.94 a.u./kPa against 45.5 a.u./kPa of Configuration 1). Then, the possibility of real-time loading condition monitoring and shape reconstruction is evaluated using Configuration 1 subjected to momentums in roll, pitch and yaw, as well as mechanical waves applied on the sensor structure. The strain distribution on the sensor presented the same pattern as the one obtained in the simulations, and the real-time response of each sensor was obtained for each case. In addition, the possibility of real-time loading condition estimation is analyzed using the k-means algorithm (an unsupervised machine learning approach) for the clusterization of data regarding the loading condition. The comparison between the predicted results and the real ones shows a 90.55% success rate. Thus, the proposed sensor device is a feasible alternative for integrated sensing in movement analysis, structural health monitoring submitted to dynamic loading and robotics for the assessment of the robot structure.
... Then, the printing process continues until the printing is finalised [38]. ...
The future vision of advanced manufacturing is one of connected smart manufacturing equipment that takes advantage of data capture and analysis systems to optimise operations. Australia's manufacturing sector is a vital component of the economy. A key to progress is the application of advanced manufacturing technologies, systems and processes. Additive Manufacturing (AM), also known as 3D printing, is an advanced manufacturing technology that plays a significant role in the fourth industrial revolution (Industry 4.0). In recent years, manufacturers in the mining sector have been looking to leverage advanced manufacturing technologies to help improve productivity, efficiency and safety. Gravity Separation Spirals (GSS) are vital to mineral processing operations in the mining sector for separating mineral-rich slurry into its different density components, particularly when high throughput is required. GSS have traditionally been manufactured in moulds, using a manual process that is subject to numerous inherent drawbacks, including significant tooling costs, limited customisation, and the risk of worker exposure to hazardous materials. A multi-partner project is underway to develop a bespoke 3D printer to print an upgraded and customisable GSS. By embedding Internet of Things sensors inside the GSS, it is possible to remotely determine the operation conditions, perform predictive maintenance, and use the collected data to optimise the production output. The research in this thesis is focused on developing the required sensors that can be embedded in the printed spiral. These sensors can be either 3D printed or conventional sensors. Research also focuses on the sensor placement problem to determine the ideal location to place sensors so as to maximise the information gain whilst simultaneously considering the 3D printing process, and the required structural integrity. In order to print the structure with the sensors inline, a novel radial slicing algorithm has been devised to slice helical objects, along with a path planning algorithm for radial robot-based 3D printing. Experiments using conductive filament have shown how the devised 3D printed sensors can be used to measure, with acceptable accuracy, the required physical quantities, such as strain, temperature, and vibration. The design of the traditional 3D strain sensor has been improved to compensate for temperature changes. A partial pipe flow meter has been developed based on ultrasonic velocity measurement and capacitance level sensing. Experimental results showed that this sensor performed better than a conventional flow meter. The devised voxel-based sensor placement approach has been shown to propose ideal locations that consider various competing objectives.
... Recently, concurrently with the 3D printing spreading, FBGs have been embedded also in different kind of 3Dprinted structures [15]- [19]. Principally they have been proposed for structural strain [20], temperature [21] and strain monitoring [22]. Another study developed an hydrostatic pressure sensor by embedding an FBG inside a 3D printed ABS (acrylonitrile butadiene styrene) structure [23]. ...
... This method ensures a direct strain transfer between the 3D printed material and the fiber, which however is inhomogeneous, with a periodicity determined by the filling density and other design parameters. Therefore, in some cases the use of an intermediary adhesive layer made of epoxy resin or similar adhesives is the preferred choice [18]. Referring to the analytical model developed by the authors in a recent study [19], the strain transfer efficiency, which can be summarized with the shear lag constant value, should decrease due to the presence of the additional layer. ...
The use of optical fiber sensors (OFS) has spread in the Structural Health Monitoring (SHM) community for their ability to detect many different physical quantities, robustness against electromagnetic disturbances, light weight and embedding possibilities. The last point has been widely investigated for different types of materials, but only recently researchers considered the possibility to embed optical fibers in 3D printed structures. Additive Manufacturing (AM) offers new opportunities in terms of design, for the manufacturing of structures with complex geometries in a relatively low amount of time. However, new challenges must be considered, including innovative embedding solutions for different types of sensors. As a first step, this work discusses current embedding strategies for optical fiber sensors in structures produced with the Fused Deposition Modeling (FDM) technique. A novel methodology to embed OFS is introduced and then tested through the production of specimens at three different filling densities and six different loads. The experimental results, where both distributed OFS and strain gauges were used, were also compared with the data obtained from a numerical model developed in Abaqus/CAE in which the filling pattern of the specimens was accurately reproduced. Finally, the results were critically discussed, highlighting both agreements and discrepancies with respect to the expected data.
... In recent years, concurrently with the widespread of 3Dprinting, FBGs have been embedded also in 3D-printing structures [12]- [15]. Principally they have been proposed for structural strain [16], temperature [17], pressure [18] and strain monitoring [19]. These studies take also into account the properties of the materials used for the printing [17], the infilling density [20] and the effect of the temperature strain cross sensitivities [13]. ...
Aim of this work is the analysis of the 3D printed patches embedding fiber Bragg gratings (FBGs) for deformation monitoring. In particular, the paper first describes the manufacturing process and the performances of FBGs embedded in PLA and ABS rectangular patches, showing that the sensitivity to temperature is strongly dependent on the material and on the dimension of the patches. Then, the deformation characteristics are, for the first time, explored showing that the thickness of the patch, influencing the neutral axis position, acts as gaining factor on the deformation sensitivity of the FBG sensor. Such results enable the application of FBG embedded in 3D-printed patches for deformation monitoring taking in proper consideration the dimension of the patches, in particular its thickness, that allows to enhance the wavelength shift of the applied FBG sensors.
... Concurrently with the wide spreading of 3D-printing, in recent years, FBGs have been embedded in 3D-printed structures [18], principally for structural strain [19], temperature [20], pressure [21] and strain monitoring [22], [23] applications. Properties of the materials used for the printing [20], the filling density [24] and the effect of the temperature strain cross sensitivities are also considered in these studies. ...
... 22 FBG sensors were embedded in a 3D printed sensor structure for mechanical strain measurements. 23 FBG sensors were used for quasidistributed dynamic strain measurement and strain modal analysis of hydraulic system pipelines. 24,25 Embedded FBGs were used to monitor strain in aluminium alloys during production. ...
Multi-point forming uses forces applied to a tool, comprising of multiple pins set at different heights, to form sheet metal for panelling in white goods, automotive bodywork, aircraft frames and so on. The use of multiple pins allows for rapid change over and flexibility in the tool making it suitable for small-batch and prototype component manufacture. To explore the relationship between ‘springback’ of the sheet metal on release from the tool, and the applied pin force, it is first necessary to understand and measure the forming forces. This article presents a novel method of measuring forming forces on individual pins in a multi-point forming tool using fibre Bragg grating sensors, monitoring the elastic strain on the selected pins during the forming process. The operating principles behind forming force measurements using fibre Bragg gratings are introduced and a relationship is developed between springback in the formed part after the final unloading and the forming force as measured on selected individual pins under different compression ratios (30%, 40%, 50% and 60%) of the elastic cushion between the tips of the pins and the workpiece. Experiments were performed to validate the proposed measuring method, and results indicate that forming forces detected by the proposed method correlated well with the results obtained by numerical simulation. This suggests the proposed method has good potential for real-time measurement and monitoring of forming force distribution in multi-point forming tools during the forming process.
... Another important advantage of optical fiber sensors is their ability to be embedded in different structures (rigid and flexible). Thus, FBG sensors are already embedded in 3D-printed structures [30][31][32] and it is possible to foresee the 3D printing technology as the link between the FBG-based sensors and the soft robotics devices. In this way, the soft robotic device can be fabricated using 3D printing (as previously shown in [7]) with an embedded FBG-based sensor system for measuring different parameters. ...
This paper presents the development of temperature sensors based on fiber Bragg gratings (FBGs) embedded in 3D-printed structures made of different materials, namely polylatic acid (PLA) and thermoplastic polyurethane (TPU). A numerical analysis of the material behavior and its interaction with the FBG sensor was performed through the finite element method. A simple, fast and prone to automation process is presented for the FBG embedment in both PLA and TPU structures. The temperature tests were made using both PLA- and TPU-embedded FBGs as well as an unembedded FBG as reference. Results show an outstanding temperature sensitivity of 139 pm/°C for the FBG-embedded PLA structure, which is one of the highest temperature sensitivities reported for FBG-based temperature sensors in silica fibers. The sensor also shows almost negligible hysteresis (highest hysteresis below 0.5%). In addition, both PLA- and TPU-embedded structures present high linearity and response time below 2 s. The results presented in this work not only demonstrate the feasibility of developing fully embedded temperature sensors with high resolution and in compliance with soft robot application requirements, but also show that the FBG embedment in such structures is capable of enhancing the sensor performance.
This comprehensive review delves into the rapidly evolving landscape of material extrusion-based 3D printing techniques for sensor fabrication, with a specific focus on fused filament fabrication (FFF) and direct ink write (DIW) methods also known as robocasting. Employing a scoping review methodology, the study addresses the fundamental question of the current state of knowledge in additive manufacturing of sensors using these two 3D printing approaches. The paper focuses on the detailed investigation involving diverse sensor types, challenges, sensor characteristics, and materials utilized in the fabrication process. The methodology encompasses five stages, from formulating the research question to an extensive discussion, including database searches and the establishment of inclusion and exclusion criteria. The ensuing discussion meticulously dissects FFF and DIW methodologies, elucidating advancements, challenges, and limitations across a spectrum of sensors. The total of 68 sensors fabricated by the above-mentioned techniques has been discussed. The FFF section scrutinizes strain sensors, accelerometers, acoustic emission sensors, electrochemical sensors, and more, while the DIW section provides insights into strain sensors, pressure sensors, temperature sensors, electrochemical sensors, humidity sensors, antennas, and pulse sensors. The review concludes with a reflective analysis of significant challenges inherent in DIW-printed and FFF-printed sensors, offering a robust and insightful resource that charts the course for future breakthroughs in material extrusion-based 3D printing of sensors.
