Sensores de Bragg para bioaplicações

Doutoramento em FisicaNas últimas décadas, os sensores de Bragg têm sido frequentemente utilizados em inúmeras aplicações, em resultado das características únicas desta tecnologia. Contudo, a comunidade científica tem feito um esforço contínuo em desenvolver sensores que respondam tanto quanto possível aos requisitos e interesses de cada aplicação em particular. As bioaplicações são um campo de crescente interesse pelos sensores de Bragg, atendendo à heterogeneidade e complexidade dos meios de análise em questão. No âmbito desta dissertação foi realizada uma análise teórica dos princípios de funcionamento das redes de Bragg, focada em redes uniformes e inclinadas. Foi também descrito o processo de produção de redes de Bragg regeneradas. Redes de Bragg uniformes foram aplicadas na caracterização da reacção de polimerização e cura de materiais dentários, nomeadamente resina para base de dentadura, cimentos e gessos. Foi feita uma análise comparativa do desempenho de diferentes tipos de cimentos e gessos. Em relação ao gesso foi ainda avaliada a influência do rácio água/pó nas propriedades do material. Devido à importância que o índice de refracção tem na detecção de substâncias, doenças e controlo de qualidade de produtos, foi desenvolvido um sensor de índice de refracção baseado numa rede de Bragg inclinada. Implementaram-se também sensores para medição simultânea de índice de refracção e deformação, índice de refracção e temperatura e índice de refracção, deformação e temperatura, todos baseados numa única rede inclinada. O último dispositivo foi validado em ambiente laboratorial. Com o propósito de desenvolver um sensor baseado em redes de Bragg para monitorização da deformação óssea, foi avaliada a biocompatibilidade da fibra óptica em cultura de células osteoblásticas, e analisada a integridade física e funcionalidade da rede de Bragg nesse meio. O interesse em aumentar a sensibilidade e alargar a gama de trabalho dos sensores conduziu ao revestimento das fibras ópticas. Atendendo ao potencial índole biológica e biomédica do trabalho, usou-se como material de recobrimento o diamante, dada a excelente resposta em termos de biocompatibilidade, resistência à corrosão, não toxicidade e afinidade para espécies químicas e biológicas. Os filmes foram obtidos por deposição química a partir da fase vapor assistida por filamento quente. Para além de amostras de fibra óptica, foram revestidas redes de Bragg uniformes e regeneradas. Os sensores revestidos com diamante foram caracterizados à deformação e à temperatura.In the last decades, Bragg sensors have often been used in numerous applications as a result of the unique features of this technology. However, the scientific community has made an ongoing effort to develop sensors that respond as much as possible to the requirements and interests of each particular application. The bioapplications are a field of growing interest by fiber Bragg sensors due to the heterogeneity and complexity of the media to monitor. As part of this dissertation, a theoretical analysis of the operating principles of Bragg gratings, focused on uniform and tilted gratings was carried out. It was also described the producing method of regenerated Bragg gratings. Uniform FBGs were applied to characterize the polymerization and curing reaction of dental materials, including denture base resin, cements and gypsums. A comparative analysis of the performance of different kinds of cements and gypsums was made. Regarding to gypsum, it has also assessed the influence of the water/powder ratio in the material properties. Due to the importance that the refractive index has in the detection of substances, diseases and quality control of products, a refractive index sensor based on a tilted fiber Bragg grating was developed. Sensors for simultaneous measurement of refractive index and strain, refractive index and temperature and refractive index, strain and temperature, all based on a single tilted grating were also implemented. The last device was validated in the laboratory. Aiming to develop a Bragg grating sensor for measuring strain in bone, the biocompatibility of the optical fiber in osteoblastic cells culture was assessed, and the physical integrity and functionality of the Bragg grating in that medium was evaluated. The interest in improving the sensitivity and extending the working range of the sensors led to the optical fiber coating. Taking into account its biological and biomedical potential applications, the diamond was used as coating material, due to the excellent response in terms of biocompatibility, corrosion resistance, non toxicity and affinity to chemical and biological species. The films were obtained by hot filament chemical vapor deposition. Apart of optical fiber samples, uniform and regenerated Bragg gratings were also coated. The diamond coated sensors were characterized to stain and temperature

Cuspal Displacement Induced by Bulk Fill Resin Composite Polymerization: Biomechanical Evaluation Using Fiber Bragg Grating Sensors

Polymerization shrinkage is a major concern to the clinical success of direct composite resin restorations. The aim of this study was to compare the effect of polymerization shrinkage strain of two resin composites on cuspal movement based on the use of fiber Bragg grating (FBG) sensors. Twenty standardized Class II cavities prepared in upper third molars were allocated into two groups (n=10). Restorations involved the bulk fill placement of conventional microhybrid resin composite (Esthet•X® HD, Dentsply DeTrey) (Group 1) or flowable “low-shrinkage” resin composite (SDR™, Dentsply DeTrey) (Group 2). Two FBG sensors were used per restoration for real-time measurement of cuspal linear deformation and temperature variation. Group comparisons were determined using ANCOVA (α=0.05) considering temperature as the covariate. A statistically significant correlation between cuspal deflection, time, and material was observed (p<0.01). Cuspal deflection reached 8.8 μm (0.23%) and 7.8 μm (0.20%) in Groups 1 and 2, respectively. When used with bulk fill technique, flowable resin composite SDR™ induced significantly less cuspal deflection than the conventional resin composite Esthet•X® HD (p=0.015) and presented a smoother curve slope during the polymerization. FBG sensors appear to be a valid tool for accurate real-time monitoring of cuspal deformation

Fiber Bragg Gratings as e-Health Enablers: An Overview for Gait Analysis Applications

Nowadays, the fast advances in sensing technologies and ubiquitous wireless networking are reflected in medical practice. It provides new healthcare advantages under the scope of e-Health applications, enhancing life quality of citizens. The increase of life expectancy of current population comes with its challenges and growing health risks, which include locomotive problems. Such impairments and its rehabilitation require a close monitoring and continuous evaluation, which add financial burdens on an already overloaded healthcare system. Analysis of body movements and gait pattern can help in the rehabilitation of such problems. These monitoring systems should be noninvasive and comfortable, in order to not jeopardize the mobility and the day-to-day activities of citizens. The use of fiber Bragg gratings (FBGs) as e-Health enablers has presented itself as a new topic to be investigated, exploiting the FBGs’ advantages over its electronic counterparts. Although gait analysis has been widely assessed, the use of FBGs in biomechanics and rehabilitation is recent, with a wide field of applications. This chapter provides a review of the application of FBGs for gait analysis monitoring, namely its use in topics such as the monitoring of plantar pressure, angle, and torsion and its integration in rehabilitation exoskeletons and for prosthetic control

Internal and External Temperature Monitoring of a Li-Ion Battery with Fiber Bragg Grating Sensors

The integration of fiber Bragg grating (FBG) sensors in lithium-ion cells for in-situ and in-operando temperature monitoring is presented herein. The measuring of internal and external temperature variations was performed through four FBG sensors during galvanostatic cycling at C-rates ranging from 1C to 8C. The FBG sensors were placed both outside and inside the cell, located in the center of the electrochemically active area and at the tab-electrode connection. The internal sensors recorded temperature variations of 4.0 ± 0.1°C at 5C and 4.7 ± 0.1° C at 8C at the center of the active area, and 3.9 ± 0.1° C at 5C and 4.0 ± 0.1° C at 8C at the tab-electrode connection, respectively. This study is intended to contribute to detection of a temperature gradient in real time inside a cell, which can determine possible damage in the battery performance when it operates under normal and abnormal operating conditions, as well as to demonstrate the technical feasibility of the integration of in-operando microsensors inside Li-ion cells

A conformação dos ecomuseus: elementos para compreensão e análise

Apresenta uma história dos ecomuseus enraizado nos movimentos de folclore e etnografia regional, do final do século XIX até os dias de hoje, examinando o caso francês. Explora aspectos em geral menos enfatizados neste campo, tal como a natureza e o papel atribuído aos acervos e ao patrimônio cultural e padrões museográticos

Special Issue “Optical Fiber Interferometric Sensors: New Production Methodologies and Novel Applications”

The collection of papers presented in this Special Issue (SI) portraits the state-of-the-art of photonic-based interferometric sensors, where new application areas were explored (such as spirometry) and novel sensitivity limits were achieved, using innovative sensing techniques for the monitoring of parameters, such as displacement, temperature or salinity

Optical Sensors Based on Plastic Fibers

The recent advances of polymer technology allowed the introduction of plastic optical fiber in sensor design. The advantages of optical metrology with plastic optical fiber have attracted the attention of the scientific community, as they allow the development of low-cost or cost competitive systems compared with conventional technologies. In this paper, the current state of the art of plastic optical fiber technology will be reviewed, namely its main characteristics and sensing advantages. Several measurement techniques will be described, with a strong focus on interrogation approaches based on intensity variation in transmission and reflection. The potential applications involving structural health monitoring, medicine, environment and the biological and chemical area are also presented

Optical Fiber Magnetic Field Sensors Based on Magnetic Fluid: A Review

Magnetic field sensing is an important issue for many application areas, such as in the military, industry and navigation. The current sensors used to monitor this parameter can be susceptible to electromagnetic interferences, however due to their advantages over the traditional sensors, the optical fiber devices could be an excellent alternative. Furthermore, magnetic fluid (MF) is a new type of functional material which possesses outstanding properties, including Faraday effect, birefringence, tunable refractive index and field dependent transmission. In this paper, the optical fiber magnetic field sensors using MF as sensing element are reviewed. Due to the extensive literature, only the most used sensing configurations are addressed and discussed, which include optical fiber grating, interferometry, surface plasmon resonance (SPR) and other schemes involving tailored (etched, tapered and U-shaped) fibers

A importância do “festival med” para o desenvolvimento cultural e turístico de Loulé

The cultural and creative tourism is an increasingly important vehicle for economic development of region's attractiveness as a factor that enhances the competitiveness of the destination and in this context the Festival Med is a manifestation of cultural and creative tourism in the Algarve which has allowed the economic development of the town of Loulé and that was the engine of regeneration and rehabilitation of the historic center.The analysis of the studies and other elements that formed the basis of this article shows that the festival is therefore a mean to promote the well-being of residents and visitors, to allow diversifying the local economy, and represents a potential increase in profits for the merchants of the city and the hospitality industry. It diffuses the Mediterranean culture and history, attracts visitors interested in knowledge of the traditions of the nations represented and, moreover, attracts investment to the county.The Festival Med is a focus of tourist attraction in this region of the Algarve and it stands as a project that launches the city's reputation beyond its borders since the script integrates the festivals of "world music" in Europe, having potencial to boost the growing of tourism in the region.O turismo cultural e criativo é cada vez mais um veículo importante para o desenvolvimento económico de uma região, constituindo um factor de atractividade que potencia a competitividade do destino e nesse contexto o festival MED constitui um exemplo de uma manifestação de turismo cultural e criativo no Algarve que tem propiciado o desenvolvimento económico da cidade de Loulé e que foi o motor da regeneração e reabilitação do centro histórico.  Da análise dos estudos e demais elementos que servem de base ao presente artigo resulta que o festival constitui, assim, um meio de promoção do bem-estar dos residentes e visitantes, pois permite diversificar a economia local e representa uma possibilidade de aumento dos lucros para os comerciantes da cidade e para o sector hoteleiro do concelho. Difunde a cultura e a história mediterrânicas, atrai visitantes interessados no conhecimento das tradições das nações representadas e, além do mais, atrai investimento ao concelho.O Festival Med constitui um foco de atracção turística nesta região algarvia e assume-se como um evento que projecta a notoriedade da cidade além-fronteiras, uma vez que já integra o roteiro dos festivais de "world music" da Europa, tendo potencial para dinamizar cada vez mais o turismo na região

Sensor Cell Network for Pressure, Temperature and Position Detection on Wheelchair Users

This work proposes an optical sensing network to monitor pressure and temperature in specific areas of a wheelchair to prevent pressure ulcers and to monitor the position of the wheelchair user by analyzing its pressure distribution. The sensing network is composed of six optical fiber Bragg grating (FBG)-based sensor cells. Each sensor cell is built from a polylactic acid (PLA) base and has two FBGs, one embedded in epoxy resin to monitor pressure variations (FBGP) and another without resin to monitor temperature (FBGT). Once produced, all sensor cells were experimentally characterized for pressure and temperature variations, resulting in an average pressure sensitivity of 81 &plusmn; 5 pm/kPa (FBGP) and &minus;5.0 &plusmn; 0.4 pm/kPa (FBGT), and an average temperature sensitivity of 25 &plusmn; 1 pm/&deg;C (FBGP) and 47.7 &plusmn; 0.7 pm/&deg;C (FBGT). The sensor cells were then placed in six specific areas of a wheelchair (four in the seat area and two in the shoulder blade area) to carry out experimental tests, wherein the response of the sensors to a specific sequence of relief positions was tested. During the execution of the test, the optical signal of all sensors was monitored, in real time, with the pressure and temperature values detected in each zone of the wheelchair. In addition, random position changes were performed in order to evaluate the precision of the proposed sensing network in the identification of such positions