Dissertations / Theses on the topic 'QCM sensors'

The Quartz crystal microbalance (QCM) is a very sensitive mass-detecting device which is based on changes in to the vibrational frequency of quartz crystals after adsorption of substances to a modified crystal surface. In this study a QCM-based biosensor was developed for the rapid diagnosis of influenza viruses and its suitability and limitations were compared with currently available diagnostic methods on 67 clinical samples (nasal washes) received during the 2005 Australian winter. The type-specific and conserved viral M1 proteins of both A/PR/8/34 and B/Lee/40 viruses were used to prepare polyclonal antisera for the development of an ELISA. The limits of detection of ELISAs for the detection of purified A/PR/8/34 and B/Lee/40 ƒnviruses were 20ƒÝg/mL ƒnand 14 ƒÝg/mL using polyclonal antibodies, and 30 ƒÝg/mL and 20 ƒÝg/mL for monoclonal antibodies, respectively. The limit for detection of each virus was 104 pfu/mL, irrespective of whether antisera or monoclonal antibodies were used for capture. Non-purified cell culture-grown preparations of either virus could be detected at 103 pfu/mL The QCM utilised the same reagents used in ELISAs. However, a number of parameters were then further optimised to improve the sensitivity of the tests. These included blocking of non-specific binding, examination of the effects of flow-cell compression, the role of pH, flow rate, antibody concentration and the addition of protein A to the crystal surfaces of the biosensor. The lowest virus concentration that could be detected with the QCM was 104 pfu/mL for egg-grown preparations of both A/PR/8/34 and B/Lee/40, which could be detected within 30 min. However, conjugation of 13 nm gold nanoparticles to a second detector antibody resulted in a 10-fold increase in sensitivity and a detection limit of 103 pfu/mL that could be determined within 1 h. The direct detection of the influenza viruses in nasal samples was not possible by QCM because of the significant frequency fluctuation that was probably caused by the viscosity of the samples. Therefore, an additional culture step of 12 h was required, which increased the processing time to 2 days. The QCM/nanoparticle method was shown to be as sensitive as the standard cell culture method, and the QCM method as sensitive as the shell vial method. The QCM and QCM/nanoparticle methods were shown to be 81 and 87% as sensitive and both were 100% as specific as the real-time polymerase chain reaction. However, for use in rapid diagnosis, improvements are required to remove frequency fluctuation resulting from the direct use of nasal samples.

MEMS (Microelectromechanical Systems) acoustic sensors are a promising platform for Point-of-Care biosensing. In particular, piezoelectrically driven acoustic sensors can provide fast results with high sensitivity, can be miniaturized and mass produced, and have the potential to be fully integrated with sample handling and electronics in handheld devices. Furthermore, they can be designed as multiplexed arrays to detect multiple biomarkers of interest in parallel. In order to develop a microfabricated biosensing platform, a specific and high affinity biodetection platform must be optimized, and the microfabricated sensors must be designed to have high sensitivity and maintain good performance in a liquid environment. A biomolecular sensing system that uses high affinity peptide aptamers and a passivation layer has been optimized for the detection of proteins of interest using the quartz crystal microbalance with dissipation monitoring (QCM-D). The resulting system is highly specific to target proteins, differentiating between target IgG molecules and other closely related IgG subclasses, even in complex environments such as serum. Piezoelectrically actuated MEMS resonators are designed to operate in flexural microplate modes, with several modes shown to be ideally suited for fluid based biosensing due to improved performance in the liquid environment. The increase in quality factor of these MEMS microplate devices in liquid, as compared to air, is further investigated through the analytical and finite element modeling of MEMS fluid damping mechanisms, with a focus on acoustic radiation losses for circular microplate devices. It is found that the impedance mismatch at the air-water interface of a droplet is a key contributor to reduced acoustic radiation losses and thus improved device performance in water. Microplate acoustic sensors operating in flexural plate wave and microplate flexural modes are then integrated with a fluidic cell to facilitate protein sensing from fluid samples. Flexural plate wave devices are used to measure protein mass adsorbed to the sensor surface and initial results toward microplate flexural mode protein sensing are presented. Finally, challenges and areas of future research are discussed to outline the path towards finalization of a sensing platform taking advantage of the combination of the sensitive MEMS acoustic sensor capable of operating in a liquid environment and the specific and high affinity biomolecular detection system. Together, these form the potential basis of a novel Point-of-Care platform for simple and rapid monitoring of protein levels in complex samples.

The object of this thesis research is to facilitate the appraisal and analysis of the signatures of the modern acoustic wave biosensors, as well as to improve the experimental methodology to enhance sensor performance. For this purpose, both theoretical characterization of acoustic wave sensor signatures and experimental studies for the most frequently used acoustic wave biosensors, the liquid phase QCM (quartz crystal microbalance) and the vapor phase SAW (surface acoustic wave) sensors, are presented. For the study of SAW vapor phase detection, the author fabricated different types of two-port SAW resonator sensors on quartz substrates and designed and performed a significant number of detection experiments. These were conducted both with calibrated or known target samples under laboratory conditions at Georgia Tech Hunt Lab and with samples of unknown concentrations such as seized crack cocaine (courtesy of Georgia Bureau of Investigation, GBI) to see the sensors capability to work in the field conditions. In addition, the dependence of the SAW sensor signatures on specific locations of the surface perturbation was investigated to account for some observed abnormal responses. Finally, a novel approach to classify and visualize chemically analogous substances is introduced. The author expects that the thesis work herein may contribute to the study of the modern acoustic wave biosensors which includes but is not limited to: the establishment of underpinning theory that will aid in the evaluation of the signatures; the practical aspects of design and fabrication of SAW devices specific to the vapor phase immunoassay; the development of efficient experimental methodologies; the strategic immobilization of a biolayer on SAW resonator based biosensors; and, the acquisition of reference data for the development of commercial acoustic wave sensors.

For centuries scientific ingenuity and innovation have been influenced by Mother Natures perfect design. One of her more elusive designs is that of the sensory olfactory system, an array of highly sensitive receptors responsible for chemical vapor recognition. In the animal kingdom this ability is magnified among canines where ppt (parts per trillion) sensitivity values have been reported. Today, detection dogs are considered an essential part of the US drug and explosives detection schemes. However, growing concerns about their susceptibility to extraneous odors have inspired the development of highly sensitive analytical detection tools or biosensors known as electronic noses. In general, biosensors are distinguished from chemical sensors in that they use an entity of biological origin (e.g. antibody, cell, enzyme) immobilized onto a surface as the chemically-sensitive film on the device. The colloquial view is that the term biosensors refers to devices which detect the presence of entities of biological origin, such as proteins or single-stranded DNA and that this detection must take place in a liquid. Our biosensor utilizes biomolecules, specifically IgG monoclonal antibodies, to achieve molecular recognition of relatively small molecules in the vapor phase.

[EN] Different electronic interfaces have been proposed to measure major parameters for the characterization of quartz crystal microbalance (QCM) during the last two decades. The measurement of the adequate parameters of the sensor for a specific application is very important, since an error in this measure can lead to an error in the interpretation of the results. The requirements of the system of characterization depend on the application. In this thesis we propose two characterization systems for two types of applications that involve the majority of sensor applications: 1) Characterization of materials under variable damping conditions and 2) Detection of substances with high measurement resolution. The proposed systems seek to solve the problems detected in the systems currently in use. For applications in which the sensor damping varies during the experiment, we propose a system based on a new configuration of the technique of automatic capacitance compensation (ACC). This new configuration provides the measure of the series resonance frequency, the motional resistance and the parallel capacitance of the sensor. Moreover, it allows an easy calibration of the system that improves the precision in the measurement. We show the experimental results for 9 and 10 MHz crystals in fluid media, with different capacitances in parallel, showing the effectiveness in the capacitance compensation. The system presents some deviation in frequency with respect to the series resonance frequency, as measured with an impedance analyser. These deviations are due to the non-ideal, specific behaviour of some of the components of the circuit. A new circuit is proposed as a possible solution to this problem. For high-resolution applications we propose an integrated platform to characterize high-frequency acoustic sensors. The proposed system is based on a new concept in which the sensor is interrogated by means of a very stable, low-noise external source at a constant frequency, while the changes provoked by the charge in the phase of the sensor are monitored. The use of high-frequency sensors enhances the sensitivity of the measure, whereas the design characterization system reduces the noise in the measurement. The result is an improvement in the limit of detection (LOD). This way, we achieve one of the challenges in the acoustic high-frequency devices. The validation of the platform is performed by means of an immunosensor based in high fundamental frequency QCM crystals (HFF-QCM) for the detection of two pesticides: carbaryl and thiabendazole. The results obtained for carbaryl are compared to the results obtained by another high-frequency acoustic technology based in Love sensors, with the optical technique based in surface plasmonic resonance and with the gold standard technique Enzyme Linked Immunoassay (ELISA). The LOD obtained with the acoustic sensors HFF-QCM and Love is similar to the one obtained with ELISA and improves by one order of magnitude the LOD obtained with SPR. The conceptual ease of the proposed system, its low cost and the possibility of miniaturization of the quartz resonator, allows the characterization of multiple sensors integrated in an array configuration, which will allow in the future to achieve the challenge of multianalyte detection for applications of High-Throughput Screening (HTS).
[ES] Durante las dos últimas décadas se han propuesto diferentes interfaces electrónicos para medir los parámetros más importantes de caracterización de los cristales de microbalanza de cuarzo (QCM). La medida de los parámetros adecuados del sensor para una aplicación específica es muy importante, ya que un error en la medida de dichos parámetros puede resultar en un error en la interpretación de los resultados. Los requerimientos del sistema de caracterización dependen de la aplicación. En esta tesis se proponen dos sistemas de caracterización para dos ámbitos de aplicación que comprenden la mayoría de las aplicaciones con sensores QCM: 1) Caracterización de materiales bajo condiciones de amortiguamiento variable y 2) detección de sustancias con alta resolución de medida. Los sistemas propuestos tratan de resolver la problemática detectada en los ya existentes. Para aplicaciones en las que el amortiguamiento del sensor varía durante el experimento, se propone un sistema basado en una nueva configuración de la técnica de compensación automática de capacidad (ACC). La nueva configuración proporciona la medida de la frecuencia de resonancia serie, la resistencia dinámica y la capacidad paralelo del sensor. Además, permite una fácil calibración del sistema que mejora la precisión en la medida. Se presentan resultados experimentales para cristales de 9 y 10MHz en medios fluidos, con diferentes capacidades en paralelo, demostrando la efectividad de la compensación de capacidad. El sistema presenta alguna desviación en frecuencia con respecto a la frecuencia resonancia serie, medida con un analizador de impedancias. Estas desviaciones son explicadas convenientemente, debidas al comportamiento no ideal específico de algunoscomponentes del circuito. Una nueva propuesta de circuito se presenta como posible solución a este problema. Para aplicaciones de alta resolución se propone una plataforma integrada para caracterizar sensores acústicos de alta frecuencia. El sistema propuesto se basa en un nuevo concepto en el que el sensor es interrogado, mediante una fuente externa muy estable y de muy bajo ruido, a una frecuencia constante mientras se monitorizan los cambios producidos por la carga en la fase del sensor. El uso de sensores de alta frecuencia aumenta la sensibilidad de la medida, por otro lado, el sistema de caracterización diseñado reduce el ruido en la misma. El resultado es una mejora del límite de detección (LOD). Se consigue con ello uno de los retos pendientes en los dispositivos acústicos de alta frecuencia. La validación de la plataforma desarrollada se realiza con una aplicación de un inmunosensor basado en cristales QCM de alta frecuencia fundamental (HFF-QCM) para la detección de dos pesticidas: carbaryl y tiabendazol. Los resultados obtenidos para el Carbaryl se comparan con los obtenidos con otra tecnología acústica de alta frecuencia basada en sensores Love, con la técnica óptica basada resonancia superficial de plasmones (SPR) y con la técnica de referencia Enzyme Linked Immuno Assay (ELISA). El LOD obtenido con los sensores acústicos HFFQCM y Love es similar al obtenido con las técnicas ELISA y mejora en un orden de magnitud al obtenido con SPR. La sencillez conceptual del sistema propuesto junto con su bajo coste, así como la capacidad de miniaturización del resonador de cuarzo hace posible la caracterización de múltiples sensores integrados en una configuración en array, esto permitirá en un futuro alcanzar el reto de la detección multianalito para aplicaciones High-Throughput Screening (HTS).
[CAT] Durant les dues últimes dècades s'han proposat diferents interfases electrònics per a mesurar els paràmetres més importants de caracterització dels cristalls de microbalança de quars (QCM). La mesura dels paràmetres adequats del sensor per a una aplicació específica és molt important, perquè un error en la interpretació dels resultats pot resultar en un error en la interpretació dels resultats. Els requeriments del sistema de caracterització depenen de l'aplicació. En aquesta tesi, es proposen dos sistemes de caracterització per a dos àmbits d'aplicació que comprenen la majoria de les aplicacions amb sensors QCM: 1) Caracterització de materials sota condicions d'amortiment variable i 2) detecció de substàncies amb alta resolució de mesura. Els sistemes proposats tracten de resoldre la problemàtica detectada en els ja existents. Per a aplicacions en les quals l'amortiment del sensor varia durant l'experiment, es proposa un sistema basat en una nova configuració de la tècnica de compensació automàtica de capacitat (ACC). La nova configuració proporciona la mesura de la freqüència de ressonància sèrie, la resistència dinàmica i la capacitat paral¿lel del sensor. A més, permet un calibratge fàcil del sistema que millora la precisió de la mesura. Es presenten els resultats experimentals per a cristalls de 9 i 10 MHz en mitjans fluids, amb diferents capacitats en paral¿lel, demostrant l'efectivitat de la compensació de capacitat. El sistema presenta alguna desviació en freqüència respecte a la freqüència ressonància sèrie, mesurada amb un analitzador d'impedàncies. Aquestes desviacions són explicades convenientment, degudes al comportament no ideal específic d'alguns components del circuit. Una nova proposta de circuit es presenta com a possible solució a aquest problema. Per a aplicacions d'alta resolució es proposa una plataforma integrada per a caracteritzar sensors acústics d'alta freqüència. El sistema proposat es basa en un nou concepte en el qual el sensor és interrogat mitjançant una font externa molt estable i de molt baix soroll, a una freqüència constant mentre es monitoritzen els canvis produïts per la càrrega en la fase del sensor. L'ús de sensors d'alta freqüència augmenta la sensibilitat de la mesura, per altra banda, el sistema de caracterització dissenyat redueix el soroll en la mateixa. El resultat és una millora en el límit de detecció (LOD). S'aconsegueix amb això un dels reptes pendents en els dispositius acústics d'alta freqüència. La validació de la plataforma desenvolupada es realitza amb una aplicació d'un immunosensor basat en cristalls QCM d'alta freqüència fonamental (HFF-QCM) per a la detecció de dos pesticides: carbaryl i tiabendazol. Els resultats obtinguts per al carbaryl es comparen amb els obtinguts amb altra tecnologia acústica d'alta freqüència basada en sensors Love, amb la tècnica òptica basada en ressonància superficial de plasmons (SPR) i amb la tècnica de referència Enzyme Linked Immuno Assay (ELISA). El LOD obtingut amb els sensors acústics HFF-QCM i Love és similar al obtingut amb les tècniques ELISA i millora en un ordre de magnitud el obtingut amb SPR. La senzillesa conceptual del sistema proposat junt amb el seu baix cost, així com la capacitat de miniaturització del ressonador de quars fa possible la caracterització de múltiples sensors integrats en una configuració en array, el que permetrà en un futur assolir el repte de la detecció multianalit per a aplicacions High-Throughput Screening (HTS).
García Narbón, JV. (2016). Improved characterization systems for quartz crystal microbalance sensors: parallel capacitance compensation for variable damping conditions and integrated platform for high frequency sensors in high resolution applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63249
TESIS

In this study, gas sensing systems that are based on piezoelectric smart material and structures are proposed, designed, developed, and tested, which are mainly aimed to address the temperature dependent CO2 gas sensing in a real environment. The state-of-the-art of gas sensing technologies are firstly reviewed and discussed for their pros and cons. The adsorption mechanisms including physisorption and chemisorption are subsequently investigated to characterize and provide solutions to various gas sensors. Particularly, a QCM based gas sensor and a C-axis inclined zigzag ZnO FBAR gas sensor are designed and analyzed for their performance on room temperature CO2 gas sensing, which fall into the scope of physisorption. In contrast, a Langasite (LGS) surface acoustic wave (SAW) based acetone vapor sensor is designed, developed, and tested, which is based on the chemisorption analysis of the LGS substrate. Moreover, solid state gas sensors are characterized and analyzed for chemisorption-based sensitive sensing thin film development, which can be further applied to piezoelectric-based gas sensors (i.e. Ca doped ZnO LGS SAW gas sensors) for performance enhanced CO2 gas sensing. Additionally, an innovative MEMS micro cantilever beam is proposed based on the LGS nanofabrication, which can be potentially applied for gas sensing, when combined with ZnO nanorods deposition. Principal component analysis (PCA) is employed for cross-sensitivity analysis, by which high temperature gas sensing in a real environment can be achieved. The proposed gas sensing systems are designated to work in a high temperature environment by taking advantage of the high temperature stability of the piezoelectric substrates.

La détection de gaz est un enjeu de plus en plus important, aussi bien dans le domaine de la surveillance de la qualité de l’air -intérieur et extérieur- que dans le suivi de procédés. Cet enjeu est d’autant plus critique dans le cas des composés organiques volatiles (COVs) que leur impact sur la santé publique est avéré. Détecter et quantifier leur présence devient une problématique majeure et différentes solutions existent. L’une d’elles, basée sur le couplage d’une nano-poutre résonnante et d’une micro colonne de chromatographie, s’avère être une solution prometteuse. Ces deux dispositifs alliant sélectivité et grande sensibilité nécessitent cependant une fonctionnalisation à l’aide d’une couche sensible. Ces travaux se sont focalisés sur le développement de matériaux sensibles de la famille des SiOCH déposés en couche mince par dépôt chimique en phase vapeur assisté par plasma (PECVD). L’étude de la réponse sous gaz des différents matériaux synthétisés au cours de cette thèse a été réalisée à l’aide de microbalances à cristal de quartz (QCM). Les mesures obtenues ont ensuite été corrélées à un modèle simple permettant de proposer une interprétation de l’interaction entre les SiOCH et le gaz d’intérêt, à l’équilibre mais aussi en régime dépendant du temps. La première partie de l’étude montre l’impact de la composition chimique de ces matériaux sur leur affinité envers un gaz représentatif des COVs aromatiques : le toluène. En s’appuyant sur des caractérisations physico-chimiques, le rôle de différentes liaisons chimiques ainsi que celui de l’hydrophobie des couches minces sur l’interaction avec le gaz d’intérêt a été analysé. Ces travaux montrent qu’un compromis entre composition chimique et hydrophobie doit être trouvé afin de préserver affinité et temps de réponse des SiOCH. L’étude de l’influence de la porosité sur la sensibilité a ensuite été abordée dans un second temps. Pour cela, des procédés originaux de réalisation de couches minces poreuses ont été développés afin de proposer de nouveaux matériaux poreux et d’accroître leur sensibilité vis-à-vis du toluène. Les limites de l’approche soustractive généralement utilisée pour ce type de matériau (i.e. l’approche porogène) ont pu ainsi être dépassées en termes de porosité et de tailles de pores. Concernant la détection de gaz, il s’avère difficile de décorréler l’impact de la chimie de celui de la porosité. Quoi qu’il en soit, l’augmentation de la porosité ouverte n’apparait pas comme le seul paramètre pertinent pour accroître la sensibilité de ces matériaux aux faibles concentrations
Gas detection is a growing field, both for indoor and outdoor air quality monitoring and for process monitoring. It is indeed particularly critical in the case of volatile organic compounds (VOC) whose impact on public health is proven. Detecting and quantifying their presence becomes a major problem and various solutions are available. One of them, based on the coupling of a resonant beam and a chromatography micro column, appears to be a promising solution. Those two devices combine selectivity and high sensitivity; however, they require functionalization with a sensitive layer. This work focused on SiOCH thin films deposited by PECVD. The gas interaction of the sensitive layers deposited during this work was studied using quartz crystal microbalances (QCM). The obtained measurements were then correlated to a simple model, providing an interpretation of the interaction – for steady-state but also kinetic regime - between the SiOCH and the gas of interest. The first part of the study shows the impact of the chemical composition of those materials on their affinity for toluene, representative for aromatic VOCs. Relying on physico-chemical characterization techniques, the role of various chemical bonds on the solid/gas interaction was investigated. This work shows that a compromise between chemical composition and hydrophobicity has to be reached to preserve SiOCH affinity and temporal response. The influence of porosity was then explored in a second step to further increase the sensitivity of those materials. Original deposition processes were developed in order to propose new porous materials with higher toluene affinity. The limits of the subtractive approach generally used for these PECVD materials (i.e. the porogen approach) were then overcome in terms of porosity and pore size. Concerning gas detection, it is difficult to decorrelate between the impact of chemistry and porosity. Whatever, increasing porosity does not appear to be the only relevant parameter in order to increase these materials affinity at low concentrations

Résumé indisponible
This PhD work is dedicated to investigate potentialities of phthalocyanines materials to realize a Quartz Crystal Microbalance (QCM) sensor for Benzene, Toluene and Xylenes (BTX) detection in air. The goal is to develop a sensor-microsystem capable of measuring BTX concentrations quantitatively below the environmental guidelines with sufficient accuracy. To achieve these objectives, our strategies mainly focused on experimental works encompassing sensors realization, sensing material characterizations, development of gas-testing facility and sensor testing for different target gases. One of the main aims is to identify most appropriate phthalocyanine material for sensor development. After comparative sensing studies, tert-butyl-copper phthalocyanine based QCM device is found as most sensitive and detail metrological characteristics are further investigated. Results show repeatable, reversible and high magnitude of response, low response and recovery times, sub-ppm range detection limit, high resolutions and combined selectivity of BTX gases among common atmospheric pollutants. Special focus is given to understand the gas/material interactions which are achieved by (a) XRD and SEM characterizations of sensing layers, (b) formalization of a two-step adsorption model and (c) assessing extent of diffusion of target gas in sensing layer. At last, possible ageing of sensor and suitable storage conditions to prevent such effect are investigated

I augusti 2007 tillfrågades författaren av Attana AB om han kunde konstruera dennes QCM-sensorchip för formsprutning som en del av hans examensarbete inom industriell design. Examensarbetet innefattade de två plastdelarna som utgör hölget av sensorchipet. Ytterliggare skulle en ny konstruktionslösning som underlättar montering av sensorchipet föreslås, en given plats för identifikationsmärkning av sensorchipet skulle implementeras och den estetiska aspekten av designen skulle slutföras inom ramarna av arbetet. Arbetsprocessen innebar ett tvärdisciplinärt uppdrag som ingenjör, designer och projektledare i nära samarbete med andra utvecklings- och tillverkningsingenjörer, materialspecialister och biokemister. Arbetet fortskred iterativt genom fyra faser, nämligen: förstudie, analys, syntes och utvärdering. Arbetet resulterade i en förenklad monteringskonstruktion och en integrerad plats för identifikationsmärkning av chipet. Designen och konstruktionen var också till en viss gräns verifierade med hänsyn till generiska riktlinjer för formsprutning och av specialister som undersökte konstruktionslösningen. En konstruktionslösning där ett snäppfäste integrerades för att underlätta montering av delarna presenterades av författaren. Dessutom presenterades ett urval av lämpliga material. I framtida arbete måste formsprutningsverktygsmakaren slutföra nödvändiga beräkningar för att tillåta eftersökta toleranser i det formsprutade sensorchipet.
In August 2007 the author was asked by Attana AB to construct its QCM sensor chip for injection molding as part of his Master Thesis in Industrial Design Engineering. The thesis work concerned the plastic housing of the sensor chip which consists of two plastic parts. In addition, a new construction solution that simplified assembly was to be proposed, a designated area for identification tagging was to be integrated into the design, and the aesthetic aspect of the design was to be finalized. The process implied working cross-disciplinary as an engineer, designer and a project manager in close collaboration with other development engineers, manufacturing engineers, material specialists and biochemists. The work iteratively progressed through the four phases: research, analysis, synthesis and evaluation. The work resulted in simplified assembly construction and the integration of a designated feature for identification-tagging. The design and construction were also verified, to a certain extent, respective of generic guidelines for injection molding and from specialists who reviewed the construction. A construction solution was proposed with an integrated snap fit design to allow simplified assembly. A selection of materials was also presented. Further investigation has to be done on behalf of the mold tool manufacturer in order to finalize the construction and with respect to tolerances.

 

Control of protein immobilization at sensor surfaces is of great interest within various scientific fields, since it enables studies of specific biomolecular interactions. To achieve this, one must be able to immobilize proteins with retained native structure, while minimizing non-specific protein binding. The high affinity interaction between streptavidin (SA) and biotin is extensively used as a linker between a surface, where SA is immobilized, and the (biotinylated) molecule of interest. Self- assembled monolayers (SAMs) of poly- and oligo ethylene glycol (PEG and OEG) derivatives have been proven in literature to minimize non-specific protein binding, and biotin-exposing SAMs have been shown efficient for immobilization of SA.

The aim of this master's thesis project was to develop biotinylated gold surfaces for quartz crystal microbalance with dissipation monitoring (QCM-D) applications through the self-assembly of mixed monolayers of thiolated OEG (or PEG) derivatives with or without a terminal biotin head group. For this, different thiol compounds were to be compared and evaluated. For the systems under study, the required biotin density for maximum specific SA immobilization was to be established, while keeping the non-specific serum adsorption at a minimum. Model experiments with biotinylated proteins immobilized to the SA-functionalized surfaces were to be performed to evaluate the possibilities for commercialization.

A protocol for the preparation of a novel biotinylated surface was developed based on the immersion of gold substrates in an ethanolic incubation solution of dithiols with OEG chains (SS-OEG and SS-OEG-biotin, 99:1) and found to give reproducible results with respect to low non-specific protein binding and immobilization of a monolayer of SA. The modified surfaces allowed for subsequent immobilization of biotinylated bovine serum albumin (bBSA) and biotinylated plasminogen (bPLG). PLG was the subject of a challenging case study, using a combination of QCM-D and surface plasmon resonance (SPR), where the immobilized protein was subjected to low molecular weight ligands that were believed to induce conformational changes. The high control of the surface chemistry allowed for the interpretation of the increased dissipation shift upon ligand binding in terms of conformational changes.

An obstacle before commercialization of the described biotinylated surfaces is that they do not seem stable for storage > 7 days. The reasons for this have to be investigated further.

The technology and applications of optical fibers have progressed very rapidly in recent years. Fiber-optic sensors have been commercially successful and well established in various industries from biomedical to defense. They exhibit many advantages over their electrical counterparts, including higher responsivity, higher detection bandwidth, higher temperature performance, better immunity to electromagnetic interference, all-dielectric composition, greater environmental ruggedness and distributed sensing capability. However, the physical dimensions and the minimum bend radius of the optical fiber sets a lower limit on the final package size. In applications where the working space is stringent or where physical intrusion must be minimized, it becomes highly desirable to develop ultra-compact sensors that can maintain the level of performance despite the miniaturization. The recent emergence of optical microfibers has opened up a new era of technological innovations. Microfibers have the potential to solve the problem with its range of enabling properties, including large evanescent field, strong optical confinement, bend insensitivity, low stiffness and high configurability. This thesis focuses on the innovative development of relatively unexplored areas of microfiber-based sensing as well as the envisioning of performance-enhancing techniques that can shape the on-going development of such sensors. In particular, extensive advancement was made in light of the simple demonstration of a novel current sensor with potentially gigahertz detection bandwidth. This includes the development of the resonator design to achieve higher compactness, and the first reported fabrication of the spun optical microfiber to counter the effects of linear birefringence. Well established and successfully proven sensing configurations such as the flexural disc and air-backed mandrel were adopted to create miniaturized microfiber-based accelerometers and microphones, with potential responsivity enhancements of at least one order of magnitude.

Design and first characterisations of the mobile sensor head in the Gravity Gradient Technologies and Opportunities Programme (GGtop) are presented. The aim of the project is the development of a mobile gravity gradiometer and faces the challenge of condensing a normally lab filling experiment in a portable and robust package. A fibre network replaced free space optics light distribution and fibre based components free space equivalents. Although stable against misalignment, the systems performance is limited by polarization changes of the guided light which arise from birefringence fluctuations along the length of the network due to external temperature fluctuations and mechanical disturbances. These instabilities limit the achievable temperature of the trapped rubidium 87 cloud to approx. 18μK. In preparation for gravity measurements, Rabi oscillations and Ramsey fringes with a λ/2 time of 7.4μs were successfully demonstrated in a co-propagating Raman beam configuration. The atom cloud was launched as a first step towards gravity gradiometry. As the system was designed to be portable, the complete system fits into a 1.5m x 2m x 0.5m package, plus a 14u rack of support electronics.

La microbalanza de cristal de cuarzo (QCM) se usa como técnica alternativa de análisis químico, donde las aplicaciones dependen directamente de la sensibilidad del cristal. Por tanto, es el parámetro más importante que determina el uso de los cristales de cuarzo frente a otras técnicas. La ecuación de Sauerbrey, teóricamente relaciona la variación de la densidad de masa en la superficie del cristal con el cambio de la frecuencia y al mismo tiempo predice que la sensibilidad aumenta en la misma proporción que el cuadrado de la frecuencia fundamental de resonancia serie del cristal. Aumentar la frecuencia fundamental de trabajo para aumentar la sensibilidad, es una necesidad; el objetivo principal de esta tesis doctoral es estudiar los sistemas de caracterización de resonadores de cuarzo, que se usan en la actualidad y proponer un sistema o una mejora a los ya existentes que permitan el uso de cristales de cuarzo de alta frecuencia de fundamental (HFF-QCM). De los sistemas que en la actualidad caracterizan a la microbalanza de cuarzo, se destacan los analizadores de impedancia y los osciladores, como métodos de caracterización de HFF-QCM. Los analizadores, por su gran tamaño y coste, quedan relegados a su uso como instrumento de referencia en el laboratorio. Los osciladores en cambio, por su bajo coste, su capacidad de integración, su sencillez del circuito y la monitorización continua de frecuencia de oscilación, lo hacen adecuados como interfaz para sistemas sensores basados en QCM. En esta tesis, se propone un sistema oscilador, basado en un oscilador diferencial equilibrado, como sistema de caracterización de cristales a 10 MHz, estudiándose el comportamiento del circuito, la capacidad de este sistema para compensar la capacitancia paralela del cristal, las aplicación de este tipo de interfaz para la caracterización de líquidos y finalmente se desarrollo una aplicación como inmunosensores piezoeléctricos para la detección del pesticida Carbaryl.
Montagut Ferizzola, YJ. (2011). Sistema Oscilador Mejorado para Aplicaciones de Microbalanza (QCM) en Medios Líquidos y Propuesta de un Nuevo Método de Caracterización para Biosensores Piezoeléctricos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/9688
Palancia

QCM sensor is a response to a kind of broad spectrum, high sensitivity, and simple structure, low-cost detection device, and particularly its quality as a type of gas sensor is widely used. With the successful oscillation in liquid phase, QCM sensor has been involved in the application analytical chemistry, surface chemistry, biochemistry and environmental monitoring side and many other scientific fields. With sensitive surface film as the sensitive element, AT-cut quartz crystal as energy transducer components by changes of the relationship between mass of surface film and frequency of QCM sensor transduces signals of mass or concentration into output frequency signal of sensor, thus achieve changes of mass or concentration detection. This paper mainly states how to design a low-cost QCM system platform with Arduino microcontroller board based on QCM sensor specific properties. For the oscillator circuit selection and differential frequency circuit design, the shield board has properly matched Arduino Mega2560, then by programming code to make Arduino acquire frequency of QCM sensor in real-time. Meanwhile, the interface and data store are corresponding convenient for real- time observing and data post-processing. By the tests of anhydrous ethanol evaporation, QCM system platform was calibrated and Sauerbrey equation verification. Moreover, this paper studies that photocatalytic degradation processing of Rhodamine B (RB) and methyl orange solution at the Surface of nanocrystalline TiO2 by QCM sensor.

This thesis presents for the first time two complementary techniques to monitor the optical path length in optical fibre over both long and short sensing lengths. Both techniques may be used to measure the physical environment of the optical fibre, in particular strain and temperature, and are suitable for multiplexed operation. Signal-to-noise analysis shows that current optical time domain reflectometry (OTDR) systems do not fully exploit the spatial resolution theoretically available. A new OTDR technique exploits the theoretical findings to monitor the range of reflective markers in an optical fibre. Measuring strain in fibre sections of several metres is demonstrated. 100?m spatial resolution has been achieved with a pulse duration equivalent to 1 m fibre length and within one second measurement time. The first fibre Bragg grating interrogation system using an acousto-optic tunable filter (AOTF) is described. The interrogation system locks the AOTF wavelength to the wavelength of a selected grating. Measuring the frequency of the AOTF control signal provides an accurate measurement of the grating wavelength. A detailed system analysis is presented to enable the optimisation of system parameters. A wavelength resolution corresponding to 0.4 microstrain is achieved within 0.1sec measurement time, close to the resolution predicted by the system model. This technique allows the use of fibre gratings as sensors for the measurement of both quasi-static and dynamic strains. The combination of the two systems facilitate the utilisation of optical fibre to monitor a structure both over a few metres and at critical points. Both sensor types offer new measurement possibilities as embedded structure monitors, for example for in-service health and usage monitoring or as nerves for active control of smart structures.

This thesis presents three novel optical fibre sensor systems which monitor optical path lengths. The systems have been used to measure strain in an optical fibre. All three systems make several measurements at different locations along a fibre, allowing the spatial distribution of a measurand to be obtained. For the first time, incoherent optical frequency domain reflectometry is used together with time division multiplexing to measure the optical path length of an array of fibre sections. Sensing sections are 5m long and are defined by broadband optical reflectors. A closed loop interrogation system is demonstrated to monitor the sensors in real time with an accuracy of 2.1µ(epsilon)/(root)Hz, in good agreement with the theoretically predicted value. Simultaneous monitoring of multiple fibre Bragg grating sensors, several millimetres in length, is also demonstrated by simultaneously generating multiple passbands in a single acousto-optic tunable filter. This is the only technique demonstrated to simultaneously monitor multiple gratings using a single wavelength-tunable device. The first distributed Bragg grating sensor to measure arbitrary strain profiles is also demonstrated. Low-coherence interferometry selects the interrogation position and a tunable filter measures the local wavelength. Two configurations of the technique are presented, which have achieved spatial resolutions of 300µm and real-time strain measurements with 5.4µ(epsilon)/(root)Hz accuracy, showing good agreement with theoretically predicted values. The only grating sensor network to be both distributed and multiplexed is presented together with the first results.

Thickness shear mode (TSM) sensors, also known as quartz crystal micro-balances (QCM) are a class of acoustic wave sensors that have been used for gas/vapor sensing. Fast and sensitive chemical vapor sensing, specifically of hydrocarbon vapors is an important application for these vapor sensors. The TSM sensors typically used have a lower sensitivity compared with other acoustic wave sensors. This thesis describes the development of high sensitivity organic vapor sensors using thin polymer film coatings on TSM devices. Commercially available AT-quartz TSM devices were milled leaving a thin quartz membrane surrounded by a thicker outer ring. This resulted in an increased frequency and a consequent increase in sensitivity, as described by the Sauerbrey equation. The TSM sensors were then coated with thin sensing films of rubbery polymers. Isothermal experiments at room temperature were conducted. A fully instrumented and automated test bed consisting of a temperature-controlled organic vapor dilution system, a precision impedance analyzer, and computer based data acquisition was developed and used to evaluate the performance of the coated TSM devices. The TSM devices compared in this study were AT cut with fundamental resonant frequencies of 10, 20, and 96 MHz. The results of tests conducted are presented to demonstrate increase in sensitivity for higher fundamental frequency TSM devices. 96 MHz TSM resonators were found to be 8 to 27 times more sensitive than 10 MHz resonators. Sensitivity was limited by the difficulty in coating sensing layers and damping of the resonator. Additionally, each sensor was evaluated and compared in terms of detection limit and noise level. 96 MHz resonators had higher noise levels than 10 MHz or 20 MHz resonators; as a result, 96 MHz resonators did not show significant improvements in LOD. Also, response times for 96 MHz resonators were quicker than 10 MHz or 20 MHz resonators and response times generally decreased with analyte concentration. Several rubbery polymer films as well as copolymers were investigated to determine which sensing film would have the optimal performance in terms of response time, recovery, reproducibility, repeatability, frequency noise, and baseline drift. The organic vapors studied were benzene, toluene, hexane, cyclohexane, heptane, dichloroethane, and chloroform at levels ranging from 0.2 to over 13.7 volume percentage in nitrogen gas. The Butterworth-VanDyke (BVD) equivalent circuit model was used to model both the perturbed and unperturbed TSM resonator. Monitoring the sensor response through the equivalent circuit model allowed for discriminating between the organic vapors. Vapor discrimination, in turn, depended upon the changes in the resistance parameter. Finally, the vapor liquid equilibrium at the polymer solvent interface was utilized to correct for perturbations, due to temperature changes, in the sensor response.

This thesis presents the development of two new types of polarimetric distributed feedback (DFB) fibre laser sensors for simultaneous strain and temperature measurements. These fibre Bragg grating (FBG) based sensors offer strain and temperature measurement accuracies of ±0.3 - ±15 με and ±0.04 - ±0.2°C which are suitable for many applications. The main advantage of these DFB fibre laser sensors over other FBG based sensors is the simplicity of their interrogation system. The first type of sensor operates stably in a single longitudinal mode which splits into two orthogonally polarised modes. This sensor utilises the wavelength of one polarisation mode and the RF beat frequency between the two polarisation modes. The system complexity is reduced to a minimum in the dual longitudinal mode polarirnetric DFB fibre laser sensor which utilises the RF beat frequencies between two longitudinal modes and their associated orthogonal polarisations, therefore requiring only a simple and cost effective frequency counter. -ions and pump excited state absorption into account. An extended version of this model incorporates, for the first time, self-heating in DFB fibre lasers which is caused by non-radiative decays. The performance of DFB fibre lasers employed in telecommunication applications is likely to benefit from these modelled results, which are also verified by experimental data.

This thesis reports on work performed within the field of optical fibre sensors. The topics studied cover three main areas of sensor research; fibre-remoted gas detection, the optical actuation of a resonant quartz device, and the assessment of compound glasses and fibres for current measurement applications. The gas detection techniques described have the common advantage of highly-selective measurement, and are applied to a number of industrial and environmental gases. Selectivity is achieved by effectively monitoring the spectral overlap between the gas sample to be measured, and that of a reference gas. Three techniques were employed to vary the spectral overlap, including Stark, pressure, and frequency modulation. For quantitative gas detection at atmospheric pressure, the modulation techniques are demonstrated here for the first time with fibre-remoted sampling cells. Practical examples of sensors for detection of methane, ammonia and carbon dioxide were demonstrated, and gas sensitivities down to 50ppm by volume were achieved. The optical powering and readout of a quartz resonator was demonstrated. An open-ended tuning fork device was used, and a novel interferometric technique was employed to minimise the optical drive power required. Threshold optical power levels of less than 25µW were achieved. The configuration was capable of operation with only a single fibre link to the sensor head, to carry both optical drive and readout signals, and a single optical source was employed. Optical fibre current monitors employing the Faraday effect can suffer measurement bandwidth restrictions if a long fibre is employed in order to attain good sensitivity. As the Faraday effect in many compound glasses is considerably stronger than for a standard silica fibre, then an equivalent sensitivity can be achieved for a shorter fibre coil by the use of compound glasses. The sensitivity and bandwidth of a typical current monitor configuration are analyzed for a number of compound glasses for the first time. The Verdet constant of a trial fibre fabricated from one promising compound glass was measured.

More than 6 billion people worldwide consume milk and milk products and this number is rapidly growing every year (FAO, 2015a), there are numerous occurrences where the milk quality was below acceptable standards causing severe health hazards among consumers including young children. The aim of this research work is to design and develop a novel, microwave spectroscopy, approach for determination of overall quality of milk. In particular, this quality determination of milk products was achieved by identification of deterioration or spoilage of milk over time, classification of the milk product based on composition (e.g. fat content), in addition to the contamination (e.g. adulteration due to presence of detergents, urea). An extensive literature review was carried out to establish the scope of the PhD work and in order to achieve the objectives. Current advancements were studied along with the traditional methods of milk quality testing to identify the key areas where further development can take place to enable the quality control of milk products outside the laboratory premises. This work addresses the drawbacks in currently employed methodologies and attempts to overcome or minimize their overall limiting effect. The application of this sensor system is aimed within the milk supply-chain hierarchy after the production at dairy plants and before sale to allow easy and real-time quality testing. The dielectric property tests were conducted to produce unique spectral signatures for three mainly consumed categories of fresh milk; whole milk, semi-skimmed milk and skimmed milk bought from a supermarket over a period of a week, which served to build a reference database. Based on these spectral signatures for the three categories of milk, a planar, microwave resonator sensor acting as a fluidic sensor was designed, simulated and fabricated to determine spoilage, classification of milk and identify presence of contamination. This work has achieved distinct results to verify the statement, followed by validation, to serve as a platform for the establishment of a laboratory based prototype model to test overall quality of milk products, with coefficient of determination R2 ≥ 0.95 in all experimental measurements.

In this work, the suitability of amorphous semiconductors as hard field optical sensors for application in optical process tomography (OPT) has been established. Two amorphous semiconductors were selected for the study, these being amorphous arsenic triselenide (a-As 2 Se3) and hydrogenated amorphous silicon (a-Si:H). The a-As2Se3 device was a single layered structure of 60|Um thickness fabricated upon a 2mm thick cylindrical aluminium substrate. The a-Si:H device was a multi-layered structure of 27.1fim overall thickness fabricated upon a 4mm thick cylindrical aluminium substrate. 20mm 2 samples were cut from the cylinders, their surface being left free for a xerographic investigation. For a tomographic investigation, semitransparent gold (Au) contacts were sputtered onto the surface of the devices to produce single contacts or contact arrays. The study comprised of the two fields of xerography and tomography. The xerographic study comprised of the measurement of such parameters as charge acceptance, dark decay, residual potential, and photoinduced discharge. The research project has concurred with other workers in that the dark discharge mechanism in a-As 2 Se 3 proceeds via a xerographic depletion discharge process, and a Poole-Frenkel type emission in a-Si:H. The tomographic investigation involved the study of such parameters as detectivity, responsivity, steady state photocurrent, and photoinduced fatigue. Detectivity has found to be dependant upon the magnitude of applied electric field and level of incident irradiance. Irradiance in the order of 3.45mW/cm 2 to 9.57mW/cm 2 for a- fj f\ As 2 Se3 and 5.31mW/cm to 28.32mW/cm for a-Si:H was required in order to produce a clean and repeatable photogenerated current pulse over the range of electric fields specified (0.66xl05 V/cm to 1.66xl05 V/cm). The production of steady state current has found to be dependant upon the magnitude of electric field, the level of irradiance, and the illumination period. Irradiance of 319mW/cm 2 to 1.46W/cm2 with an illumination period of 520ns was required to produce steady state photocurrent in a-As2Se3 , and 693mW/cm2 to 2.62W/cm 2 with an illumination period of 880ns for a-Si:H. A linear relationship between electric field and responsivity has been observed in both materials over a range of irradiance of 3.45mW/cm 2 to 9.57mW/cm2 . Responsivity in the order of 87.86|LiAAV to 145.19|iA/W for a-As2Se 3 and 14.19(iAAV to 103.81)J,AAV for a-Si:H has been demonstrated. An investigation as to the effects of photoinduced fatigue in both a-As 2 Se3 and a-Si:H has been carried out by the application of pulsed visible light of various flash repetition rate (FRR) under a constant high electric field over a 30 minute illumination period. It has been shown that the rate of fatigue is dependant upon the material, time, electric field, light intensity, and FRR. A maximum operating speed of 20Hz has been determined for a-As 2Se 3 and lOOHz for a-Si:H. The maximum operating speed of 20Hz for a-As 2 Se 3 was deemed unsuitable for OPT application and the a-As 2 Se 3 material was eliminated from further tomographic investigation. Tomographic prototypes were employed to establish the a-Si:H devices ability to produce qualitative and quantitative data. The results of this investigation demonstrated that 1mm changes in water level and 0.5% changes in fluid colour could be accurately determined by the a-Si:H device at speeds required for OPT. The use of an a-Si:H device containing a Au contact array facilitated the imaging of the curvature of a pipeline and a phantom object contained within the pipeline. The results of the overall investigation have confirmed that the a-Si:H device is suitable for application as a hard field optical sensor for OPT.

In this study a biosensor based on real time quartz crystal microbalance (QCM) monitoring is optimized and characterized for the application in the Norosensor. This biosensor is aimed to recognise, capture and amplify Norovirus (NoV). In an initial step a simplified bioassay was developed that focuses on the latter parts of the assay which consists of DNA-guided probing and amplification of the captured virus and includes the development of an amplification model assay directly to the functionalised crystal surface. A padlock probe with matching sequence to the conjugated oligonucleotide on the quartz crystal surface is used as target in the model assay. Although a number of studies have been carried out based on padlock probe ligation and rolling circle amplification (RCA) based QCM sensing, these studies utilize the entire crystal surface to capture and amplify the biomolecule. In this research work the QCM monitoring is explored on a centrally functionalised electrode surface through conjugation only at the centre of the electrode for increased mass sensitivity. Thus, allowing capture and amplification of the padlock probe only at the centre of the quartz crystal. A 14mm diameter, thermoncompensated AT-cut, nonpolished quartz crystal with a 10mm diameter gold surface coating acting as electrode was utilized for QCM measurements. The detection system is based on mass binding and amplification on the QCM to produce a negative frequency shift in the fundamental frequency of the vibrating quartz crystal. The amplification products were additionally fluorescently labelled and fluorescent microscopy images were also obtained at the end of every experiment to verify the presence or absence of DNA capture and amplification. Experimental findings show that the current flow chamber with a 15ul capacity is able to detect a specific padlock probe concentration of 1nM on a conjugated region of ~2.5mm diameter. RCA amplified the mass with an average frequency shift of -80Hz in 60mins RCA incubation time. Further, the specificity and sensitivity of the QCM system was explored. However, the system has limitations where sensor binding of reaction proteins, such as DNA ligase and BSA, to some extent is observed. The storage stability of the functionalized self-assembled monolayer (SAM) on the QCM is also observed to deteriorate and thus, is of concern. Nevertheless the combination of RCA based amplification with QCM real-time monitoring has the potential for rapid and simple, low cost detection of the Norovirus.
I det här arbetet har vi optimerat och karateriserat en biosensor för detektion av Norovirus som orsakar häftiga utbrott av kräksjuka under vinterhalvåret vilket leder till både försämrad vård samt stora ekonomiska förluster för samhället. Målet inom EU projektet “Norosensor” är att utveckla ett snabbtest som kan tillämpas efter ett utbrott på till exempel en vårdavdelning och som ska mäta mängden virus i luften vilket kan fungera som riktlinje för om en avdelning är säker att användas eller ej. Tekniskt är målet med testet att fånga in viruspartiklar från luften som specifikt binds till sensorytan. Därefter ökar vi känsligheten från bundna partiklar genom en DNA-baserad amplifiering. Detta genererar specifik, viruskorrelerad massa som mäts med en kvartskristall mikrovågs sensor. När massan ökar minskar frekvenser vid vilken kristallen vibrerar och detta mäts i realtid. Det här arbetet har inte behandlat infångande eller inbindning av virus utan har fokuserat på den senare delen av protokollet som omfattar amplifieringen på sensorytan. En modell-assay har därför utvecklats där viruspartikeln istället representeras av en så kallad “padlock probe” (hänglås probe). Då sensorn är mycket känslig har först olika protokoll testats för effektiv rengöring av ytan med hjälp av ultraljud. I nästa steg har ytan funktionaliserats med thiol-modifierade syntetiska DNA molekyler som används för infångningen av målmolekylen på sensorytan (virus eller i detta fall padlock proben). Det har tidigare uppskattats att för att få maximal känslighet i massmätningen så är det fördelaktigt att binda viruset endast i mitten på en mycket liten yta av kristallen. Den här avhandlingen har därför fokuserat på att utveckla protokoll för detta där ytan först funtionaliserats i mitten innan resten av ytan blockats för att undvika ospecific inbindning. Resultaten visar att vi kan generera en centrerad funtionalisering och att vi får låg ospecifik binding. Protokollet består av flera biokemiska reakionssteg såsom (i) inbindning och lingering av padlock probe och (ii) amplifiering av den ligerade proben genom “rolling circle amplification”. För att kunna verifiera att vi fått amplifieringsprodukter på ytan har vi dels mätt frekvensändringen på grund av ökad massa men också märkt in dem med fluorescerande molekyler och detekterat dem i microskop. Under arbetets gång har ett flertal olika typer av kristaller testats. Det visade sig att om en polerad yta används (1μm grovhet) så migrerade molekylerna iväg från mitten när vi oscillerade kristallen medan vi fick bättre resultat om något grövre (3μm) ytor användes. Vi testade även ett flertal olika flödesceller av olika material och med olika reaktionsvolymer. Eftersom kristallen är mycket känslig så påverkar faktorer som flödeshastigheter och eventuella luftbubblor frekvensen. Vi optimerade därför detta och körde mätningarna vi6konstant flöde men med alternerande, låga hastigheter när vi tillsatte nya reagens eller inkuberade reaktionerna. Vi förvärmde även reaktionsmixarna för att minska ospeficika effekter och konstaterade att den funktionaliserade ytan påverkades av lagring över tid. I våra försök såg vi att protein såsom ligeringsenzymet och albumin, vilka har förhållandevis stor massa, hade effekter på frekvensen redan i sig genom att binda till ytan. Ytterligare optimeringar måste därför göras framöver för att minska denna inbinding bland annat genom bättre tvättsteg. Vi kunde dock påvisa linjär massökning med ökad amplifieringstid och har bevisad hög specificitet. Slutligen utvecklades ett litet mjukvaruprogram för att automatisera analysen och minska bruset. Sammanfattingsvis har vi lyckats utveckla ett enkelt och snabbt system för specifik massamplifering av Norovirus.

This thesis reports work carried out to develop an optical sensor capable of detecting disturbance of optical fibre cables, for application in protection of telecommunications infrastructure. Initially, three types of sensor were investigated, however after preliminary experimental and theoretical work it was decided to concentrate on a novel coherent-optical time-domain reflectometer (C-OTDR). The operation of the C-OTDR has been investigated theoretically, using various models to describe coherent scattering in the optical fibre. The assumptions used in the models were applied to a numerical simulation of coherent scattering, obtaining results in good agreement with theoretical predictions and experimental measurements. Having developed a clear explanation of the sensor's operation, a detailed noise analysis is carried out, enabling the limiting factors to be identified and minimised. The design and development of a portable sensor system is then described, and the results from a number of field trials are presented. Seeking to explain unexpected observations during these trials, a detailed experimental and theoretical analysis of the limits due to optical non-linearity was carried out, showing that the pulse power is limited by the need to prevent spectral broadening due to self-phase modulation, which adds noise to the sensor output. Applying the findings of these investigations, further field trials and laboratory tests were carried out with improved experimental C-OTDR sensors. By optimising the pulse power and carefully controlling the noise sources, it has been possible to demonstrate operation at longer ranges, with superior spatial resolution, than has been reported for other sensors of this type.

Focus of this thesis are the magnetic shielding aspects of a mobile atom interferometer, developed under the Gravity Gradient Technologies and Opportunities Programme (GGtop). This system has been used as a test bed for new compact technologies with the aim to perform outdoor gravity gradient measurements. A finite element analysis model was used for optimising magnetic shielding design, aiming to reach a field attenuation factor of the order of 103, by mu-metal. The research was extended to alternative shielding techniques with the intention to push current technology towards next generation portable atomic sensors. Initially, Metglas foil was used to create lightweight cylindrical shielding housings. The performance goal was approached by a total of 37 foil wrappings around two coaxial cylinders. However, material inhomogeneities affected the magnetic field uniformity. The second approach exploits additive manufacturing of permalloy-80 for 3D-printing compact shielding structures. Process optimisation was undertaken by fabricating approximately 70 small bulk samples under different printing parameters, while 6 cylindrical shield prototypes were produced for preliminary shielding tests. Application of post heat treatments enhanced shielding effectiveness by a factor of up to ~ 15, indicating that a performance closer to mu-metal could potentially be reached by further process optimisation.

The report deals with the study of the resistence of the nonporous polymer materiále against permeation of the selected TICs, with the analysis of the running difussion processes and utilization of the acquired results for the selection of suitable barrier materials for the protective means.

This thesis describes the design, fabrication and characterisation of diffraction-based sensors on silicon (100) substrates for the detection of complementary DNA sequences using colloidal gold labels. In-depth analysis of variations of DNA sequence within the human genome and association with diseases is expected to lead to personalised medical treatment. There is a great need for DNA analysis technologies and for techniques to determine whether sequence variations occur on the same chromosomal strand with applications in disease screening and diagnosis. Novel two-dimensional diffraction structures are designed and fabricated. It is shown that two-dimensional diffraction approaches may potentially offer multiplexing of DNA detection assays.

Research on fluorescence-based integrated optical immunoassay multisensing systems has gained growing interest in the last ten years. This is because the systems have the potential to simultaneously detect multiple analytes in a single measurement, and the techniques involved are fast, robust and cost-effective. Therefore they have the potential to replace conventional chromatographic techniques, as the monitoring systems for the rapid assessment of water or food samples. Other areas, such as clinical diagnostics or forensic science also have a demand for highly multiplexed analytical systems. This thesis presents a novel 32-analyte integrated optical fluorescence-based multisensor, and its integration to an automated multi-bio-sensing system. This system is primarily used for detecting organic pollutants in river water. A detailed study was also carried out with a CCD detector system, used to replace the fibre collection and photodiode array system and allow straight forward extension to more than 32 analytes. A direct comparison between these two systems is also presented

This research is conducted as a part of EU FP7 project entitled NEMSIC (hybrid nanoelectro-mechanical/integrated circuit systems for sensing and power management applications) with project partners, EPFL, TU Delft, IMEC-NL, CEA-LETI, SCIPROM, IMEC-BE, Honeywell Romania, and HiQSCREEN. Nano-electro-mechanical (NEM) sensors are getting an increased interest because of their compatibility with “In-IC” integration, low power consumption and high sensitivity to applied force, external damping or additional mass. Today, commercial biosensors are developed based on mass-detection and electro-mechanical principles. One of the recent commercial mass-detection biosensors is a quartz crystal microbalance (QCM) biosensor which achieves the mass sensitivity of a few tens pico g/Hz. The newly developed in-plane resonant NEM (IP R-NEM) sensor in this thesis achieves the mass sensitivity less than zepto g/Hz that is over nine orders smaller than that of the commercial QCM sensor using a much smaller sensing area compared to the QCM sensor. This fact will make the IP-RNEM sensor a world-unique sensor that shows a very high sensitivity to a very small change in mass. The stated mass sensitivity is achieved by modelling the functionalization and detection processes of the suspended beam. For modelling the linker molecules in the functionalization process, a conformal coating layer in different configurations are added to the suspended beam and the sparse distribution of target molecules in the detection process is modeled by changing the density of the coating layer. I would like to clarify that the scaling rule of the mass responsivity is given by k4 regardless of the different functionalization configurations. I develop a completely new hybrid NEM-MOS simulation technology which combines three-dimensional finite element method (3D FEM) based NEM device-level simulation and circuit-level simulation for NEM-MOS hybrid circuits. The FEM device-level simulation module also includes new modelling of selfassembled monolayer for surface functionalization as well as adsorb ed molecules to be detected and facilitates quantitative evaluation of mass responsivity of designed NEM sensor devices. The basic part of the sensor, the NEM structure, includes a suspended beam and two side electrodes and that is fabricated at the Southampton Nanofabrication Centre (SNC). The fabrication at SNC includes a new sensor that uses a free-free beam that improves the quality factor up to five orders of magnitude at room temperature and atmosphere based on the numerical results. The IP R-NEM sensor consists of a suspended beam that is integrated with an in-plane MOSFET and is fabricated by CEA-LETI. The monolithically integrated NEM with the MOSFET on the same SOI layer for the sensor is a real breakthrough which makes it a potential low-cost candidate among the mass-detection based sensors. With respect to the conducted radio-frequency (RF) characterization for nano-wire devices in collaboration with the Tokyo Institute of Technology and NEM structures, the designing of an RF contact pad to reduce the effect of parasitic frequencies and doing the measurement at high vacuum to reduce the motional resistance and increase the quality factor are necessary for the characterization of devices with nano-scale dimensions. The integrated MOSFET in the IP RNEM sensor amplifies the output transmission signal from the resonating beam by its intrinsic gain. The fabricated sensors show a three orders of magnitude larger gain than that of the previously proposed resonant suspended gate FETs by biasing the MOSFET at the optimized voltage biases that are found based on the DC characterization of MOSFETs.

Fast-ion conducting glasses of the compositions Na1+xM2-x/3SixP3-xOI2-2x3 (0≤ x ≤3), where M = Zr, Ti, were studied to determine their structural arrangement, physical properties and ionic conductivity. Glass samples were prepared using the conventional melt-quench method in the melting temperature range, 1550 °C to 1650 °C. Glass products were characterised by XRD, DTA, dilatometry and density measurement. Solid state MAS NMR experiments of three accessible nuclei, 23Na, 29Si and 31P were used to determine short-range order arrangement in the glasses. XRD confirms the amorphicity of glasses for the compositions of x in range 0-3. Glass transition temperatures, Tg. TEC, and molar volume are controlled by glass composition. The MAS NMR results suggest that glass structure could be visualised as the silicate network modified by Na+ and Zr4+ or Ti4+ and [PO4] tetrahedra link up with the remaining of these modifiers with no Si-O-P observed. The glass structures were also controlled by the compositions. Using parameters determined by DTA, the corresponding glass-ceramics were produced by heat treatment for 4 hr. The composition containing ZrO2 provided the fast-ion conducting crystalline phase at a small concentration. The major crystalline phase is Na2ZrSi2O7. Glass-ceramics containing TiO2 produce very small concentration of the crystallised phase. Ionic conductivity measurement was used to determine the electrical properties of glass and glass-ceramics. Glasses having high Na2O content showed the higher ionic conductivity compared to the others.

In this work we present an analysis of gas sensors based on correlation spectroscopy with a Fabry-Perot interferometer (FPI). In this technique the spectral FPI transmission fringe pattern is matched with ro-vibrational absorption lines. To produce the cross correlation principle the FPI fringe pattern must be shifted along the frequency axis. Hence as the spectral FPI fringes are equidistant and symmetric therefore the ro-vibrational absorption lines of the target molecule must be almost equidistant. Well resolved ro-vibrational lines with Lorentzian line shapes and with almost equidistant spectral separation are characteristics of most diatomic and linear molecules, i.e. CO2, CO, N2O, and some specific absorptions bands of symmetric top and spherical top molecules eg. NH3, CH4 at one atmosphere pressure. In this work we review two general sensor designs, in the first the FPI it is illuminated with a collimated beam and in the second design the FPI it is illuminated by a converging beam. In the collimated beam design all the rays reaching the FPI have the same angle of incidence whilst in converging beam the incident rays have different angles of incidence. Hence the spectral FPI fringe pattern it is affected by the different angles of incidence and therefore it is essential to consider these effects during the evaluation of the sensor response. A novel analytical method based on the Fourier transform which gives a good insight of the gas sensor design based on correlation spectroscopy with a FPI it is presented which we call the convolution method. The method provides a simple way to evaluate much faster the sensor response, and using the Fourier transform characteristics the functions involved in the mathematical model of the sensor response the optimal cavity length of the FPI can be directly determined and it is shown that if the sensor signal will be recovered by a Phase Sensitivity Detector the optimum mirror reflectivity is 0.41 regardless of the other parameters. Moreover using the convolution method the optimal FPI mirror reflectivity can be quickly evaluated. The method also gives us guidance on selecting the best bandpass filter for the application. In this work we also review the effects of the blackbody converging beam and some possible solutions to minimize the effect of the degraded FPI fringe pattern are proposed. In this case it is important to consider the spurious FPI fringe patterns produced by reflection within the mirrors substrates of FPI mirrors. Finally based on all these knowledge we describe a full methodology to simulate the sensor response. It is important to mention that in our methodology we not use 'fitting parameters’ to adjust the simulated results with experimental measurements. Our experimental measurements strongly support the simulated sensor response obtained with our methodology. Therefore the methodology can be applied to design other gas sensors based on cross correlation spectroscopy with a FPI as a modulator. Moreover it is shown that these sensors present an almost negligible sensitivity to molecules other than the target. Finally based on our simulated and experimental results we can conclude that this sensor design configuration is viable to fabricate commercial gas sensors if the FPI and the detector are integrated within a MEMS structure.

This thesis reports on the progress that has been made improving the sensing performance of a distributed temperature and strain optical fibre sensor based on the coherent detection of spontaneous Brillouin scattering. To further improve the sensing range and the sensor's performance, the use of Raman amplification was investigated utilising different Raman pump configurations. Using frequency measurements only, a temperature resolution of 5 °C over a 150km sensing range with 50m spatial resolution was achieved using a counter-propagating Raman pump. Using co-propagating Raman pump the temperature resolution was 1.7 °C with 20m spatial resolution at 100km. Measuring both the power and frequency of the Brillouin signal, a simultaneous temperature and strain measurement was performed over 50km; temperature and strain resolutions of 3.5 °C and 85με with 5m spatial resolution were achieved, respectively, using co-propagating Raman pump which has the advantage of requiring access to just one end of the sensing fibre.

La miniaturisation des composants microélectroniques est nécessaire pour des gains de coûts, de place ou de performance. Des capteurs de gaz, faciles d'utilisation (transportables et non encombrants) peuvent alors être envisagés et ouvrir la possibilité à la détection de certains gaz toxiques en très faible quantité (tels que les COV, composés organiques volatils) qui ne sont que trop peu détectés actuellement. Les performances d'un capteur de gaz sont en premier lieu liées à sa couche mince sensible qui permet la détection par interaction avec le gaz cible. Ces travaux se focalisent sur le développement de couches sensibles de polymères réalisées par une technique de synthèse novatrice de dépôt chimique en phase vapeur par une polymérisation amorcée in-situ (iCVD). Cette technique possède de nombreux avantages pour la réalisation de composants nanométriques comme par exemple l'absence de solvant dans son procédé ou les faibles températures mises en jeu. L'impact des paramètres du procédé iCVD sur les propriétés du film mince est dans un premier temps discuté, et le mécanisme de croissance du film mince de polymère est par la suite étudié. Pour la première fois, deux régimes de croissance sont décrits. Le premier régime, ainsi visible pour de faibles temps de dépôt, est caractérisé par une vitesse de croissance faible. Le second régime apparaît à des temps de dépôt plus important et se traduit par une vitesse de croissance plus élevée et constante dans le temps. Grâce à de nombreuses caractérisations macroscopiques et microscopiques des couches minces de poly(méthacrylate de néopentyle), un modèle pour le mécanisme de croissance de film mince de polymère est proposé. Ce régime en deux temps semble être corrélé à l'épaisseur du film mince et une épaisseur critique est identifiée. De plus, pour comprendre cette croissance, un facteur primordial est mis en évidence. En effet, la concentration en monomère sur le lieu de la polymérisation est déterminante pour la croissance et permet la réalisation des films minces maîtrisés et reproductibles, nécessaires dans le domaine des capteurs de gaz. Différents polyméthacrylates déposés en couche mince par iCVD sont testés comme couche sensible. Ces films ont permis la détection du toluène en très faible quantité (ppm) et ont l'avantage de conduire à des capteurs réversibles
Miniaturization of microelectronic devices is mandatory for cost, space and performance benefits. Easy-to-use gas sensors can then be designed and detection of low level of toxic gases can be achieved. The sensor performances are closely dependent on the sensitivity of the thin film towards the targeted gas. This study focuses on sensitive polymer thin films deposited by initiated Chemical Vapor Deposition (iCVD). This innovative deposition method has the advantage to be solvent-free and does not require high reaction temperatures, which allows its use in many fields, including nanocomponent fabrication. The iCVD process parameters are investigated and their influence on the thin film properties discussed. The study of the growth mechanism reveals an unexpected two-regime growth of the deposited films. The first regime, in the early stage of the deposition process, is characterized by a relatively slow growth. In the second regime, the growth rate slightly increases and the film thickness increases linearly with the deposition time. Based on microscopic and macroscopic data gained on poly(neopentyl methacrylate) thin films, a model for the growth mechanism of the polymer thin film is proposed. The change of regime appears to be correlated to the thin film thick-ness. This study shows the presence of a critical thickness. Moreover, the monomer concentration building up where the polymerization takes place is the most significant parameter to understand the film growth. It is also the key parameter to enable the deposition of reproducible and thickness controlled films, which is required for gas sensor applications. Finally, polymethacrylate films, obtained by iCVD, are tested as sensitive layers and low toluene gas concentration (ppm) can be detected, while the gas sensors are reversible

O objetivo desse estudo foi determinar a vida útil da tilápia do Nilo (Oreochromis niloticus) inteira armazenada em gelo, usando analises sensoriais (Método do Índice de Qualidade), físico-químicas (bases nitrogenadas voláteis totais - BNVT, sustâncias reativas ao ácido tiobarbitúrico - TBARS, pH, cor, textura e microbiológicas (microrganismos mesófilos e psicrotróficos). Uma equipe de sete provadores foi treinada durante sete sessões para avaliação sensorial de frescor em peixe cru e filés cozidos. Um esquema QIM foi otimizado para tilápia inteira e outro desenvolvido para filés cozidos, com 19 e 12 pontos de demérito, respetivamente. Três lotes de tilápia foram usados e os exemplares foram armazenados durante 13 dias em gelo para avaliar as alterações dos atributos de qualidade (aparência, brânquias, olhos, parede abdominal). A vida útil da tilápia do Nilo armazenada em gelo foi determinada em oito dias com base no critério sensorial dos filés cozidos, e pode ser usada como referencia para predizer o tempo de conservação residual. O índice de qualidade apresentou uma alta correlação linear com o tempo em gelo (IQ = 1,3865 x dias + 0,7922, R2 = 0,96), assim como também todos os atributos de qualidade. As análises sensoriais mostraram ser adequadas e confiáveis para avaliar o grau de frescor da tilápia, porem é recomendado usar no mínimo quatro peixes e mais do que um avaliador. A firmeza diminuiu durante o tempo de conservação em gelo (r = -0,73). Há uma pobre correlação entre os índices físico-químicos e microbiológicos e o tempo em gelo, não sendo considerados parâmetros confiáveis para avaliação das alterações da qualidade da tilápia do Nilo. Porém, peixes com até 13 dias não representam um risco para o consumidor, considerando que não foram ultrapassados os teores limites de BVNT (< 30 mg N/100g) nem de micro-organismos mesófilos viáveis (< 107 UFC/g).
The aim of this study was to determine the shelf-life of whole Nile tilapia (Oreochromis niloticus) stored in ice, using sensory analysis (Quality Index Method), physicochemical (total volatile base nitrogen - TVB-N, thiobarbituric acid-reactive substances - TBARS, pH, color, texture and microbiological (mesophilic and psychrotrophic). A sensory panel of seven assessors was trained during seven sessions for sensory evaluation of fresh fish and cooked fillets. A QIM scheme was optimized for whole tilapia and other developed for cooked fillets, with 19 and by 12 points of demerit, respectively. Three batches of tilapia were used and the fish were stored on ice during 13 days to evaluate the changes in quality attributes (appearance, gills, eyes, abdomen). The shelf-life of Nile tilapia stored on ice was determined in eight days based on sensory analysis of cooked fillets, and can be used as reference to predict the remaining shelf life. The quality index had a high linear correlation with time on ice (QI = 1.3865 x + 0.7922 days, R2 = 0.96), as well as all quality attributes. Sensory analysis showed to be adequate and reliable for assessing the degree of freshness of tilapia, however it is recommended to use at least 4 fish and more than one assessor. The firmness decreased during the ice shelf life (r = -0.73). There is a poor correlation between the physical, chemical and microbiological indexes and the time stored on ice, whereby they\'re not considered reliable parameters for assessing changes in quality of Nile tilapia. However, fish up to 13 days do not represent a risk for the consumer, considering they were not exceeded the limits of TVB-N levels (< 30 mg N/100 g) and also not the viable mesophilic microorganisms (< 107 CFU / g).

This thesis describes experimental and theoretical studies of interrogation systems for determining fluorescent decays of order a few microseconds. The studies have enabled optimised design of interrogators for sensing oxygen using a fluorescent polymerencapsulated ruthenium complex. Two basic interrogation methods were explored, using blue LED excitation. The Rapid Lifetime Detection (RLD) scheme, a fluorescence interrogation method based on direct interrogation of the decay curve following pulsed excitation was generalised, and a novel method for optimising measurement precision derived. The effect of background light on the optimum was quantified. Dissolved (aqueous) oxygen concentration was measured to a precision of 1 part per billion using a 1 second response time (the peak fluorescence power was only 12.5±0.5pW). A second interrogation method, where the phase delay between an intensity modulated excitation source and the resultant fluorescence is processed to make measurements, was for the first time, fully analysed for measurement of exponential decays. When measuring fluorescence lifetimes in the range 2.9-3.3μs, a precision of 2.3 x 10-10 s Hz-0.5 was achieved. (The peak fluorescence power was 500±25pW). A novel combination of ruby optical temperature sensor insert and oxygen sensing layer was demonstrated as a simultaneous temperature and oxygen sensor. A new fluorescence calibration standard consisting of thermally stabilised titanium-dopedsapphire sample was constructed to calibrate and test the indicators. This work was sponsored by a BRITE EuRam European project, which helped determine the priorities of the research.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The combined use of the Sequential QM/MM method with the ASEC mean field approximation [1] and the Free Energy Gradient method [2] has been very successful in describing the electronic structure of molecules in solution [3]. The advantage of this combination is that it permits the usage of an atomic- level modeling of the whole system, in contrast to continuum models, and, at the same time, it is less computationally expensive than ab initio or QM/MM simulations, even allowing the employment of more sophisticated electronic structure methods. In this context, the present work deals with the study of conformational and electronic structure, in solvent medium, of two organic compounds, DMACA and Phenol Blue, which have in common the characteristic of having acceptor-donor groups. The study is conducted in the presence of nonpolar, polar protic and polar aprotic solvents. It is adopted as basic methodology the ASEC-FEG, but also it is made a study with a continuum method, namely PCM. The results show that the solvent effect causes a significant geometric distortion of the molecules of interest while causing an internal charge displacement from donor group to acceptor group. Both effects are more pronounced in protic and aprotic solvents but mainly in protic solvents, in which hydrogen bonds lead to a greater solute polarization. The absorption spectra of these molecules, calculated by TD-DFT (CAM-B3LYP), directly reflect these changes. For all solvents, the absolute values of electronic transitions and their respective solvatochromic shifts are in good agreement with the experimental results.
O uso combinado de métodos QM/MM sequencial com uma aproximação de campo médio (ASEC) [1] e o método do Gradiente de Energia Livre [2] tem tido sucesso na descrição da estrutura eletrônica de moléculas em solução [3]. Uma das vantagens dessa combinação é que ela permite o tratamento do sistema soluto-solvente em um nível atomístico, em contraste com modelos contínuos, e tem a vantagem de, ao mesmo tempo, ser uma metodologia menos cara computacionalmente do que simulações QM/MM ab initio [4]. Nesse contexto, o presente trabalho versa sobre o estudo da estrutura conformacional e eletrônica, em meio, de dois compostos orgânicos, DMACA e Phenol Blue, que tem em comum a característica de possuir grupos aceitador e doador de elétrons. O estudo é realizado na presença de solventes apolares, polares apróticos e polares próticos. Adota-se como metodologia básica o método QM/MM sequencial utilizando o ASEC, mas faz-se também um estudo com um método contínuo conhecido, o PCM. Os resultados mostram que o efeito de solvente provoca uma signifativa reestruturação geométrica das moléculas de interesse, ao mesmo tempo em que causa um deslocamento interno de carga do grupo doador para o grupo aceitador. Os dois efeitos são mais pronuciados em solventes apróticos e próticos, mas principalmente nos solventes próticos, em que as ligações de hidrogênio levam a uma maior polarização do soluto. Essas mudanças refletem diretamente no espectro de absorção, calculado por TD-DFT (CAM-B3LYP), dessas moléculas. Dos meios apolares, passando pelos polares apróticos, indo até os polares próticos, os valores absolutos das transições eletrônicas e seus respectivos deslocamentos solvatocrômicos encontram-se em bom acordo com os resultados experimentais.

Over the past two decades, distributed optical fibre sensors (DOFS) based on Brillouin and Raman scattering have been extensively studied. As a result, a wide range of distributed temperature and strain sensors with different sensing range and accuracy levels have been developed. However, due to the weak nature of Brillouin and Raman scattering, most of the research in this field has been focused on DC or quasi-DC measurement of temperature and strain. On the other hand, the Rayleigh-based DOFS which have been previously proposed are only able to detect dynamic disturbances along the sensing fibre. In this thesis, a new sensing technique has been developed which is capable of quantifying and tracking multiple dynamic perturbations along the sensing fibre, simultaneously. The sensing mechanism of the proposed technique relies on the phase of the Rayleigh backscattered light. For any given segment along the fibre, the difference in the phase of the backscattered light radiating from the two ends of that segment changes as a function of the external perturbations at that segment. Therefore, dynamic vibration along the sensing fibre can be extracted by comparing the phase of the backscattered light from two different sections of the sensing fibre. By implementing this technique using an imbalanced Mach-Zehnder Interferometer (IMZI), a distributed sensor was developed that was capable of quantifying dynamic perturbations within the frequency range of 200Hz ~5kHz along a 1km sensing fibre. Furthermore, the same principle was used to develop a distributed magnetic field sensor. By coupling an optical fibre to a magnetostrictive wire and by using this combination as a magnetic field to strain transducer, a distributed magnetic field sensor was formed with magnetic intensity range of 1Gs~ 8Gs and frequency range of 50Hz ~5kHz. In addition, the IMZI arrangement was used as a frequency-to-intensity convertor to develop a distributed dynamic strain sensor based on Brillouin scattering. The proposed sensor exhibited a strain range of 400µέ 4mέ and a sensing range of 2km.

Optical fibre sensors have offered such unrivalled distributed sensing features that they continue to be successfully exploited in various industries for performing continuous measurements of the physical parameters, such as, temperature and strain. However, there arise certain conditions in engineering or materials manufacturing and characterisation environments, when the user seeks to extract the knowledge about a single physical parameter only, say strain, whilst the environment is also subject to temperature. This thesis explores techniques to offer solutions under such conditions by developing a high spatial resolution temperature compensated distributed strain sensor. The preliminary exploration involved exploiting the high spatial resolution Brillouin frequency based Brillouin optical correlation domain analysis technique in combination with the anti Stokes Raman intensity based optical time domain reflectometry technique. This work resulted in achieving a temperature compensated strain resolution of 46με with a spatial resolution of 24cms over a sensing length of 135m. Tackling the impact of modest pump depletion effects on the Raman backscattered signal, a beneficial normalisation protocol was identified. During discussions the possible limitation imposed by the weaker backscattered Raman signal towards achieving any better results on the strain and spatial resolution values, seemed to emerge. In order to enhance the performance of the sensor, anti Stokes Brillouin, which is a stronger back scattered signal, was exploited for the time domain reflectometry measurements. This resulted in 22με of temperature compensated strain resolution with a spatial resolution capability of 10cms. Although the combined performance of the Brillouin frequency in combination with Brillouin intensity proved better than the performance of the Brillouin frequency in combination with Raman intensity, but since the electronic detection system was changed together with pulse widths between the two techniques that it was unclear as to which combinatory technique was best suited for designing the sensor. It is with this view that a theoretical analysis on the performance of the R-OTDR and B-OTDR was carried under similar sensor parameters. B-OTDR is identified as a better technique compared to the R-OTDR towards providing high spatial resolution temperature compensation feature to the Brillouin frequency based distributed strain measurements. The exploration also gave an opportunity to experimentally study for the first time the impact of simultaneously varying temperature and strain on the four Brillouin coefficients. This study proved useful in identifying the corrections to the Brillouin coefficients in order to estimate the true value of strain and temperature in a temperature controlled variable strain environment. The thesis culminates with a summary of work, discussing the thresholds of various non linear effects together with means to improve the performance of the sensor. With the view of enhancing the sensor applicability, schemes of loss compensation are also discussed. In conclusion work for the future is highlighted.

The work presented in this thesis, investigating two novel optical fibre sensor systems, was carried out as part of industrially sponsored (Radiodetection Ltd) and supported applied research project. The first sensor determines the longitudinal position of acoustic disturbances acting on an extended length of optical fibre cable and the second system locates the lateral position of a buried dielectrically-sheathed fibre cable. The second system is believed to be the first optically-based sensor for the location of buried fibre optic cables. An RF electromagnetic field, emitted from above the cable, radiates through the ground and modulates the polarisation state of the light guided by the optical fibre, via the Faraday effect. The lateral position of the buried cable can then be inferred by observing the peak in the amplitude of modulation as the locator is traversed across the buried position of the fibre allowing, for the first time, dielectrically-sheathed optical cables to be located non-intrusively.

There is an ever increasing requirement for rapid sensing mechanisms for a variety of purposes – from blood analysis to gas detection. In order to allow large throughput, these devices must also be available at low cost per unit. One method which meets these criteria is the interfacing of biological and nano-scale semiconductor elements. Using modern CMOS processing, alongside further post processing, such devices can be created for a variety of purposes. However, development of these devices is expensive and in order to investigate possible structures, a simulation system is ideal. This work details the development, testing and utilisation of such a system. By combining two widely understood simulation methods – Brownian dynamics and drift diffusion – a mix of efficiency and accuracy is achieved. The introduction begins with a section detailing background to the field in order to set the work in context. The development and strict testing regime employed is then described. Initial simulations of a bio-nano interface are then presented with detection of ions though alterations in the drain current of a nominal 35 nm FET. This shows that there is a 5 nA/µm increase in drain current when an ion is moved through a 3 nm lipid layer which is suspended 15 nm above the oxide allowing identification of the period of traversal of the lipid layer. The final chapter indicates the successful detection of individual ions traversing a nano-pore in the presence of biologically significant ionic concentrations. The rate of change of drain current in the FET indicates a 4 σ signal during traversal with a background concentration of ions of 1 mM which allows clear identification of this individual event.

In this thesis the study of a multiplexed Fibre Optic Acoustic Sensor (FOAS) system is presented. Narrowband reflectors (Fibre Bragg Gratings or FBGs) define sensing sections of 12.5 metres, which then act as Fabry-Perot (FP) cavities. Low-coherence interferometry is used to interrogate the sensors with an accuracy of 50 µrad/√Hz, in good agreement with the theoretically predicted value. Heterodyne signal processing is used to eliminate low frequency environmental noise. The performance of the sensor is checked by a sinusoidal calibration signal generated by a PZT fibre stretcher. The sensor has a flat frequency response at 10 kHz with a high sensitivity of 50 µrad/√Hz and a dynamic range of 80 dB. The use of FBG based interferometers allows the use of Wavelength Division Multiplexing (WDM) technology allowing us to multiplex large number of sensors in the system. The sensing system uses Amplified Spontaneous Emission (ASE) sources for illumination purposes. ASE sources are an attractive option for interrogating arrays of FBG sensors. The coherence features of broadband ASE light makes it attractive to be used in sensing applications, since Coherence Multiplexed (CM) systems interrogated with these sources do not suffer from phase induced intensity noise, which is a problem when employing laser sources. It is well known that ASE sources suffer from excess photon noise, which is the dominant type of noise and hence limits the systems sensitivity. To get an idea of the impact of this type of noise on the performance of the system, the noise properties have been studied in detail both theoretically and experimentally. Noise spectra are calculated from the autocorrelation function of the output detector current for a thermal-like source. It is well known that unbalanced interferometers (with delay time T) act as filtering elements and produce a noise spectrum with peaks at integer multiples of 1/T, due to filtered source intensity noise. The noise analysis is used to evaluate the performance of the sensor system, and to calculate the optimum reflectivity of both FBGs in the FP sensing cavity. Optimum reflectivities for both FBGs in the FP sensors have been found. Theoretical calculations show that the best phase resolution and visibility is obtained for R1 = 40 % and R2 = 100 %. This has been verified with experiments. We also established the robustness of the system to FBG drift. A first demonstration of a FOS interrogation system using a low-coherence ASE source with a Semiconductor Optical Amplifier (SOA) is presented. The SOA is Gain-Saturated and thereby reduces the dominant intensity noise originating from the ASE source, improving the systems Signal to Noise Ratio (SNR).

Dissertação de Mestrado Integrado em Medicina Veterinária
A captura do polvo-comum (Octopus vulgaris) em Cascais tem importância económica por ser uma das espécies mais pescadas e ali vendidas. A segurança alimentar e a saúde humana dependem da qualidade e salubridade dos alimentos, tendo cada vez maior impacto na sociedade actual. Estas realidades associadas ao trabalho desenvolvido pela autora como Inspectora Sanitária na Lota de Cascais levaram à elaboração da presente dissertação. A análise sensorial é uma forma satisfatória de determinar o grau de frescura do pescado. Na UE o método mais utilizado para avaliar a categoria de frescura do pescado é baseado em tabelas de cotação de frescura adaptadas por grupos de produtos. O grupo dos cefalópodes está representado pelo choco e os parâmetros a avaliar não são os mais indicados para o polvo-comum. O objectivo do presente trabalho foi o de avaliar a qualidade microbiológica e química do polvo-comum e a sua frescura mediante a aplicação do Quality Index Method (QIM) adaptado ao polvo por Vaz-Pires & Barbosa (2004). Comparou-se a qualidade do polvo em função do método de abate e do momento de venda relativamente ao de captura. Os resultados permitem concluir que o polvo-comum capturado e vendido em Cascais é de elevada qualidade.
ABSTRACT - STUDY OF QUALITY OF COMMON OCTOPUS (Octopus vulgaris) CAUGHT IN CASCAIS BAY - The capture of common octopus (Octopus vulgaris) in Cascais has a big economic importance in this area because it is one of the main species caught and sold. Food safety and human health depends on the quality of food and has an increasing impact on society. These realities associated with the work of the author as Sanitary Inspector in Cascais led to the preparation of this dissertation. Sensory analysis is a satisfactory way to determine fish freshness. In EU the most widely used method to evaluate fish freshness is based on tables of freshness quotation adapted to different products. The group of cephalopods is represented by the cuttlefish and the parameters to evaluate are not the most suitable for common octopus. The purpose of this study was to evaluate the microbiological and chemical quality of common octopus and its freshness through the application of Quality Index Method (QIM) adapted to octopus by Vaz-Pires & Barbosa (2004). We compared the quality of octopus in relation to the method of slaughter and the time of sale after catch. The results indicate that the common octopus caught and sold in Cascais has a high quality.

In recent years there has been an increasing interest in analysis and identification of complex molecules for the medical diagnostics, pharmaceutical research and homeland security applications. If these molecules are present in high concentration, a technique known as Raman spectroscopy can be utilized. Unfortunately, only one in every 1012 photon incidence on molecule undergoes Raman scattering resulting in weak Raman absorption. An efficient technique to overcome this limitation is to utilize surface-enhanced Raman scattering (SERS) whereby molecules are placed on the surface of nanostructured metallic substrate which performs the function of transducting photons into and out of the molecules. SERS extends the scope of Raman scattering to detect molecules at low concentrations to few/single molecule level. Previously the ‘KlariteTM’ substrate consisting of an inverted array of square based pyramidal nanostructures patterned onto a Silicon substrate has been demonstrated to afford highly reproducible SERS signals with approximately 107 enhancement factor. In this report, the effect of geometrical parameters associated with the inverted pyramidal array on SERS effect for sensing applications was investigated. Geometrical parameters studied include pitch length, pit size, aspect ratio of the base of pyramid and fill factor. 3D computational modelling based on Rigorous Coupled Wave Analysis (RCWA) is used to bridge with theory. From these observations, the geometrical parameters of inverted pyramid nanostructures have been optimized for better sensing ability. A test chip is fabricated for the purpose of performing a matrix experiment, allowing deconvolution of geometrical variables: lattice pitch (1000nm-3000nm), pit size (500nm-2500nm), pit aspect ratio [width to length]. Fabrication steps include electron-beam lithography, anisotropic wet etching and metallization. Computational and experimental reflectometry systems were applied to enable the identification and analysis of a variety of dispersive features including propagating surface plasmons, localized surface plasmons and diffraction dispersion. From the study of inverted pyramid, plasmonic behaviors are observed: 1. the surface plasmon polariton depends strongly on polarization. 2. Highly dispersive features arising from simple surface diffraction effects appear insensitive to polarization state. 3. As the pit size gets bigger, the diffraction efficiency decreases but the wavelength/angular position remain the same. 4. Diffractive features are relatively sharp and clearly defined (narrow bandwidth), and are highly dependent on lattice pitch. Hence they move in wavelength and angle (e.g. highly dispersive) as pitch is varied. These features relate to the coupling of light into or out of the sensor chip. 5. Localized surface plasmons have characteristic of small wavelength shift over wide angular range (low dispersion), and are generally broader in bandwidth. Plasmon features can conclusively be identified over diffractive features by making comparisons between simulations ‘with’ and ‘without’ the top metal coating. In order to derive the optimal geometry for SERS sensor, a highly stable test molecule which is known to form a monolayer coating on gold is required. For this purpose benzenethiol was used as standard in this work. Devices were tested using a Renishaw Invia Raman system. The main wavelength of interest here is 785nm where this laser is readily available and compatible with the end user Raman system. Full details of the optical and Raman measurements are carried out on the silicon test platform. Results show that the averaged SERS enhancement factor was only slightly dependent upon lattice pitch, but was highly dependent on pit size and aspect ratio. Density of the pits plays a further role simply by increasing the number of pits/unit area and so provides extra increase in SERS signal. The experimental data shows this is not simply a surface area dependent effect, but the optimal SERS signal can be obtained by close packing as tightly as possible pits of the optimal size. Minimum spacing (between adjacent pits) of 250nm is found to give the highest SERS enhancement. The optimal aspect ratio was found to be 1:1.2 and the optimal pit size determined to be 1000nm. This new optimized design shows 10-fold improvement in sensitivity compared to current available benchmark Klarite. The study has also explored the possibility of replicating the optimized design to a cost effective and disposable polymer for the purpose of mass production. This was carried out using nanoimprint lithography. The replicated plastic sensor is comparable to the benchmark silicon Klarite. As a proof of principle, the qualitative performance in two demonstrator molecules such as ibuprofen and melamine has been carried out. The disposable plastic sensor was demonstrated for the possibility of dual sensing mechanisms such as surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS). The sensitivity of plastic sensor using SPR mechanism is 225.83nm/RIU on thiol molecule. The work has also been carried out for an alternative SERS sensor design by changing the sidewall profile to 90˚ angle from (100) silicon etched plane. Changing the sidewall profile makes impact on the plasmonic behaviour. The straight sidewalls are favourable to the localized plasmon mode. The structures with slope sidewalls are favourable to both localized and propagating plasmons inside the cavities. This work was conducted as part of the FP7 ‘’PHOTOSENSE’’ consortium project.

Airborne CW doppler proximity sensors are very sensitive, but leaks precise height measurement. It may be possible to estimate the heigth at the terminal phase (the case where the sensor is at a heigth close to ground) precisely by using the doppler shift and amplitude information. The thesis includes this novel concept with theoritical analysis and simulation results.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California
This paper overviews the High Explosive Radio Telemetry (HERT) system, under co-development by Los Alamos National Laboratories and AlliedSignal Federal Manufacturing & Technologies. This telemetry system is designed to measure the initial performance of an explosive package under flight environment conditions, transmitting data from up to 64 sensors. It features high speed, accurate time resolution (10 ns) and has the ability to complete transmission of data before the system is destroyed by the explosion. In order to affect the resources and performance of a flight delivery vehicle as little as possible, the system is designed such that physical size, power requirements, and antenna demands are as small as possible.

In this thesis, the design, fabrication and characterisation of a bio-inspired microelectromechanical systems (MEMS) based tactile sensor array is presented. A vast amount of research has been carried out in the area of tactile sensing and various transduction methods have been explored. However, currently no device exists with a performance comparable to that of the biological tactile sensors of the human fingertip in terms of robustness, sensitivity, spatial resolution and dynamic performance. The sensors developed in this work employ the principles of electrical capacitance and are fabricated from commercially available siliconon- oxide wafers using simple process steps. Each sensor is formed from two plates of highly conductive silicon separated by an air-gap formed from sacrificial etching of the oxide layer. Deflection of the 2 \(\mu\)m thick upper plate of the sensor as a result of applied mechanical stimulus, causes a change in capacitance which is the output of the sensor. Within the array, the individual sensors are spaced 150 \(\mu\)m apart (centre-centre pitch of 570 \(\mu\)m) and therefore offer the potential for high spatial resolution. To protect the sensor array from mechanical shock and provide skin like compliance, the use of suitable packaging materials was explored. The use of poly dimethyl siloxane (PDMS) as a suitable skin-like material was demonstrated. Modification of the surface topography of the packaging layer to include ’fingerprint’ like features was explored and its benefits highlighted. Sensor characterisation experiments revealed that the sensing device was sufficiently sensitive to allow the discrimination of different textures (with feature spacing down to 0.2 mm) through tests conducted using gratings varying in spatial periodicity and fabrics. Based on the results, the sensors can be used as an analogue of the slowly adapting tactile receptors (Merkel disks) for robotic finger applications.

L’obésité et les maladies cardiométaboliques sont des problèmes de santé publique dans les populations nordiques du Canada ainsi qu’à travers le monde. Il est actuellement proposé que l’augmentation de ces désordres est en partie causée par divers facteurs environnementaux qui génèrent des changements importants du microbiote intestinal. Cette communauté microbienne qui peuple notre tractus gastrointestinal joue un rôle clé dans le métabolisme de nutriments, mais peut aussi avoir des effets néfastes lorsque son équilibre avec l’hôte est perturbé. Cette compréhension a mis en évidence le manque d’outils prédictifs permettant un diagnostic rapide et efficace dans le domaine biomédical. L’analyse actuelle du microbiote est réalisée à posteriori au niveau des selles, ce qui requiert du personnel hautement qualifié de même que des procédures longues et dispendieuses. L’objectif de ce projet est de concevoir un capteur optique qui, une fois implanté dans l’intestin, permettra de détecter en temps réel des biomarqueurs clés produit par le microbiome intestinal. Dans le cadre d’une preuve de concept, une architecture fibrée simple permettant de mesurer quantitativement des variations de pH est démontrée. Contrairement aux capteurs fibrés traditionnels, la sonde optique de ce projet exploite l’onde évanescente générée sur la périphérie de l’interface pour exciter des nanomatériaux greffés dont les propriétés de fluorescence varient selon leur environnement chimique. Les mesures sont possibles grâce à un système optique mobile contrôlé par un logiciel convivial qui permet à un utilisateur nonexpert d’utiliser l’appareil. Les résultats confirment qu’avec un étalonnage préalable il est possible avec cette sonde modèle de prendre des mesures quantitatives du pH en temps réel in vitro. Les expériences préliminaires suggèrent que la sonde permet aussi de mesurer le pH en temps réel dans l’intestin in vivo.
L’obésité et les maladies cardiométaboliques sont des problèmes de santé publique dans les populations nordiques du Canada ainsi qu’à travers le monde. Il est actuellement proposé que l’augmentation de ces désordres est en partie causée par divers facteurs environnementaux qui génèrent des changements importants du microbiote intestinal. Cette communauté microbienne qui peuple notre tractus gastrointestinal joue un rôle clé dans le métabolisme de nutriments, mais peut aussi avoir des effets néfastes lorsque son équilibre avec l’hôte est perturbé. Cette compréhension a mis en évidence le manque d’outils prédictifs permettant un diagnostic rapide et efficace dans le domaine biomédical. L’analyse actuelle du microbiote est réalisée à posteriori au niveau des selles, ce qui requiert du personnel hautement qualifié de même que des procédures longues et dispendieuses. L’objectif de ce projet est de concevoir un capteur optique qui, une fois implanté dans l’intestin, permettra de détecter en temps réel des biomarqueurs clés produit par le microbiome intestinal. Dans le cadre d’une preuve de concept, une architecture fibrée simple permettant de mesurer quantitativement des variations de pH est démontrée. Contrairement aux capteurs fibrés traditionnels, la sonde optique de ce projet exploite l’onde évanescente générée sur la périphérie de l’interface pour exciter des nanomatériaux greffés dont les propriétés de fluorescence varient selon leur environnement chimique. Les mesures sont possibles grâce à un système optique mobile contrôlé par un logiciel convivial qui permet à un utilisateur nonexpert d’utiliser l’appareil. Les résultats confirment qu’avec un étalonnage préalable il est possible avec cette sonde modèle de prendre des mesures quantitatives du pH en temps réel in vitro. Les expériences préliminaires suggèrent que la sonde permet aussi de mesurer le pH en temps réel dans l’intestin in vivo.
Obesity and cardiometabolic diseases (CMD) are major public health issues among Canada’s northern population and throughout the world. It is believed that the exponential rise in CMD incidence is due to numerous environmental factors, which are driving important changes in the gut microbiome. This microbial community which populates our intestinal tract plays a key role in nutrient and energy metabolism, but can also drive pathogenic mechanisms when its interaction with the host is disrupted. This understanding has highlighted the lack of predictive tools and biomarkers for rapid and efficient diagnostic of various diseases within the medical field. Current analysis of the gut microbiota is mostly based on sequencing technologies to determine microbial composition and gene expression, while functional analyses are limited to surrogate markers of microbial activities through stool metabolites. The goal of this study is to develop a “Sensor-in-Fibre” probe with the capacity to detect key microbiome-derived molecules relevant to CMD pathogenesis in real time in vivo. The optical probe takes advantage of evanescent fields generated on its peripheral interface to excite species-selective surface-grafted sensing nanomaterials that have varying fluorescent properties based on the target molecules present in the surrounding environment. As a model system, FITC functionalized with (3-aminopropyl)triethoxysilane was grafted on the periphery of an optical fiber, leading to qualitative pH measurements revealed through fluorescence emission qualities. These measurements are possible due to the use of a mobile signal collection apparatus in conjunction with custom software made to enable a non-expert technician to use it. The experimental results demonstrate that, with the appropriate preparation, it is possible to quantitatively measure pH with this probe structure in vitro and preliminary studies suggest that the probe is also capable of measuring pH in vivo in real time.
Obesity and cardiometabolic diseases (CMD) are major public health issues among Canada’s northern population and throughout the world. It is believed that the exponential rise in CMD incidence is due to numerous environmental factors, which are driving important changes in the gut microbiome. This microbial community which populates our intestinal tract plays a key role in nutrient and energy metabolism, but can also drive pathogenic mechanisms when its interaction with the host is disrupted. This understanding has highlighted the lack of predictive tools and biomarkers for rapid and efficient diagnostic of various diseases within the medical field. Current analysis of the gut microbiota is mostly based on sequencing technologies to determine microbial composition and gene expression, while functional analyses are limited to surrogate markers of microbial activities through stool metabolites. The goal of this study is to develop a “Sensor-in-Fibre” probe with the capacity to detect key microbiome-derived molecules relevant to CMD pathogenesis in real time in vivo. The optical probe takes advantage of evanescent fields generated on its peripheral interface to excite species-selective surface-grafted sensing nanomaterials that have varying fluorescent properties based on the target molecules present in the surrounding environment. As a model system, FITC functionalized with (3-aminopropyl)triethoxysilane was grafted on the periphery of an optical fiber, leading to qualitative pH measurements revealed through fluorescence emission qualities. These measurements are possible due to the use of a mobile signal collection apparatus in conjunction with custom software made to enable a non-expert technician to use it. The experimental results demonstrate that, with the appropriate preparation, it is possible to quantitatively measure pH with this probe structure in vitro and preliminary studies suggest that the probe is also capable of measuring pH in vivo in real time.
Résumé en espagnol
Résumé en espagnol

In industrial drives market, speed and position estimation are one of the most important subjects for accurate motor drives. Vector controlled drives has the best dynamic performance among AC motor drives. Sensorless vector control is one of the most studied one. However, sensorless drive systems fail at low or zero speeds and may not have enough accuracy. For better accuracy and speed range speed sensors or position encoders are usually essential. However, coupling of sensor and sensor prices introduces extra cost on the drive. Thus in order to reduce the cost of the drive a cheap and easy to mount speed sensor is essential. Throughout this study, a speed and position sensor using an external search coil placed between cooling fins on the frame of an induction machine is proposed. The search coil utilizes the fringing flux outside the frame of induction motor. Using the induced voltage on the external search coil, a new method that estimates the flux and rotor position is proposed. In this study, the induced voltage on the search coils are investigated with different types of search coils placed on various positions. The frequency domain and time domain analysis are performed in order to build a model that can estimate machine flux, rotor speed and rotor position. As a result of this study, a low cost, easy to mount speed and position sensor is designed and implemented. Experiment results are presented.