A proposta deste trabalho é a produção de matrizes de nanotubos de dióxido de titânio seguindo os métodos de anodização eletroquímica de titânio estabelecidos da literatura. O objetivo central é a compreensão aprofundada das etapas do processo de crescimento dos nanotubos de TiO2, para posterior otimização de sua síntese visando as diferentes aplicações. Com este propósito foram realizados sistematicamente os seguintes estudos: das diferentes fases de crescimento dos nanotubos de TiO2, do efeito dos diferentes parâmetros de anodização na morfologia dos nanotubos e da reprodutibilidade dos processos. Visando as diferentes aplicações foram estudados métodos para obtenção de membranas autossustentadas e remoção de nanoresíduos. O método de camada sacrificial de fotoresiste positivo apresentou melhor resultado para remoção de nanoresíduos do topo dos nanotubos de TiO2 do que as demais técnicas. Por último, os arranjos obtidos com esta método foram aplicados na fabricação dos sensores de pH. / This work proposes the production of titania nanotubes arrays following the electrochemical anodization methods of a titanium sheet established in the literature. The main goal is a deep comprehension of the different TiO2 nanotubes growth stages for further optimization aiming the diverse applications. In this way the following systematic studies were performed: of the initial growth stages, of the effect of each anodization parameter on the nanotubes morphology and of the process reproducibility. In addition, methods for the production of self-sustained membranes as well as for obtaining a nanotube array surface free of nanoremnants were studied aiming the different applications. Positive photoresist bases sacrificial layer method presented a better result to eliminate nano-remnants on top of TiO2 nanotubes than other techniques. Finally, the nanotubes arrays obtained with this method were utilized for pH sensors fabrication.

The use of wearable sensors in consumer health and medicine is a rapidly developing topic of interest. The main purpose of the series of studies in this thesis is to identify novel uses of technology that can provide clinicians and scientists clinically feasible, low cost approaches to obtain meaningful information about functional limb symmetry in patients with knee injuries. In Study 1, individuals undergoing knee surgery were evaluated as they walked and stepped down onto a force platform in a manner similar to how one would step off a curb to cross a street. When subjects stepped onto their uninvolved leg, peak vertical ground reaction force was greater and occurred earlier than when stepping onto their involved leg. Asymmetries were greater in those with higher quadriceps neuromuscular impairment. In Study 2, the reliability and validity of using wearable accelerometer sensors was evaluated for estimating single leg vertical hop height in healthy people and individuals after ACL reconstruction surgery. The reliability and concurrent validity of using accelerometers to estimate single leg hop height were excellent, and were similar for healthy and ACL-reconstructed subjects. Error for this method was low, in particular when the accelerometer was worn at the lower leg. Asymmetry in hop height was greater in those with higher quadriceps neuromuscular impairment. In Study 3, wearable accelerometers were compared to a system of motion capture cameras and force platform as a method to assess functional movement asymmetry in healthy people and individuals after ACL reconstruction. While walking and stepping down, accelerometers worn at the waist were able to detect underlying movement asymmetry when it exists in people after ACL reconstruction. Acceleration at the waist was strongly associated with vertical ground reaction force and moderately associated with knee extension moments. Collectively, these studies provide evidence that functional movement symmetry can be measured with simple, inexpensive methods that can be used in a variety of clinical or field-based settings.

Noninvasive glucose monitoring has been the subject of considerable research because of the high number of diabetes patients who must monitor their glucose levels daily by taking blood samples. Among methods being evaluated for possible use in this application, near-infrared (NIR) spectroscopy has received significant attention because of available glucose absorption bands that can be observed in the presence of the large aqueous background found in tissue spectra. The objective of the research presented here is to evaluate the potential for implementing a noninvasive nocturnal hypoglycemic alarm with NIR spectroscopy. Such an alarm would be used by a diabetic to detect potentially dangerous occurrences of hypoglycemia during sleep. The approach used is to collect spectra continuously from the patient during the sleep period, followed by the application of pattern recognition methods to determine if a spectrum represents a blood glucose level that exceeds a hypoglycemic threshold. A reference spectrum is collected and a conventional finger-stick glucose concentration measurement is made at the start of the sleep period. The ratio is then taken of each subsequent spectrum to the collected reference, forming a differential spectrum corresponding to the signed difference in concentration relative to the reference. The identification of these differential spectra as "alarm" or "non-alarm" is performed with a classification model computed with piecewise linear discriminant analysis. This methodology is initially tested with in vitro laboratory data that simulated the glucose excursions that occur during sleep. The performance of the hypoglycemic alarm methodology in the presence of varying levels of urea, glyceryl triacetate, and L-lactate as potential spectral interferents is tested. The robustness of the methodology with respect to time is also evaluated. The thesis further discusses an experimental procedure to prepare tissue phantoms composed of two main proteins that exist in human skin tissue, keratin and collagen. A new methodology is developed to produce varying-thickness films that allowed the simulation of changes in the content of skin tissue proteins present within the optical path of the NIR measurement. The prepared films are incorporated into in vitro laboratory measurements in which varying levels of glucose, urea, keratin, and collagen are introduced in order to provide a test of the hypoglycemic alarm algorithm that simulates the spectral properties of human tissue. Finally, the hypoglycemic alarm algorithm is tested with in vivo data collected with rat animal models. Data are presented for single-day experiments performed with anesthetized rats, as well as for multiple-day experiments conducted with awake rats. The results obtained from both the in vitro and in vivo studies confirm that if high-quality spectral data are attainable, the alarm methodology can work effectively to identify hypoglycemic events while exhibiting a low rate of false detections.

Wearable sensors are at the heart of the digital health revolution. Integral to the use of these sensors for monitoring conditions impacting balance and mobility are accurate estimates of joint angles. To this end a simple and novel method of estimating hip joint angles from small wearable magnetic and inertial sensors is proposed and its performance is established relative to optical motion capture in a sample of human subjects. Improving upon previous work, this approach does not require precise sensor placement or specific calibration motions, thereby easing deployment outside of the research laboratory. Specific innovations include the determination of sensor to segment rotations based on functionally determined joint centers, and the development of a novel filtering algorithm for estimating the relative orientation of adjacent body segments. Hip joint angles and range of motion determined from the proposed approach and an existing method are compared to those from an optical motion capture system during walking at a variety of speeds and tasks designed to exercise the hip through its full range of motion. Results show that the proposed approach estimates flexion/extension angle more accurately (RMSE from 7.08 to 7.29 deg) than the existing method (RMSE from 11.64 deg to 14.33 deg), with similar performance for the other anatomical axes. Agreement of each method with optical motion capture is further characterized by considering correlation and regression analyses. Mean ranges of motion for the proposed method are not largely different from those reported by motion capture, and showed similar values to the existing method. Results indicate that this algorithm provides a promising approach for estimating hip joint angles using wearable inertial sensors, and would allow for use outside of constrained research laboratories.

Les capteurs sont des dispositifs ayant montré une utilisation répandue, allant de la détection des molécules en phase gazeuse au suivi de signaux chimiques dans les cellules biologiques. En général, un capteur est réalisé à partir d’un élément actif de détection et d’un signal transducteur produisant un signal de sortie qui peut être électrique, optique, thermique ou magnétique. Les électrodes à base de nanotubes de carbone à simple paroi et les électrodes à base de graphène se sont révélées être un matériau excellent pour le développement des biocapteurs électrochimiques, puisqu’ils montrent des propriétés électroniques remarquables et la capacité de se comporter en tant que nano-électrodes individuelles, un excellent transport de porteur de charge à faible dimension, et permettent de l’électrocatalyse de surface. Le travail présenté vise à la préparation et à l’étude d’électrodes de nanotubes de carbone à simple paroi et d’électrodes de graphène modifiées par voie électrochimique pour des applications dans le domaine des biocapteurs. Nous avons d’abord étudié les films de nanotubes de carbone à simple paroi et nous nous sommes intéressés à leur topographie, à leur composition de surface, et leurs propriétés électriques et optiques. Nous montrons que ces films sont homogènes avec une conductivité d’environ 200-300 Ω/□, et une transparence d’environ 40%. En parallèle aux nanotubes de carbone à simple paroi, des films de graphène ont été étudiés. Des valeurs de résistance plus élevées en comparaison avec les films de nanotubes ont été obtenues. La modification de surface par voie électrochimique des deux types d'électrodes a été étudiée en suivant deux voies, (i) l’électro-greffage de sels d’aryl diazonium, et (ii) l’addition électrophile de 1, 3- benzodithiolilyumtetrafluoroborate (BDYT). Les caractéristiques qualitatives et quantitatives de la surface modifiée des électrodes ont été étudiées, comme le degré de fonctionnalisation et la composition de surface. La combinaison de spectroscopie Raman, et de photoelectrons X- (XPS) de microscopie à force atomique (AFM),d'électrochimie et d’autres techniques, a montré que des précurseurs particuliers peuvent être ancrés de façon covalente à la surface des électrodes de nanotubes etde graphène, grâce à la formation de nouvelles liaisons carbone-carbone. Dans le premier cas (i), leur post-modification par des réactions de « clickchemistry» mène finalement à l’immobilisation sur la surface de l’électrode des groupes fonctionnels souhaités, comme des sondes/shuttles redox (e.g., un groupeferrocenyl) ou des groupements catalytiques (e.g., une enzyme). L'enzyme HRP(horse-radish peroxidase) a été, par exemple, immobilisée sur des surfaces de nanotubes de carbones à simple paroi modifiées par un groupe aryl, et l'étude voltammétrique a montré une réponse catalytique avec l’augmentation de la concentration de peroxyde d’hydrogène en solution, en suivant le « shuttle » redoxhydroquinone/benzoquinone à la surface de l’électrode. Dans le second cas (ii), l’addition électrophile de radicaux BDYT électro-générés a été étudiée pour la première fois sur des électrodes de nanotubes de carbone à simple paroi ou sur les électrodes de graphène. La combinaison de différentes techniques complémentaires a montré l’attachement covalent de BDYT aux électrodes de nanotubes de carbone à paroi simple. Une telle modification mène à la formation de rubans torsadés qui ont pu être observés et analysés par AFM et parmicroscopie électronique à balayage. Aucune preuve de la formation de rubans torsadés n’a pu être mise en évidence pour les électrodes modifiées à base de graphène. / Sensors are devices that have shown wide spread use, from the detection of gas molecules to the tracking of chemical signals in biological cells. In general, a sensor is made of an active sensing element and a signal transducer producing an electrical,optical, thermal or magnetic output signal. Single walled carbon nanotube (SWCNT) and graphene based electrodes have demonstrated to be an excellent material for the development of electrochemical biosensors as they display remarkable electronic properties and the ability to act as individual nanoelectrodes, display an excellent low-dimensional charge carrier transport, and promote surface electrocatalysis. The present work aims at the preparation and investigation of electrochemically modified SWCNT and graphene-based electrodes for applications in the field of biosensors. We initially studied SWCNT films and focused on their topography and surface composition, electrical and optical properties. We show that these films are homogeneous with thickness around 6̴ 0-70 nm, resistance values around 2̴ 00-300Ω/□, and transparency around 4̴ 0%. Parallel to SWCNTs, graphene films were investigated. Higher resistance values were obtained in comparison with nanotubes films.The electrochemical surface modification of both electrodes was investigated following two routes (i) the electrografting of aryl diazonium salts, and (ii) the electrophylic addition of 1, 3-benzodithiolylium tetrafluoroborate (BDYT). Both the qualitative and quantitative characteristics of the modified electrode surfaces were studied such as the degree of functionalization and their surface composition. The combination of Raman, X-ray photoelectron spectroscopy, atomic force microscopy, electrochemistry and other techniques, has demonstrated that selected precursors could be covalently anchored to the nanotubes and graphene-based electrode surfaces through novel carbon-carbon formation. In route (i), their post-modification by click-chemistry reactions finally leads to the immobilization at the electrode surface of desired functional groups, such as redoxprobes/shuttles (e.g., a ferrocenyl group) or catalytic moieties (e.g., an enzyme).HRP has been for instance immobilized on SWCNT-aryl-modified surfaces, and its voltammetric study showed catalytic response with the increasing concentration of hydrogen peroxide in solution upon monitoring the redox shuttlehydroquinone/benzoquinone at the electrode surface. In route (ii), the electrophylic addition of electrogenerated BDYT radicals was investigated for the first time at either SWCNT- or graphene-based electrodes. The combination of different techniques has demonstrated the covalent attachment of BDYT to SWCNT-based electrodes. Such modification leads to the formation of twisted ropes observed and analyzed by AFM and scanning electron microscopy. No evidence of twisted ropes formation was instead observed for modified graphene based electrodes.

Building smart home environments which automatically or semi-automatically assist and comfort occupants is an important topic in the pervasive computing field, especially with the coming of cheap, easy-to-install sensors. This has given rise to the indispensable need for human activity recognition from ubiquitous sensors whose purpose is to observe and understand what occupants are trying to do from sensory data. The main approach to the problem of human activity recognition is a probabilistic one so as to handle the complication of uncertainty, the overlapping of human behaviours and environmental noise. This thesis develops a probabilistic model as a framework for human activity recognition using multiple multi-modal sensors in complex pervasive environments. The probabilistic model to be developed is adapted and based on the abstract hidden Markov model (AHMM) with one layer to fuse multiple sensors. The concept of factored state representation is employed in the model to parsimoniously represent the state transitions for reducing the number of required parameters. The exact method is used in learning the model’s parameters and performing inference. To be able to incorporate a large number of sensors, several more parsimonious representations including the mixtures of smaller multinomials and sigmoid functions are investigated to model the state transitions, resulting in a reduction of the number of parameters and time required for training. / We examine the approximate variational method to significantly reduce the time required for training the model instead of using the exact method. A system of fixed point equations is derived to iteratively update the free variational parameters. We also present the factored model in the case where all variables are continuous with the use of the conditional Gaussian distribution to model state transitions. The variational method is still employed in this case to speed up the model’s training process. The developed model is implemented and applied in recognizing daily activity in our smart home and the Nokia lab from multiple sensors. The experimental results show that the model is appropriate for fusing multiple sensors in activity recognition with a reasonable recognition performance.

Breathing Stabilization System is a new idea and method. The purpose of this system is to produce a device to control a patient's breathing for gated radiotherapy. This thesis focuses on building a simple Breathing Stabilization System that includes five solenoids, a power supply and five force sensors to build up the whole system. Significantly, this thesis will introduce the modeling of solenoids in detail that include how to build a mathematical model of the solenoids. The simulation of the electromagnetic in professional multi-physics software COMSOL will also be explained. To drive the solenoid system, a voltage-to-current converter is used. This part will be introduced as well as the operational amplifier circuit used by the force sensors.

A measurement system has been developed for use on a light aircraft to measure the pressure distribution over the wing surfaces. The measurement system was developed as a low-cost alternative to existing advanced measurement systems. The system consisted of low profile, low cost pressure sensors that interfaced digitally with microcontrollers for data acquisition. The pressure sensors and microcontrollers were developed into self-contained sensor modules with all electronic components mounted on flexible circuit board that formed the base of the modules. Two types of module were developed; a module with a single pressure sensor and a module with a row of seven pressure sensors at fifteen millimetre spacing. The total cost of the sensor modules was approximately ninety dollars for a single sensor module and one hundred and forty dollars for the seven sensor module. Studies were carried out using numerical methods to predict the pressure distribution over a NACA2412 airfoil. The numerical studies were used to evaluate the effect of adding the sensor modules to the wing, and the effect of the sensor distribution on measured force coefficients. Numerical predictions were made using the XFOIL software package. This software was validated using the Hess-Smith inviscid panel method. Flight testing was carried out with the pressure distribution measurement system to confirm the operation of the system and to make preliminary measurements. The flight testing focused on the measurement of steady state pressure distributions for comparison with the numerical predictions. Good agreement was found between the measured pressure distributions and the XFOIL predictions. Integration of the pressure distributions enabled comparison of normal force, lift force and quarter chord moment coefficients. The measured force coefficients showed the expected trends with angle of attack although it was found that the limited number of sensor modules used caused large error in the quarter chord moment coefficient compared to the numerical predictions.

In this thesis, the author proposes and presents a novel simulation technique for the analysis of multilayered Flexural Plate Wave (FPW) devices based on the convergence of the Finite Element method (FEM) with classical Surface Acoustic Wave (SAW) analysis techniques and related procedures. Excellent agreement has been obtained between the author's approach and other more conventional modelling techniques. Utilisation of the FEM allows the performance characteristics of a FPW structure to be critically investigated and refined before undertaking the costly task of fabrication. Based on a series of guidelines developed by the author, it is believed the proposed technique can also be applied to other acoustic wave devices. The modelling process developed is quite unique as it is independent of the problem geometry as verified by both two and three dimensional simulations. A critical review of FEM simulation parameters is presented and their effect on the frequency domain response of a FPW transducer given. The technique is also capable of simultaneously modelling various second-order effects, such as triple transit, diffraction and electromagnetic feedthrough, which often requires the application of several different analysis methodologies. To verify the results obtained by the author's novel approach, several commonly used numerical techniques are discussed and their limitations investigated. The author initially considers the Transmission Matrix method, where it is shown that an inherent numerical instability prevents solution convergence when applied to large frequency-thickness products and complex material properties which are characteristic of liquids. In addition the Stiffness Matrix method is investigated, which is shown to be unconditionally stable. Based on this technique, particle displacement profiles and mass sensitivity are presented for multilayered FPW structures and compared against simpler single layer devices commonly quoted in literature. Significant differences are found in mass sensitivity between single layer and multilayered structures. Frequency response characteristics of a FPW device are then explored via a spectral domain Green's function, which serves as a further verification technique of the author's novel analysi s procedure. Modifications to the spectral domain Green's function are discussed and implemented due to the change in solution geometry from SAW to FPW structures. Using the developed techniques, an analysis is undertaken on the applicability of FPW devices for sensing applications in liquid media. Additions are made to both the Stiffness Matrix method and FEM to allow these techniques to accurately incorporate the influence of a liquid layer. The FEM based approach is then applied to obtain the frequency domain characteristics of a liquid loaded FPW structure, where promising results have been obtained. Displacement profiles are considered in liquid media, where it is shown that a tightly coupled Scholte wave exists that is deemed responsible for most reported liquid sensing results. The author concludes the theoretical analysis with an in-depth analysis of a FPW device when applied to density, viscosity and mass sensing applications in liquid media. It is shown that a single FPW device is potentially capable of discriminating between density and viscosity effects, which is typically a task that requires a complex and costly sensor array.

The harmful effects of aircraft noise, with respect to both comfort and occupational health, have long since been recognised, with many examples of sound control now implemented in commercial aircraft. However, the single engine light aircraft cabin is still an extremely noisy environment, which apparently has been side-lined by both cost and weight constraints, especially with respect to low frequency sound reduction. Consequently, pilots and passengers of these aircraft are still exposed to potentially damaging noise levels and hearing damage can only be avoided by the proper use of ear defenders. Minimisation of the noise around the occupants of the aircraft reduces the dependency of personal ear defenders and is conducive to a more comfortable, hygienic and less stressful environment. This thesis describes the basis of a theoretical and experimental project, directed at the design and evaluation of a practical active noise control (ANC) system suitable for a single engine light aircraft. Results from initial experiments conducted in a single engine aircraft demonstrated the viability of ANC for this application. However, the extreme noise, the highly damped cabin, the multiple tone excitation, the severe weight limitations and the requirement of air worthiness certification severely complicated the problem of achieving noise reduction throughout the entire aircraft cabin. Compromising the objective to only achieving local control around the occupants still presented difficulties because the region of attenuated noise around the error sensors was so small that a nearby observer experienced no sound level reduction whatsoever. The objective was therefore to move the control zone away from the error sensor and place a broad envelope of noise reduction immediately around the occupant's head, through the use of virtual sensors , thus creating the perception of global noise control. While virtual sensors are not new (Garcia-Bonito et al. (1996)), they are currently limited to acoustic pressure estimation (virtual microphones) via the initial measurement of an observer / sensor transfer function. In this research, new virtual sensor algorithms have been developed to: 1. minimise the sound level at the observer location, 2. broaden the control region, 3. adapt to any physical system changes and 4. produce a control zone that may ultimately follow an observer's head The performance of the virtual sensors were evaluated both analytically and experimentally in progressively more complex environments to identify their capabilities and limitations. It was found that the use of virtual sensors would, in general, attenuate the noise at the observer location more effectively than when using conventional remotely placed error sensors. Such a control strategy was considered to be ideal for a light single engine aircraft, because it would only require small light speakers (possibly fitted into a head-rest) to achieve a broad control zone that envelopes the region around the occupants heads. / Thesis (Ph.D.) -- University of Adelaide, Dept. of Mechanical Engineering), 2000.