The main purpose of this thesis was to investigate and characterize the use of piezoelectric yarn for use in textile (fingertip) pressure sensors in glove applications. Such applications could include healthcare, security and safety, game applications or intelligent control. Piezoelectric materials generate a voltage when pressed or squeezed. Poly(vinylidene fluoride) (PVDF) is a polymorphic material with piezoelectric properties. PVDF yarns were integrated into block sensors. These blocks consist of thermoplastic material glued to a knitted supporting fabric. The electrical signal given off by the PVDF yarn was measured with the help of an oscilloscope. The block sensor generated a distinguishable signal under a dynamic compression of 0.003 N, indicating that the structure is sensitive enough compared to the average male fingertip sensitivity threshold (0.0054N). / Program: Master programme in Textile Engineering

A análise de um sensor óptico de pressão foi realizada neste trabalho. O sensor baseia-se no deslocamento de um diafragma composto por camadas de silício, dióxido de silício e vidro. O deslocamento do diafragma causa a alteração do índice de refração do guia óptico do ramo sensor de um interferômetro de Mach-Zehnder, formado por guias do tipo \"rib\" na camada de vidro. A diferença de fase entre os sinais ópticos dos ramos sensor e de referência causa variação da intensidade luminosa na saída deste interferômetro. A simulação do deslocamento do diafragma foi feita empregando-se o Método das Diferenças Finitas, que também foi, utilizado no cálculo da alteração do índice de refração no guia óptico. O diafragma de três camadas foi substituído, nos cálculos, por outro composto de uma camada equivalente. A análise da propagação da luz no guia tipo \"rib\" foi feita por intermédio do Método do Índice Efetivo. Para a distribuição dos campos elétrico (para o modo TE) e magnético (para o modo TM) admitiu-se uma variação gaussiana na direção y, e a formulação clássica para um guia planar assimétrico, na direção x. O resultado final deste trabalho apresentou melhor aproximação com os dados experimentais do trabalho realizado por OHKAWA [23] do que a própria previsão teórica daquele. São apresentados gráficos do deslocamento do diafragma em função da pressão aplicada, da variação do índice de refração do guia do ramo sensor em função das dimensões geométricas do guia, da distribuição da componente de campo elétrico no guia óptico em função das suas dimensões geométricas, da defasagem entre os sinais dos ramos sensor e de referência em função da pressão aplicada e da pressão de meia-onda em função do comprimento do diafragma. / An integrated optical pressure sensor was analysed in this work. The sensor is based on the deflection of a multilayered diaphragm and operates as a Mach-Zehnder interferometer. A pressure difference between the upper and lower faces of the diaphragm induces a strain and produces a refractive index change in the sensor arm of the interferometer. As a consequence, a phase-shift is established between both arms of the sensor and light intensity modulation is observed at the device output. The Finite Difference Method was used in order to calculate the diaphragm deflection and the refractive index change. In the formulation the multilayered diaphragm was replaced by a single-layered one, with an equivalent bending rigidity. The light propagation in the rib-type waveguide sensor arm was analysed by the Effective lndex Method. A gaussian variation was assumed for the y-component of the electric (TE mode) and magnetic (TM mode) field distributions. In the x-direction the classical formulation was used. Results for the diaphragm deflection dependence on the applied pressure, the refractive index change as a function of the device geometry, phase shift versus applied pressure, as well as halfwave pressure as a function of diaphragm lenght are presented. The final model yield a better agreement to experimental data than the formulations previously available in the literature.

Diamond is widely known for its extraordinary properties, such as high thermal conductivity, energy bandgap and high material hardness and durability making it a very attractive material for microelectronic and mechanical applications. Synthetic diamonds produced by chemical vapor deposition (CVD) methods retain most of the properties of natural diamond. Within this class of material, nanocrystalline diamond (NCD) is being developed for microelectronic and microelectromechanical systems (MEMS) applications. During this research, intrinsic and doped NCD films were grown by the microwave plasma enhanced chemical vapor deposition (MPECVD) method using CH4/Ar/H2 gas mixture and CH4/Ar/N2 gas chemistries respectively. The first part of research focused on the growth and characterization of NCD films while the second part on the application of NCD as a structural material in MEMS device fabrication. The growth processes were optimized by evaluating the structural, mechanical and electrical properties. The nature of chemical bonding, namely the ratio of sp²:sp³ carbon content was estimated by Raman spectroscopy and near edge x-ray absorption fine structure (NEXAFS) techniques. The micro-structural properties were studied by x-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The mechanical properties of the pure NCD films were evaluated by nano-indentation. The electrical properties of the conductive films were studied by forming ohmic as well as schottky contacts. In second part of this study, both free-standing and membrane capped field emitter devices were fabricated by a silicon mold technique using nitrogen incorporated (i.e., doped) NCD films. The capped field emission devices act as a prototype vacuum microelectronic sensor. The field emission tests of both devices were conducted using a diode electrical device model. The turn-on field and the emission current of free-standing emitter devices was found to be approximately 0.8 V/µm and 20 µA, respectively, while the turn-on fields of capped devices increased by an order of magnitude. The emission current in the field emission sensor changed from 1 µA to 25 µA as the membrane was deflected from 280 µm to 50 µm from the emission tip, respectively.

In this research, novel high resolution reinforced diaphragm MEMS piezoresistive pressure sensors were designed, fabricated and tested to measure physical phenomena (such as depth/pressure variations) in the ocean. To complement the physical sensing elements, a microfluidic electrochemical nitrate sensor, was also developed to detect chemical fluxes. The electrochemical sensor was designed and packaged to conform to a flow through system. The multisensor approach will enable better measurement quality compared to the current ocean sensors. This, in turn, will potentially improve the current understanding of physical and biogeochemical processes from coastal to deep-sea environment. The pressure sensor element utilized a reinforced bulk micromachined diaphragm to achieve both higher sensitivity (27% higher, model data) and wider linear pressure operating range (> 400 psi, from combination of inner and outer bridge) compared to the conventional single diaphragm design. A temperature compensation bridge was incorporated on the sensor die to account for temperature drifts. A two-level packaging (wafer and system-level) scheme with protective coatings were developed to test the sensor in "simulated" ocean conditions. Finally, the reinforced diaphragm edge and the bossed structures were designed and fabricated using the masked-maskless etching process and their sensor performance were evaluated against the single diaphragm design. A nanowire-based Electrochemical detection-on-Chip (EoC) system was also developed to detect chemical/biological markers, especially nitrate fluxes. Different sensing modalities,involving a variety of nanosensor electrodes and different assembly techniques were investigated for suitability as electrochemical nitrate sensor. These architectures were also evaluated for robustness as a sensing platform. Enzyme-modified Au nanowires based electrochemical sensor showed excellent sensitivity (µM level) to biomarkers (cholesterol) in biological fluids (blood).These sensors, however, exhibited poor detection limits towards nitrate ions. Doped polypyrrole nanowire electrodes proved to be effective as nitrate sensors. A detection limit of 4.5±1 µM,sensitivity of 1.65 nAµM and stability of <15% variation from interfering ions were achieved on testing in a flow through environment. The nitrate sensor performance was at par with the current state of the art. Additionally, these sensors are batch fabricated (as arrays) reducing cost, require smaller sample volume, lesser space, power and are less prone to contamination problems.

A high temperature molten salt test loop that utilizes FLiNaK (LiF-NaF-KF) at 700ºC has been proposed by Oak Ridge National Laboratory (ORNL) to study molten salt flow characteristics through a pebble bed for applications in high temperature thermal systems, in particular the Pebble Bed – Advanced High Temperature Reactor (PB-AHTR). The University of Tennessee Nuclear Engineering Department has been tasked with developing and testing pressure instrumentation for direct measurements inside the high temperature environment. A nickel diaphragm based direct contact pressure sensor is developed for use in the salt. Capacitive and interferometric methods are used to infer the displacement of the diaphragm. Two sets of performance data were collected at high temperatures. The fiber optic, Fabry-Perot interferometric sensor was tested in a molten salt bath. The capacitive pressure sensor was tested at high temperatures in a furnace under argon cover gas.

Today’s MEMS technology allows manufacturing of miniaturized, low power sensors that sometimes exceeds the performance of conventional sensors. The pressure sensor market today is dominated by MEMS pressure sensors. In this thesis two different pressure sensor techniques are studied. The first concerns ways to improve the sensitivity in the most commonly occurring pressure sensor, namely such based on the piezoresistive technique. Since the giant piezoresistive effect was observed in silicon nanowires, it was assumed that a similar effect could be expected in nano-thin silicon films. However, it turned out that the conductivity was extremely sensitive to substrate bias and could therefore be controlled by varying the backside potential. Another important parameter was the resistivity time drift. Long time measurements showed a drastic variation in the resistance. Not even after several hours of measurement was steady state reached. The drift is explained by hole injection into the buried oxide as well as existence of mobile charges. The piezoresistive effect was studied and shown to be of the same magnitude as in bulk silicon. Later research has shown the existence of such an effect where the film thickness has to be less than around 20 nm.  The second area that has been studied is the pressure sensitivity of in acoustic resonators. Aluminium nitride thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes have been theoretically and experimentally studied in a comparative manner. The S0 Lamb mode is identified as the most pressure sensitive FPAR mode. The theoretical predictions were found to be in good agreement with the experiments. Additionally, the Lamb modes have been tested for their sensitivities to mass loading and their ability to operate in liquids, where the S0 mode showed good results. Finally, the pressure sensitivity in aluminium nitride thin film bulk wave resonators employing c- and tilted c-axis texture has been studied. The c-axis tilted FBAR demonstrates a substantially higher pressure sensitivity compared to its c-axis oriented counterpart.

Attitude and Heading angles are crucial parameters for navigation. Conventional navigation methods mostly uses IMU and GPS devices to calculate these angles. MEMS technology offers small sized, low cost IMU sensors with moderate performance. However, GPS cannot be used in underwater. Therefore, different aiding sensors are used in underwater vehicles in order to increase the accuracy. As the accuracy of devices increases, the cost of these devices also increases. In this thesis, rather than using GPS and high quality IMU sensors, low cost MEMS IMU sensor is used together with a magnetometer and a pressure sensor as aiding sensors. Considering the IMU error model and motion dynamics, two systems are designed and simulated using real data. The results seem to be satisfactory and using pressure sensor as an aiding sensor improves the attitude angles estimation.

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No description available.

Arbetet syftar till att skapa en prototyp av en textil trycksensor som kan känna av och skilja på olika typer av belastning. En lämplig metod för att på ett vetenskapligt sätt testa sagda prototyp har också utvecklats. Prototypen har tillverkats för hand på en datoriserad vävstol och de ingående materialen är piezoelektrisk poly(vinyldifluorid), PVDF, tvinnad tillsammans med ett konduktivt garn, Shieldex®, samt polyester. När PVDF-fiber utsätts för töjning genererar de en spänning, vars storlek står i relation till töjningen. Den vävda konstruktion som valdes till prototypen är en distansvara där väftinläggen lagts in i 7 olika lager för att skapa volym. Därmed möjliggörs en töjning av PVDF-fibern som relaterar till trycket strukturen utsätts för. För att utvärdera strukturen skapades tre likadana trycksensorer innehållandes fyra PVDF-fiber som lagts in med ett mellanrum på ca 1,5 cm. Dessa prototyper har sedan fästs på en egentillverkad ramp och PVDF- samt Shieldex®-garnet har kopplats in till ett oscilloskop. Därefter har vikter rullats över prototypen för att generera spänning, vilken har kunnat uppmätas med oscilloskopet. De uppmätta resultaten har analyserats och utvärderats med hjälp av Excel. Testerna visade tydligt att spänningen som uppmättes stod i relation till vikternas storlek; högre vikter gav en mätbart större spänning. Det finns dock stor varians bland resultaten och utvärdering av samtliga prover visar på stora standardavvikelser hos samtliga fiber. Detta innebär att även om det är tydligt att ökad vikt medför ökad signal så kan det finnas svårigheter i att avgöra storleken på vikten utifrån den uppmätta spänningen. / The aim of this project was to create a sensor in textile material which can register and recognize different kinds of pressure. A suitable method has been developed in order to scientifically investigate and evaluate the sensitivity of the prototypes. The prototypes have been produced with a computerized hand weave machine and the materials used were polyester and piezoelectric PVDF-fiber, twisted with a conductive yarn, Shieldex®. When a force is applied to the PVDF-fiber, causing an extension of the fiber, a voltage is generated directly related to the applied force. The final prototype is a woven textile with integrated monofilaments and weft inserted in seven different layers to create a voluminous structure. An extension by the PVDF-fiber is there by enabled to occur which is related to the force applied onto the structure. Three equable prototypes were produced, each consisting four separated PVDF-fibers which were inserted with a distance of 1, 5 cm from each other. The prototypes were further attached one by one on a homemade ramp and the PVDF- and Shieldex®-fibers were connected to an oscilloscope. Different weights were then rolled from the top of the ramp, generating a voltage each time it pressures a fiber, which were seen on the computer software of the oscilloscope. The results were afterwards analyzed and evaluated using Excel. A clear relationship between applied force and generated voltage is shown although there is a great variety among the test results on each weight along with large standard deviations. The exact weight generating a specific voltage is therefore difficult to determine.