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.

Current MEMS development is driven by the need to develop various 'Miniaturized Total Chemical Analysis Systems ([mu]TAS), biological and chemical sensing, drug delivery, molecular separation, microfiltration, amplification, and sequencing systems. In this work, the use of flexural plate wave devices as an actuator has been investigated.This research was done with the aim of developing a platform to build FPW devices for use in System-On-Chip applications. It is well known that acoustic forces generated by a flexural plate wave (FPW) device can cause fluid motion, by the principle of acoustic streaming. Also the proven ability of FPW devices to cause mixing, filtration and to work as a chemical-biological sensor can be used towards building a micromachined [mu]TAS. The effects of the IDT finger width, spacing, aperture, membrane thickness, and driving conditions on the device performance was studied to understand the impact of IDT design on device performance.

Electromechanical modeling efforts in the research field of vibration-based energy harvesting have been mostly focused on deterministic forms of vibrational input as in the typical case of harmonic excitation at resonance. However, ambient vibrational energy often has broader frequency content than a single harmonic, and in many cases it is entirely stochastic. As compared to the literature of harvesting deterministic forms of vibrational energy, few authors presented modeling approaches for energy harvesting from broadband random vibrations. These efforts have combined the input statistical information with the single-degree-of-freedom (SDOF) dynamics of the energy harvester to express the electromechanical response characteristics. In most cases, the vibrational input is assumed to have broadband frequency content, such as white noise. White noise has a flat power spectral density (PSD) that might in fact excite higher vibration modes of an electroelastic energy harvester. In particular, cantilevered piezoelectric energy harvesters constitute such continuous electroelastic systems with more than one vibration mode. The main component of this thesis presents analytical and numerical electroelastic modeling, simulations, and experimental validations of piezoelectric energy harvesting from broadband random excitation. The modeling approach employed herein is based on distributed-parameter electroelastic formulation to ensure that the effects of higher vibration modes are included. The goal is to predict the expected value of the power output and the mean-square shunted vibration response in terms of the given PSD or time history of the random vibrational input. The analytical method is based on the PSD of random base excitation and distributed-parameter frequency response functions of the coupled voltage output and shunted vibration response. The first one of the two numerical solution methods employs the Fourier series representation of the base acceleration history in a Runge-Kutta-based ordinary differential equation solver while the second method uses an Euler-Maruyama scheme to directly solve the resulting electroelastic stochastic differential equations. The analytical and numerical simulations are compared with several experiments for a brass-reinforced PZT-5H cantilever bimorph under different random excitation levels.In addition to base-excited cantilevered configurations, energy harvesting using prismatic piezoelectric stack configurations is investigated. Electromechanical modeling and numerical simulations are given and validated through experiments for a multi-layer PZT-5H stack. After validating the electromechanical models for specific experimentally configurations and samples, various piezoelectric materials are compared theoretically for energy harvesting from random vibrations. Finally, energy harvesting from narrowband random vibrationsusing both configurations are investigated theoretically and experimentally.

In this work we have investigated the electronic properties of several types of molecular systems involving a metallic element. Our motivation for such applications on metallic compounds was to obtain an accurate description of close lying electronic states, in which the relativistic effects of heavy atoms are known to be important. Thus various approaches and methods have been employed to treat these effects, including the multi-configurational method, with atomic pseudopotentials and large basis sets. In the first study, we have determined the properties of the low lying electronic states of the diatomic compounds MX, whose combinations in the solid phase produce ionic semi-conductor materials with piezoelectric properties. Based on highly correlated ab initio calculations, we have elucidated the common properties of the low lying electronic states of these diatomic compounds with eight valence electrons, which can be considered as precursors for piezoelectric effects in their solid phase. Based on our electronic structure calculations, we could identify among these diatomic compounds those who could lead to good candidates for piezoelectric effects. As the second application, we have determined the electronic structure and the spectroscopic constants for the ground state of the HZnF molecule and for the low lying electronic states of its diatomic fragments. This application was initiated and motivated by interesting and puzzling results on the close system HZnCl. Comforted by our experience with the previous studies, we used the pseudopotentials approach to obtain an accurate description of the low lying states of ZnH which could be satisfactorily compared with existing data. Next, the ZnF and ZnCl diatomic molecules have been studied with the same ansatz to reveal the properties of so far unknown electronic states. Finally, the potential energy surface of the ground state of HZnF has been determined, and several spectroscopic properties have been deduced

No description available.

The electric potential changes under uniaxial loading in some minerals and rocks have long been recognized. To daylight the electrical response of some minerals and rocks against applied stress, both theoretical studies and laboratory experiments are conducted. Some theories are also proposed by different researchers, in order to explain the electric potential variations. However, the mechanisms leading to electrical potential generation have not been fully explained yet. In the explanation of electric potential changes observed in rocks, type of the observed rock and the rock forming minerals in the rock fabric play an important role. One theory is based on the fundamentals of piezoelectricity only. However the relation between the stress state and the electric generation is not fully understood. This thesis aims to make a further contribution to the studies on understanding the electric potential change in rocks, containing quartz, which is a common piezoelectric mineral, under uniaxial loading conditions. Three types of rocks, namely quartz-sandstone, granite and granodiorite, are tested, and the stress and electric potential (EP) variations are recorded during the uniaxial loading experiments in a continuous manner. The experiments are conducted at three different loading rates, in order to investigate the effect of loading rate on the electrification mechanism. Also step loading experiments are conducted. Results indicated that, application of uniaxial stress creates a clear change in the EP responses of three quartz bearing rock types. The possible relationships between the EP generation and the level of applied stress are investigated based on the initial and final potential values (EPinitial, EPfinal), the potential just before the time of failure (EPUCS), the spike-like potential jump at the time of failure (&amp / #8710 / V), which are derived from the recorded data of the experiments.

Nanotechnology and nanoscience are experiencing rapid development in the last decade. Intensive research has been carried out on nanostructures synthesis and nanodevices fabrication. Due to its small size, a nanodevice usually requires an extremely small power to operate. However, to make the novel nanodevice work, an external power source is normally needed, which can either be a battery or a power source, thus, the size of the battery is usually much larger than that of the device and its life time is limited. It is highly desired to have a nanoscale size power source that harvests its energy from the environment so that it works independently and wirelessly to provide power to the nanodevices. This dissertation provides a solid solution to this dilemma based on nanotechnology. Starting from the synthesis of well aligned ZnO nanowire arrays on different substrates, an innovative method is presented first to measure the mechanical property of the as-synthesized ZnO nanowire arrays by using AFM without destroying and manipulating the sample. This technique is then extended to converte mechanical energy into electricity by scanning the nanowire arrays using a AFM tip in contact mode. Due to the unique semiconducting and piezoelectric dual properties of ZnO, mechanical energy is converted into electricity and is effectively output. This is the invention of the piezoelectric nanogenerator. Then, by replacing AFM tips using a zigzag top electrode, the first prototype direct-cirrent nanogenerator driven by ultrasonic wave has been fabricated. Further investigations have also been carried out about the effect of ZnO carrier density on the output power, and the power generating property of oligomer functionalized ZnO nanowires. This desertation established the fundamental mechanism for the nanogenerator, and it provides a new path towards self-powered nanosystems, which has key applications in in-vivo biosensing, MEMS, environmental mornitoring, defence technology and even personal electronics.

Thesis (PhD)--Macquarie University, School of Mathematics, Physics, Computing and Electronics, 1999. / "1998"--T.p. Includes bibliographical references.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / Thesis presented in partial fulfilment of the requirements for the degree Master of Science in Engineering at the University of Stellenbosch / ENGLISH ABSTRACT: Measurement of pressure with zinc oxide (ZnO) nanowires was investigated. ZnO exhibits the piezoelectric effect, generating a voltage when pressure is applied to the material. This relationship between pressure and output voltage was used to make a pressure sensor. A study of the physical and mathematical working of the piezoelectric effect in ZnO nanowires was done. Simulations were conducted by means of specialised software to test the theory. The simulations gave results as the theory had predicted. ZnO nanowires were grown using various methods. Vapour liquid solid (VLS) was found to be the best method to grow uniform and dense arrays of ZnO nanowires. Statistical methods were employed to obtain the optimal parameters for the growth of ZnO nanowires through the VLS method. After the growth of the ZnO nanowires a pressure sensor was built. The manufacturing of the pressure sensor consisted of different steps. The sensors were tested to verify that they worked as described in theory and as shown in the simulations. The output voltage was lower than the simulated value due to imperfections and losses throughout the system. The output voltage versus applied pressure graphs did coincide with the bulk ZnO materials as well as related products, such as force sensing resistors. The output voltage is too low, but there are various methods by which the output voltage can be increased. These methods are discussed. The finished sensor can be used to continuously monitor pressure on a plane. / AFRIKAANSE OPSOMMING: Die meting van druk deur sink oksied (ZnO) nanodrade was ondersoek. ZnO toon die piëzo-elektriese effek - spanning word gegenereer wanneer druk op die materiaal aangewend word. Hierdie verhouding tussen druk en uitsetspanning is gebruik om ’n druksensor te vervaardig. ’n Studie van die fisiese en wiskundige werking van die piëzo-elektriese effek in ZnO nanodrade is gedoen. Simulasies deur middel van gespesialiseerde sagteware is uitgevoer om die teorie te bevestig. Die simulasies het resultate getoon soos deur die teorie beskryf word. ZnO nanodrade is gegroei deur verskillende metodes. Verdamping vloeistof vastestof (VVV) is as die beste metode gevind om uniforme en digte skikkings van ZnO nanodrade te kry. Statistiese metodes is aangewend om die optimale parameters vir die groei van ZnO nanodrade deur middel van die VVV metode te kry. Na afloop van die groei van die ZnO nanodrade is ’n druksensor vervaardig. Die vervaardigingsproses het uit verskillende stappe bestaan, ten einde die bou van ’n werkende druksensor uit die ZnO nanodrade te realiseer. Die sensors is getoets om te bevestig dat dit werk, soos beskryf deur die teorie en gewys in die simulasies. Die uitsetspanning was laer as wat verwag was as gevolg van onvolmaakthede en verliese in die hele stelsel. Die uitsetspanning teenoor druk grafieke van die sensor het ooreengestem met die van die grootmaat materiale, asook verwante produkte soos druk sensitiewe weerstande. Die uitset spanning is baie laag en daar bestaan verskillende maniere waarop die uitsetspanning verhoog kan word. Hierdie metodes word bespreek.

Les microsystèmes électromécaniques (MEMS) ont été développés dès le début des années 1980 en s'appuyant sur la technologie de l'industrie microélectronique. Ils ont d'abord été utilisés dans les accéléromètres et les airbags des automobiles. Depuis lors ils se diversifient et connaissent un important essor, notamment grâce à la rapidité De la réponse des matériaux piézoélectriques. La technologie des couches minces piézoélectriques a permis la miniaturisation et les déformations sous tensions d'actionnement plus faibles. Parmi les matériaux piézoélectriques, les films minces de PbZrTiO3 (PZT) morphotropique sont fréquemment utilisés pour leurs propriétés électromécaniques remarquables. Le PZT fabriqué par la voie sol-gel au CEA Leti est à l'état de l'art mondial. Dans le souci de continuer à être compétitif, plusieurs stratégies de R&D sont envisagées, notamment des études approfondies de la microstructure des films PZT pour l'optimiser, afin d'atteindre les propriétés ultimes du PZT. Dans ce but, cette thèse recherche les corrélations entre la microstructure et l'effet piézoélectrique du PZT. Le PZT morphotropique massif, apparu dans les années 1950, est un matériau bien étudié du point de vue microstructurale et piézoélectrique. Il existe plusieurs théories expliquant ses performances piézoélectriques au niveau microscopique. Pour citer les plus connues, le basculement de domaine des phases tétragonale et rhomboédrique, le réarrangement des nano-domaines rhomboédriques, la rotation de l'axe de polarisation dans la phase monoclinique et la transition de phase. Les films minces de PZT morphotropique sont apparus dans les années 1990. Leur microstructure diffère radicalement du PZT massif. Le PZT sol-gel étudié dans ce manuscrit, est contraint et possède une orientation préférentielle des cristaux, des domaines nanométriques et un gradient chimique de Zr et Ti dans l'épaisseur. Notre but est d'étudier les liens entre la microstructure complexe de ces films et leurs propriétés piézoélectriques en utilisant la caractérisation par diffraction des rayons X (DRX). Grace à l'accès au nano-faisceau à l'ESRF, nous avons pu étudier l'influence du gradient chimique de Zr/Ti sur la microstructure de PZT. Les résultats ont montré que la variation de concentration de Zr et Ti engendre une variation du rapport des phases tétragonale et rhomboédrique dans l'épaisseur de la couche. Cette variation suit les oscillations de Zr/Ti dans les films observées par SIMS. Cette observation montre la sensibilité de la microstructure sur la composition chimique. De même, il en résulte la possibilité d'améliorer l'homogénéité de composition du PZT et de ses performances. Car plus le PZT est homogène en composition, meilleurs sont ses coefficients piézoélectriques (d33, e31). Par la suite nous avons effectués des expériences in-situ sous champ électrique sur des capacités contenant le PZT avec le gradient de composition atténué. La microstructure de PZT a été affinée en utilisant la phase tétragonale et rhomboédrique. A 0V, on estime que le PZT contient 40% de phase rhomboédrique et 60% de phase tétragonale. A 30V, on n'observe plus que la présence de la phase rhomboédrique. Les résultats montrent une diminution de la proportion de phase tétragonale au profit de la phase rhomboédrique sous champ électrique. Pour finir nous avons étudié l'influence du gradient de concentration sur l'amplitude du changement de phase en analysant deux échantillons de gradient Zr/Ti différents par DRX in-situ. Nous avons pu montrer que plus l'échantillon est homogène chimiquement, plus il est sujet à la transition de phase sous champ électrique et plus il est performant piézoélectriquement. Finalement, afin d'améliorer les performances piézoélectriques des films PZT, nous proposons de fabriquer des films plus homogènes et plus riches en Ti pour amplifier la transition de phase dans les films. / MEMS have been developed since 1980, when they appeared as derivatives from the microelectronic industry. They were first used in accelerometers and car airbags. They have diversified since then and expanded. One of the main contributors to this expansion are piezoelectric materials. Among them, PbZrTiO3 (PZT) is widely used for its outstanding piezoelectric performances. Sol-gel PZT thin films fabricated at CEA are worldwide state of the art. In order to stay competitive, several R&D strategies have been developed. One of them is a detailed study of PZT microstructure in order to draw correlations with the piezoelectric effect in PZT films. The goal of this study is to optimize PZT microstructure aiming to reach its best piezoelectric properties. For this purpose, this thesis takes advantage of numerous studies performed on PZT bulk ceramics in order to analyze PZT thin films microstructure and its modifications with voltage. PZT bulk ceramics of morphotropic composition are now well known from the piezoelectric and microstructural point of view. There are several theories explaining the piezoelectric effect at the microscopic level, namely tetragonal and rhombohedral domain switching, rhombohedral nanodomains rearrangement, polarization axis rotation in the monoclinic phase and the phase transition.Morphotropic PZT thin films have emerged more recently. Their microstructure is very different from the bulk PZT. Indeed, sol-gel PZT films studied in this manuscript are stressed and contain preferred oriented nanoscale crystals and Ti/Zr composition gradient through the film thickness. Our goal is to study links between the complex microstructure of these films and their piezoelectric properties using X-ray diffraction (XRD).Thanks to the nano-beam at ESRF, we were able to study the influence of the Zr/Ti chemical gradient on the PZT microstructure. Our observations showed that the composition gradient gives rise to a variation of the tetragonal and rhombohedral phase ratio in the layer thickness. This variation follows Zr/Ti composition oscillations evidenced by SIMS. This experiment shows the sensitivity of PZT microstructure to the PZT chemical composition. At the same time, it suggests the possibility of improving the composition homogeneity of PZT and its performances. The more the PZT composition is homogeneous, the better the piezoelectric coefficients are.Then, we performed in-situ XRD under electric field experiments on a capacitor containing the PZT active layer with an attenuated Zr/Ti gradient. The PZT diffraction pattern was refined using the tetragonal and the rhombohedral PZT phases. At 0V PZT contains 40% of rhombohedral phase and 60% of tetragonal phase. At 30V, no tetragonal phase is observed any more. Results show an electric field induced phase transition from the tetragonal to the rhombohedral phase.Finally, we used in-situ XRD to study the influence of Zr/Ti composition gradient on the amplitude of the phase transition of two PZT samples with different Zr/Ti gradient. We showed that the more the sample is homogeneous in composition, the more phase transition it exhibits and the more it is performant.Finally, to improve the piezoelectric performances of PZT films, we propose to improve PZT compositional homogeneity and slightly increase the Ti content to promote the tetragonal phase in order to amplify the phase transition under voltage.