Dissertations / Theses on the topic 'FLEXIBLE PIEZOELECTRIC'

Structural health monitoring is an emerging technology addressing major concerns in the operation of in-service structures, i.e. the reliability of the structures and the cost associated with maintaining reliability. In this thesis, the motivation of structural health monitoring has been discussed within the framework of non-destructive evaluation. To be a common failure mode, connection damage or lap joint damage is chosen as damage signature in a structure, consisting of a flexible aluminum beam jointed on a frame by bolts. To simulate connection damage, the stress relaxing on the bolt is achieved by the action of bolt looseness quantified by rotation angle. The dynamic response of flexible beam system is monitored with a piezoelectric transducer. To produce exciting signal, an electro-mechanical system processes the voltage signal. Response interpretation is carried out on PC or on an embedded DSP chip in real time. The two analysis methods, frequency response method and wavelet analysis method, were explored to identify early "changes" of beam connection so as to reach the goal of structural health monitoring.

The capacity of humankind to mimic fish-like locomotion for engineering applications depends mainly on the availability of suitable actuators. Researchers have recently focused on developing robotic fish using smart materials, particularly Ionic Polymer-Metal Composites (IPMCs), as a compliant, noise-free, and scalable alternative to conventional motor-based propulsion systems. In this thesis, we investigate fish-like self propulsion using flexible bimorphs made of Macro-Fiber Composite (MFC) piezoelectric laminates. Similar to IPMCs, MFCs also exhibit high efficiency in size, energy consumption, and noise reduction. In addition, MFCs offer large dynamic forces in bending actuation, strong electromechanical coupling as well as both low-frequency and high-frequency performance capabilities. The experimental component of the presented work focuses on the characterization of an MFC bimorph propulsor for thrust generation in a quiescent fluid as well as the development of a preliminary robotic fish prototype incorporating a microcontroller and a printed-circuit-board (PCB) amplifier to generate high actuation voltage for battery-powered free locomotion. From the theoretical standpoint, a reliable modeling framework that couples the actuator dynamics, hydroelasticity, and fish locomotion theory is essential to both design and control of robotic fish. Therefore, a distributed-parameter electroelastic model with fluid effects and actuator dynamics is coupled with the elongated body theory. Both in-air and underwater experiments are performed to verify the incorporation of hydrodynamic effects in the linear actuation regime. For electroelastically nonlinear actuation levels, experimentally obtained underwater vibration response is coupled with the elongated body theory to predict the thrust output. Experiments are conducted to validate the electrohydroelastic modeling approach employed in this work and to characterize the performance of an MFC bimorph propulsor. Finally, a wireless battery-powered preliminary robotic fish prototype is developed and tested in free locomotion at different frequency and voltage levels.

Actuator placement is a major concern in control system designs. Utilizing piezoelectric actuators increases the complexity of actuator designs, because both actuator location and dimensions need to be considered. A comprehensive study was conducted in this dissertation on the optimization of piezoelectric actuator designs for vibration suppression of flexible structures. The investigation on the optimal piezoelectric actuator designs were grouped into two parts. Part one covered actuator designs when the same number of actuators as the controlled modes are used. Approaches were formed to optimally design piezoelectric actuators which requires least control efforts. In part two of this dissertation, a method named the Weighted Pseudoinverse Method was introduced to deal with the cases in which fewer actuators than the controlled modes are utilized. The weighted pseudoinverse method yields a optimal transformation from modal control forces into the actuator-moments in physical space. Based on the Weighted pseudoinverse method, the piezoelectric actuator designs were optimized to ensure least-control-effort actuator designs. A simply-supported beam was used as an example to demonstrate the effectiveness of the design methods proposed in this dissertation. However, the design methods are applicable to general cases.
Ph. D.

Integrated (IUTs) and flexible ultrasonic transducers (FUTs) have been found to be of great interest for structural health monitoring (SHM) of graphite/epoxy (Gr/Ep) composite parts and structures. Because certain Gr/Ep composites do not have sufficient electrical conductivity, bottom electrodes are required for the IUT fabrication. Also FUTs using insulating polyimide (PI) membrane which offers high flexibility, bottom electrode is required as well. One main objective is to develop the electroless plating technique to deposit nickel (Ni) or silver (Ag) onto Gr/Ep composites and PI for IUT or FUT fabrication. The pre-treatments (cleaning, etching, sensibilization, activation and reduction) and reaction conditions (bath chemistry, temperature, time, agitation, etc.) have been investigated. Recipes of electroless nickel (EN) plating at room temperature (RT) and 90°C and RT electroless Ag plating have been developed. The interfacial adhesion of the Ni or Ag/substrate was also tested. The conductivity of the fabricated bottom electrodes was tested by ohmmeter. A 50~60µm piezoelectric film was fabricated by sol-gel spray technique. IUTs and FUTs consisting of these EN bottom electrodes, piezoelectric film and Ag paste top electrode perform well for SHM purposes.
Les capteurs ultrasonores flexible (CUF) et intégré (CUI) sont très intéressants pour le suivi de la santé structurelle (SSS) des pièces de structures et de composites, composées à partir de carbone/époxyde (C/Ep). Parce que le C/Ep n'a pas suffisamment de conductivité électrique, une électrode de base est nécessaire pour la fabrication de CUIs. De plus, pour le CUF utilisant du polyimide (PI) comme membrane isolante nécessite aussi l'utilisation d'une électrode de base. Un des principaux objectifs de ce mémoire est de remédier à ce problème par le développement d'une technique de placage au tampon. Cette dernière déposera du nickel (Ni) ou de l'argent (Ag) sur le C/Ep et le PI pour obtenir des CUIs ou des CUFs. Les prétraitements (nettoyage, attaque chimique, sensibilisation, activation et réduction) et les conditions de réaction (bain chimique, température, temps, agitation, etc.) ont été étudiés. Les procédures pour le placage au tampon du nickel (PTN) à la température de la pièce (TP) et à 90C ainsi que pour l'Ag à TP furent développées. Les adhésions de surface du Ni ou de l'Ag avec le substrat furent testées. Les conductivités électriques des électrodes de base furent testées avec un ohmmètre. Un film piézo-électrique de 50~60 μm fut fabriqué par une technique sol-gel. Les CUI et CUF fabriqués avec l'électrode de base faite à partir du PTN, du film piézo-électrique et une pâte d'Ag comme électrode de surface, excelle bien pour les besoins en SSS.

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This thesis details the experimental analysis of an active damping control technique applied to the Naval Postgraduate School's Flexible Spacecraft Simulator using piezoceramic sensors and actuators. The mass property of the flexible arm is varied to study the frequency effects on the Positive Position Feedback (PPF) algorithm. Multi-modal dynamics response is analytically studied using a finite-element model of a cantilevered beam while under the influence of three different control laws: a basic law derived rom the Lyapunov Stability Theorem, PPF and Strain Rate Feedback (SRF). The advantages and disadvantages of using PPF and SRF for active damping control are discussed.

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: Actuator placement algorithm; piezoelectric actuators; LQR; Galerkin; supervisory control; active vibration control; FEA; switching policy; dSPACE. Includes bibliographical references (p. 58-64).

Health monitoring of aeronautic structures and human beings is becoming crucial because of the human safety issues. In this thesis integrated (IUTs) and flexible ultrasonic transducers (FUTs) have been developed using a sol-gel spray piezoelectric film fabrication technology. IUTs can be fabricated directly onto the structures with curved surfaces even on-site. FUTs were made using membrane substrates of thickness less than 75 mum. In-situ monitoring of AI airframe thickness was carried out and the thickness measurement accuracy was better than 36 mum and 41 mum for IUT and FUT, respectively. The thickness of the ice on top of the AI airframe was also measured. Two crucial piezoelectric constants d33 and d31 of the composite film were measured with laser interferometer and optical coherence tomography system, respectively. Pulse and breath of a human being were also monitored using flexible piezoelectric membrane sensors. In addition, bones in human body were observed using FUTs as well and their performance is comparable to that of commercial ultrasonic transducers.

Thesis (M.S. in Systems Technology (Space Systems Operations)) Naval Postgraduate School, September 1993.
Thesis advisor(s): Brij N. Agrawal. "September 1993." Includes bibliographical references. Also available online.

Flexible foams have unique properties that make them well-suited to several engineering systems. They are often used in impact-related applications because of their superior energy absorption performance. Many multifunctional materials are also derived from flexible foams due to their high customizability, which allows them to satisfy a wide range of performance requirements. Though flexible foams have high potential in these and other classes of material applications, their success relies on the proper characterization of their complex behavior. This thesis promotes the application of flexible foams by characterizing their electromechanical response through both experimental and theoretical approaches. One study in this thesis theoretically determines material indices that minimize a foam's mass and cost while meeting particular energy absorption requirements. These novel indices are combined with a common Ashby approach to facilitate materials selection of energy-absorbing foam components. Another study uses a particular multifunctional nanocomposite foam to experimentally determine deviations in its voltage response while under a cyclic impacting regime; specifically, factors of transient effects, environmental conditions (humidity and temperature), and permanent material degradation are investigated. Results presented in this thesis promote the application of flexible foams to various forms of impact-absorbing sports equipment (specifically football helmet pads and gait-sensing shoe insoles), but are also useful in various other engineering designs.

In real operating environments, flexible structures exhibiting dynamic oscillations such as aircraft and spacecraft can experience large changes in temperature during their normal operating cycle, typically in the range -70 to 80 degrees Celsius. The use of piezoelectric actuators and sensors to control these dynamic oscillations have been widely explored at constant temperature, although only limited studies have been conducted on the effect that varying temperature has on the active control of flexible structures. The objective of this research is to study the influence of PZT sensors and actuators for vibration control of flexible structures where nonlinearities in piezoelectric and structural material properties change as the system temperatures vary significantly with time. This involved the development of a set of data based parameters that enabled the accurate modelling of a nonlinear flexible system in which its dynamics are actively controlled via the use of piezoelectric sensors and actuators. These parameters determined the design of a control scheme to actively control the system over a large range of operating temperatures, and give an optimised control performance throughout its operating regime. The work reported in this thesis describes selected methods for rapidly examining a number of the more common nonlinear properties of PZT associated with vibration control. An extensive numerical and experimental investigation is performed which shows that when used in active vibration control applications, the variations in PZT properties with temperature can ultimately affect the ability of the piezoelectric actuator and sensors to suppress vibration in flexible structures. Accurate simulation models of the lightweight piezo-actuated cantilevered structures were developed to evaluate the performance of a number of common vibration control schemes subject to significant temperature variations. This research was then extended to an innovative scaled wing-type structure subjected to temperature variations. A suitable adaptive self-tuning control scheme was developed and investigated numerically and experimentally, illustrating the benefit of adaptive control in this instance. The adaptive control technique was shown numerically and experimentally to provide improved settling times and damping ratios over equivalent fixed gain controllers for the class of structures investigated where limited control authority exists. The experimental investigation of PZT sensors and actuators has provided further understanding of the nonlinear behaviour of various light, flexible structures where temperature effects on the system dynamics and control are significant. This research has unveiled previously unreported nonlinearities and has expanded on traditional nonlinearities. These results can assist with the detailed design of applications involving PZT sensors and actuators in for example the aerospace and automotive industries.

Les actionneurs multi-axes sont de plus en plus prisés par les concepteurs de systèmes de nanopositionnement car ils permettent une réduction de l'espace occupé et de l'énergie consommée, une dextérité plus grande et une modularité avec peu de contraintes pour les applications. Certains de ces actionneurs et systèmes multi-axes sont cependant caractérisés par des oscillations mal-amorties qui compromettent de manière drastique leurs performances générales. Cette thèse concerne l'exploitation des techniques de commande en boucle-ouverte input-shaping classiquement utilisées pour amortir de manière sans capteurs les oscillations dans les systèmes mono-axes et les étendent pour qu'ils soient utilisables pour les systèmes multi-axes. Les résultats proposés dans la thèse qui sont des techniques input-shaping multivariables sont ensuite appliquées sur des actionneurs piézoélectriques classiquement dédiés pour les applications de nanopositionnement
Multi-axes actuators are becoming more and more tempting to nanopositioning system designers as they enable them to save space, reduce energy consumption, increase dexterity and offer more modularity and freedom with fewer constraints to their applications. Some of these multi-axes actuators and systems exhibit however badly damped vibrations which strongly compromise their global performances. This thesis work exploits the advantages of the well-known feedforward input shaping techniques usually used to damp vibrations in monovariable (SISO) systems to present a new multivariable (MIMO) input shaping technique that can be used to damp vibrations in multi-axes systems. The approach that was used in this study is to extend a previous work that was done on multiple-input single-output (MISO) systems and generalize it for MIMO systems. The study demonstrates also the application of this newly developed technique on different piezoelectric actuators commonly used in nanopositioning systems

The development of micro systems with smart sensing capabilities is paving the way to progresses in the technology for humanoid robotics. The importance of sensory feedback has been recognized the enabler of a high degree of autonomy for robotic systems. In tactile applications, it can be exploited not only to avoid objects slipping during their manipulation but also to allow safe interaction with humans and unknown objects and environments. In order to ensure the minimal deformation of an object during subtle manipulation tasks, information not only on contact forces between the object and fingers but also on contact geometry and contact friction characteristics has to be provided. Touch, unlike other senses, is a critical component that plays a fundamental role in dexterous manipulation capabilities and in the evaluation of objects properties such as type of material, shape, texture, stiffness, which is not easily possible by vision alone. Understanding of unstructured environments is made possible by touch through the determination of stress distribution in the surrounding area of physical contact. To this aim, tactile sensing and pressure detection systems should be integrated as an artificial tactile system. As illustrated in the Chapter I, the role of external stimuli detection in humans is provided by a great number of sensorial receptors: they are specialized endings whose structure and location in the skin determine their specific signal transmission characteristics. Especially, mechanoreceptors are specialized in the conversion of the mechanical deformations caused by force, vibration or slip on skin into electrical nerve impulses which are processed and encoded by the central nervous system. Highly miniaturized systems based on MEMS technology seem to imitate properly the large number of fast responsive mechanoreceptors present in human skin. Moreover, an artificial electronic skin should be lightweight, flexible, soft and wearable and it should be fabricated with compliant materials. In this respect a big challenge of bio-inspired technologies is the efficient application of flexible active materials to convert the mechanical pressure or stress into a usable electric signal (voltage or current). In the emerging field of soft active materials, able of large deformation, piezoelectrics have been recognized as a really promising and attractive material in both sensing and actuation applications. As outlined in Chapter II, there is a wide choice of materials and material forms (ceramics: PZT; polycrystalline films: ZnO, AlN; polymers and copolymers: PVDF, PVDF-TrFe) which are actively piezoelectric and exhibit features more or less attractive. Among them, aluminum nitride is a promising piezoelectric material for flexible technology. It has moderate piezoelectric coefficient, when available in c-axis oriented polycrystalline columnar structure, but, at same time, it exhibits low dielectric constant, high temperature stability, large band gap, large electrical resistivity, high breakdown voltage and low dielectric loss which make it suitable for transducers and high thermal conductivity which implies low thermal drifts. The high chemical stability allows AlN to be used in humid environments. Moreover, all the above properties and its deposition method make AlN compatible with CMOS technology. Exploiting the features of the AlN, three-dimensional AlN dome-shaped cells, embedded between two metal electrodes, are proposed in this thesis. They are fabricated on general purpose Kapton™ substrate, exploiting the flexibility of the polymer and the electrical stability of the semiconductor at the same time. As matter of fact, the crystalline layers release a compressive stress over the polymer, generating three-dimensional structures with reduced stiffness, compared to the semiconductor materials. In Chapter III, a mathematical model to calculate the residual stresses which arise because of mismatch in coefficient of thermal expansion between layers and because of mismatch in lattice constants between the substrate and the epitaxially grown films is adopted. The theoretical equation is then used to evaluate the dependence of geometrical features of the fabricated three-dimensional structures on compressive residual stress. Moreover, FEM simulations and theoretical models analysis are developed in order to qualitative explore the operation principle of curved membranes, which are labelled dome-shaped diaphragm transducers (DSDT), both as sensors and as piezo-actuators and for the related design optimization. For the reliability of the proposed device as a force/pressure sensor and piezo-actuator, an exhaustive electromechanical characterization of the devices is carried out. A complete description of the microfabrication processes is also provided. As shown in Chapter IV, standard microfabrication techniques are employed to fabricate the array of DSDTs. The overall microfabrication process involves deposition of metal and piezoelectric films, photolithography and plasma-based dry and wet etching to pattern thin films with the desired features. The DSDT devices are designed and developed according to FEM and theoretical analysis and following the typical requirements of force/pressure systems for tactile applications. Experimental analyses are also accomplished to extract the relationship between the compressive residual stress due to the aluminum nitride and the geometries of the devices. They reveal different deformations, proving the dependence of the geometrical features of the three-dimensional structures on residual stress. Moreover, electrical characterization is performed to determine capacitance and impedance of the DSDTs and to experimentally calculate the relative dielectric constant of sputtered AlN piezoelectric film. In order to investigate the mechanical behaviour of the curved circular transducers, a characterization of the flexural deflection modes of the DSDT membranes is carried out. The natural frequency of vibrations and the corresponding displacements are measured by a Laser Doppler Vibrometer when a suitable oscillating voltage, with known amplitude, is applied to drive the piezo-DSDTs. Finally, being developed for tactile sensing purpose, the proposed technology is tested in order to explore the electromechanical response of the device when impulsive dynamic and/or long static forces are applied. The study on the impulsive dynamic and long static stimuli detection is then performed by using an ad hoc setup measuring both the applied loading forces and the corresponding generated voltage and capacitance variation. These measurements allow a thorough test of the sensing abilities of the AlN-based DSDT cells. Finally, as stated in Chapter V, the proposed technology exhibits an improved electromechanical coupling with higher mechanical deformation per unit energy compared with the conventional plate structures, when the devices are used as piezo-actuator. On the other hand, it is well suited to realize large area tactile sensors for robotics applications, opening up new perspectives to the development of latest generation biomimetic sensors and allowing the design and the fabrication of miniaturized devices.

This paper considers the control of externally symmetric vector second order systems using an analytical upper bound method. The structural model is a cantilevered aluminum beam with a collocated pair of piezoceramic patches to serve as actuators and sensors. A computationally efficient method for approximating the H-infinity norm for externally symmetric systems is presented. The approximation method is then used to calculate a scalar output feedback controller to guarantee a closed-loop norm less than any user defined value. This method is tested with a finite-element representation of the beam, and then verified experimentally.

Abstract In this thesis flexible electronics composite materials were developed and utilized in pressure sensors. Additionally, stretchable materials based on piezoresistive structures were fabricated and their feasibility for printed electronics switches and stretchable strain sensors was investigated. In the first part of the thesis two types of composite materials were developed based on polyurethane foam with added carbon powder and on liquid crystal polymer with ceramic powder. The first developed composite was utilized in piezoresistive and capacitive hybrid sensors and the latter one for an additive manufactured piezoelectric sensor strip suitable for operation at elevated temperatures. The formable hybrid sensor achieved a maximum pressure sensitivity of 0.338 kPa-1 with response and recovery times less than 200 ms at pressures over 200 kPa and also showed a linear response. The sensor could be utilized, for example, in wearable electronics and robotics. The new type of piezoelectric material showed piezoelectric coefficients of d33 > 14 pC/N and g33 > 108 mVm/N at pressure below 10 kPa with a wide pressure sensing range up to 4.5 MPa. This was higher than that previously achieved for materials fabricated using traditional printing techniques. The piezoelectric sensor would be suitable for industrial process control at elevated temperatures. In the second part of the thesis the stretchable materials were utilized in a new type of piezoresistive structure to fabricate one of the first stretchable switches and a machine washable self-adherable strain sensor. The developed stretchable switch could be actuated with either stretching or vibration with a minimum movement of < 2 μm. The versatile strain sensor with a tunable resistance-strain characteristic achieved the currently highest reported gauge factor (>105) at > 70% stretching. The strain sensor could be utilized for sensing human body movements and physiological signals
Tiivistelmä Väitöstyössä kehitettiin joustavan elektroniikan komposiittimateriaaleja, joita hyödynnettiin paineantureissa sekä käytettiin venytettäviä materiaaleja painettavan elektroniikan kytkimen ja venymäanturin valmistukseen. Työn ensimmäisessä osassa kehitettiin kahdenlaisia komposiittimateriaaleja, joista ensimmäinen pohjautui polyuretaanivaahtoihin, joihin sisällytettiin hiilijauhetta, sekä toinen nestekidepolymeeriin, johon lisättiin keraamijauhetta. Ensimmäistä kehitettyä komposiittia hyödynnettiin pietsoresistiivisessä ja -kapasitiivisessa hybridianturissa ja jälkimmäistä lisäaine valmistettavassa pietsosähköisessä anturinauhassa, joka soveltui kohotettuihin lämpötiloihin. Muovattavalla hybridianturilla saavutettiin herkkyyden maksimiarvoksi 0.338 kPa-1, alle 200 ms vaste- ja palautumisajat yli 200 kPa paineessa ja lineaarinen vaste. Anturia voitaisiin monipuolisesti hyödyntää mm. puettavassa elektroniikassa ja robotiikassa. Uudenlaisella pietsosähköisellä materiaalilla saavutettiin pietsosähköiset kertoimet (d33 > 14 pC/N ja g33 > 108 mVm/N < 10 kPa paineessa), jotka olivat korkeammat kuin perinteisin tulostusmenetelmin valmistetuilla materiaaleilla. Pietsosähköinen anturi soveltuisi mm. teolliseen prosessivalvontaan kohotetuissa lämpötiloissa. Toisessa osassa hyödynnettiin venytettäviä materiaaleja uudentyyppisissä pietsoresistiivisissä rakenteissa ensimmäisten venytettävän painettavan elektroniikan kytkimen sekä konepestävän itsekiinnityttävän venymäanturin valmistamiseksi. Tulokset on esitetty kahdessa julkaisussa, joista ensimmäinen keskittyi kytkimen valmistamiseen ja toimintaan sekä toinen venymäanturin toimintaan ihmiskehon liikkeen ja signaalien mittaamiseksi. Kehitettyä kytkintä voitiin aktuoida monipuolisesti esim. venytyksen tai värinän avulla alle 2 μm liikkeellä. Monipuolisella venymäanturilla saavutettiin säädettävä resistanssi-venymä suhde korkeimmalla tähän asti ilmoitettu herkkyydellä (>105) yli 70% venytyksellä. Venymäanturia voitiin hyödyntää ihmiskehon liikkeiden ja fysiologisten signaalien mittaamiseen

O objetivo deste estudo foi o desenvolvimento de compósitos poliméricos flexíveis e altamente condutores elétricos preparados por moldagem por compressão e por fabricação de filamentos fundidos (FFF) para possíveis aplicações como materiais piezoresistivos ou piezoelétricos para sensores de compressão. Compósitos baseados em misturas de poli(fluoreto de vinilideno)/poliuretano termoplástico (PVDF/TPU) como matriz e contendo várias frações de negro de fumo-polipirrol (CB-PPy) como aditivo condutor foram preparados. Diversas técnicas de caracterização foram realizadas para avaliar as propriedades mecânicas, térmicas, químicas e elétricas, morfologia e printabilidade dos materiais investigados. Primeiro, blendas de PVDF/TPU com diferentes composições foram produzidas por mistura por fusão seguida de moldagem por compressão. Os resultados mostraram que a flexibilidade desejada para os materiais foi melhorada com a adição de TPU aos compósitos de PVDF. As imagens SEM evidenciaram a obtenção de uma blenda co-contínua com 50/50 vol% de PVDF/TPU. As blendas compostas de PVDF/TPU 38/62 vol% e a blenda co-contínua de PVDF/TPU 50/50 vol% foram selecionadas como matrizes para a preparação de compósitos moldados por compressão e impressos em 3D a fim de alcançar uma ótima combinação entre condutividade, propriedades mecânicas e printabilidade. Várias quantidades de negro de fumo-polipirrol, de 0 a 15%, foram adicionadas às blendas selecionadas para aumentar a condutividade elétrica dos compósitos e possivelmente atuar como agente nucleante para a fase cristalina do PVDF a fim de aumentar sua resposta piezoelétrica. A adição de CB-PPy aumentou a condutividade elétrica de todos os compósitos. No entanto, a condutividade elétrica dos compósitos baseados em blendas co-contínuas PVDF/TPU 50/50 vol% foi maior do que as encontradas para os compósitos de PVDF/TPU 38/62 vol% com mesma concentração de aditivo. De fato, o limiar de percolação elétrico dos compósitos com blenda co-contínua foi de 2%, enquanto o limiar de percolação elétrico dos compósitos compostos da blenda não contínua foi de 5%. Com relação às propriedades mecânicas, a incorporação do aditivo condutor nas blendas resultou em materiais mais rígidos com maior módulo de elasticidade, menor alongamento na ruptura e maior módulo de armazenamento. O módulo de armazenamento (G') e a viscosidade complexa (η*) dos compósitos aumentaram com a adição de CB-PPy. O limiar de percolação reológico foi de 3% para PVDF/TPU/CB-PPy 38/62 vol% e 1% para PVDF/TPU/CB-PPy 50/50 vol%, indicando que uma quantidade maior de carga poderia comprometer a processabilidade dos compósitos. A adição de CB-PPy também resultou na redução dos valores de Tg e Tm dos compósitos devido à redução da mobilidade das cadeias poliméricas. Com base na condutividade elétrica e no comportamento mecânico dos compósitos, três composições diferentes foram selecionadas para a extrusão de filamentos para serem posteriormente utilizados no processo de impressão 3D. No geral, as peças impressas em 3D apresentaram propriedades mecânicas e elétricas inferiores devido à presença de vazios, defeitos e camadas sobrepostas que podem dificultar o fluxo de elétrons. Os valores de condutividade elétrica dos compósitos impressos em 3D de PVDF/TPU/CB-PPy 38/62 vol% contendo 5% e 6% de CB-PPy são de uma a sete ordens de grandeza menores do que os encontrados para os compósitos com a mesma composição moldados por compressão. Mesmo que o valor da condutividade elétrica para o compósito PVDF/TPU 38/62 vol% com 6% de CB-PPy moldado por compressão foi de 1,94x10-1 S•m-1, o compósito impresso em 3D com a mesma composição mostrou um valor muito baixo de condutividade elétrica de 6,01x10-8 S•m-1. Por outro lado, o compósito co-contínuo de PVDF/TPU 50/50 vol% com 10% de aditivo impresso em 3D apresentou um alto valor de condutividade elétrica de 4,14×100 S•m-1 mesmo após o processo de impressão. Além disso, as respostas piezoresistivas dos compósitos foram investigadas. Para os compósitos PVDF/TPU/CB-PPy 38/62 vol%, as amostras moldadas por compressão e impressas em 3D com 5% e 6% de CB-PPy exibiram boa resposta piezoresistiva. No entanto, apenas os compósitos com 6% de aditivo apresentaram valores elevados de sensibilidade e gauge factor, atuação em ampla faixa de pressão e respostas piezoresistivas reprodutíveis durante a aplicação de 100 ciclos de compressão/descompressão para ambos os métodos de fabricação. Por outro lado, para os compósitos co-contínuos de PVDF/TPU/CB-PPy apenas a amostra moldada por compressão com 5% de CB-PPy apresentou respostas piezorresistivas boas e reprodutíveis. A cristalinidade e o teor de fase β do PVDF foram investigados para os compósitos. Embora o grau de cristalinidade das amostras tenha diminuído com a adição de CB-PPy, a porcentagem de fase β no PVDF aumentou. O coeficiente piezoelétrico d33 das amostras aumentou com a porcentagem de fase β. A adição de 6% ou mais de CB-PPy foi necessária para aumentar significativamente o coeficiente piezoelétrico (d33) dos compósitos. O conteúdo de fase β e as respostas piezoelétricas do PVDF foram menores para as amostras preparadas por FFF. Por fim, como pesquisa colateral, a eficiência de blindagem contra interferência eletromagnética (EMI-SE) foi medida para todos os compósitos. Compósitos com maior condutividade elétrica apresentaram melhor blindagem da radiação eletromagnética. Além disso, os compósitos baseados na blenda co-contínua apresentaram maior eficiência de blindagem contra EMI do que os compósitos de PVDF/TPU 38/62 vol%. O principal mecanismo de blindagem foi a absorção para todos os compósitos. As amostras preparadas por FFF apresentaram respostas de EMI-SE menores quando comparadas às amostras moldadas por compressão.
The aim of this study was the development of flexible and highly electrically conductive polymer composites via compression molding and fused filament fabrication for possible applications as piezoresistive or piezoelectric materials for pressure sensors. Composites based on blends of poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) as matrix and containing various fractions of carbon black-polypyrrole (CB-PPy) as conductive filler were prepared. Several characterization techniques were performed in order to evaluate the mechanical, thermal, chemical and electrical properties, morphology and printability of the investigated materials. First, PVDF/TPU blends with different compositions were prepared by melt compounding followed by compression molding. The results showed that the flexibility aimed for the final materials was improved with the addition of TPU to PVDF composites. SEM images evidenced the achievement of a co-continuous blend comprising 50/50 vol% of PVDF/TPU. The blends composed of PVDF/TPU 38/62 vol% and the co-continuous blend of PVDF/TPU 50/50 vol% were selected as matrices for the preparation of compression molded and 3D printed composites in order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability. Various amounts of carbon black-polypyrrole, from 0 up to 15%, were added to the selected blends in order to rise the electrical conductivity of the composites and to possible act as nucleating filler for the β crystalline phase of PVDF in order to increase its piezoelectric response. The addition of CB-PPy increased the electrical conductivity of all composites. However, the electrical conductivity of composites based on PVDF/TPU 50/50 vol% co-continuous blends was higher than those found for PVDF/TPU 38/62 vol% composites at the same filler content. Indeed, the electrical percolation threshold of the conductive co-continuous composite blends was 2%, while the electrical percolation threshold of the composites with the nonco-continuous composite blends was 5%. With respect to the mechanical properties, the incorporation of the filler into the blends leaded to more rigid materials with higher elastic modulus, lower elongation at break and higher storage modulus. The storage modulus (G’) and complex viscosity (η*) of the composites increased with the addition of CB-PPy. The rheological percolation threshold was found to be 3% for PVDF/TPU/CB-PPy 38/62 vol% and 1% for PVDF/TPU/CB-PPy 50/50 vol%, indicating that higher amount of filler could compromise the processability of the composites. The addition of CB-PPy also resulted in a reduction on the Tg and Tm values of the composites due to the reduction of the mobility of the polymeric chains. Based on the electrical conductivity and mechanical behavior of the composites, three different compositions were selected for the extrusion of filaments to be used in a 3D printing process. Overall, the 3D printed parts presented lower mechanical and electrical properties because of the presence of voids, defects and overlapping layers that can hinder the flow of electrons. The electrical conductivity values of PVDF/TPU/CB-PPy 38/62 vol% composites containing 5% and 6 wt% of CB-PPy 3D printed samples are one to seven orders of magnitude lower than those found for compression molded composites with the same composition. Even if the electrical conductivity value for PVDF/TPU 38/62 vol% compression molded composite with 6% of CB-PPy was as high as 1.94x10-1 S•m-1, the 3D printed composite with same composition showed a very low electrical conductivity of 6.01x10-8 S•m-1. On the other hand, the 3D printed co-continuous composite PVDF/TPU 50/50 vol% with 10% of filler displayed a high value of electrical conductivity of 4.14×100 S•m-1 even after the printing process. Moreover, the piezoresistive responses of the composites were investigated. For PVDF/TPU/CB-PPy 38/62 vol% composites, the compression molded and 3D printed samples with 5% and 6% of CB-PPy exhibited good piezoresistive response. However, only the composites with 6% displayed high sensitivity and gauge factor values, large pressure range and reproducible piezoresistive responses under 100 cycles for both methods. On the other hand, for PVDF/TPU/CB-PPy co-continuous composites only the compression molded sample with 5% of CB-PPy presented good and reproducible piezoresistive responses. The crystallinity and β phase content of PVDF were investigated for the composites. Althought the degree of crystallinity of the samples decreased with the addition of CB-PPy, the percentage of β phase in PVDF was increased. The piezoelectric coefficient d33 of the samples increased with the percentage of β phase. The addition of 6% or more of CB-PPy was necessary to increase significatively the piezoelectric coefficient (d33) of the composites. The β phase content and piezoelectric responses of PVDF were lower for samples prepared by FFF. Finally, as a collateral research, the electromagnetic interference shielding effectiveness (EMI-SE) were measured for all composites. Composites with higher electrical conductivity showed better shielding of the electromagnetic radiation. In addition, composites based on the co-continuous blend displayed higher EMI shielding efficiency than 38/62 vol% composites. The main mechanism of shielding was absorption for all composites. Specimens prepared by FFF displayed diminished EMI-SE responses when compared to compression molded samples.
Lo scopo di questo studio è lo sviluppo di compositi polimerici flessibili e ad elevata conducibilità elettrica tramite stampaggio a compressione e manifattura additiva (fused filament fabrication) per possibili applicazioni come materiali piezoresistivi o piezoelettrici in sensori di pressione. In particolare, sono stati preparati compositi a base di miscele di poli(vinilidene fluoruro)/poliuretano termoplastico (PVDF/TPU) come matrice e contenenti varie frazioni di nerofumo-polipirrolo (CB-PPy) come riempitivo conduttivo. Sono state utilizzate diverse tecniche di caratterizzazione al fine di valutare le proprietà meccaniche, termiche, chimiche ed elettriche, la morfologia e la stampabilità dei materiali ottenuti. In primo luogo, miscele PVDF/TPU con diverse composizioni sono state preparate mediante mescolatura allo stato fuso seguita da stampaggio a compressione. I risultati hanno mostrato che la flessibilità del PVDF viene notevolemente migliorata dall’aggiunta di TPU. Le immagini SEM hanno evidenziato il raggiungimento di una miscela co-continua per una composizione 50/50% in volume di PVDF/TPU. Le miscele composte da PVDF/TPU 38/62 vol% e la miscela co-continua di PVDF/TPU 50/50 vol% sono state selezionate come matrici per la preparazione di compositi per stampaggio a compressione e manifattura additiva al fine di ottenere un compromesso ottimale tra conducibilità, proprietà meccaniche e stampabilità. Alle miscele selezionate sono state aggiunte varie quantità di nerofumo-polipirrolo, dallo 0 al 15%, per aumentare la conducibilità elettrica dei compositi ed eventualmente fungere da additivo nucleante per la fase β cristallina del PVDF al fine di aumentarne la risposta piezoelettrica. L'aggiunta di CB-PPy ha aumentato la conduttività elettrica di tutti i compositi. Tuttavia, la conduttività elettrica dei compositi basati su miscele co-continue di PVDF/TPU 50/50% in volume era superiore a quella trovata per compositi PVDF/TPU 38/62% in volume con lo stesso contenuto di riempitivo. Infatti, la soglia di percolazione elettrica delle miscele conduttive era del 2%, mentre la soglia di percolazione elettrica dei compositi con miscele composite non continue era del 5%. Per quanto riguarda le proprietà meccaniche, l'incorporazione del riempitivo nelle mescole ha portato a materiali più rigidi con modulo elastico più elevato, allungamento a rottura inferiore e modulo conservativo più elevato. Il modulo conservativo (G') e la viscosità complessa (η*) dei compositi sono aumentate con l'aggiunta di CB-PPy. La soglia di percolazione reologica è risultata essere del 3% per PVDF/TPU/CB-PPy 38/62 vol% e dell'1% per PVDF/TPU/CB-PPy 50/50 vol%, indicando che una maggiore quantità di riempitivo potrebbe compromettere la processabilità dei compositi. L'aggiunta di CB-PPy ha comportato anche una riduzione dei valori di Tg e Tm dei compositi a causa della riduzione della mobilità delle catene polimeriche. Sulla base della conduttività elettrica e del comportamento meccanico dei compositi, sono state selezionate tre diverse composizioni per l'estrusione di filamenti da utilizzare in un processo di stampa 3D. Nel complesso, le parti stampate in 3D presentavano proprietà meccaniche ed elettriche inferiori a causa della presenza di vuoti, difetti e strati sovrapposti che possono ostacolare il flusso di elettroni. I valori di conducibilità elettrica dei compositi PVDF/TPU/CB-PPy 38/62 vol% contenenti il 5% e il 6% di CB-PPy di campioni stampati in 3D sono da uno a sette ordini di grandezza inferiori a quelli trovati per i compositi stampati a compressione con la stessa composizione. Anche se il valore di conducibilità elettrica per il composito stampato a compressione PVDF/TPU 38/62 vol% con il 6% di CB-PPy era pari a 1,94x10-1 S•m-1, il composito stampato in 3D con la stessa composizione ha mostrato un valore molto basso di conducibilità elettrica, pari a 6,01x10-8 S•m-1. D'altra parte, il composito PVDF/TPU 50/50 vol% stampato in 3D con il 10% di riempitivo ha mostrato un elevato valore di conducibilità elettrica, pari a 4,14 × 100 S•m-1, anche dopo il processo di stampa. Inoltre, sono state studiate le risposte piezoresistive dei compositi. Per i compositi PVDF/TPU/CB-PPy 38/62 vol%, i campioni stampati a compressione e stampati in 3D con il 5% e il 6% di CB-PPy hanno mostrato una buona risposta piezoresistiva. Tuttavia, solo i compositi con il 6% hanno mostrato valori di sensibilità e gauge factor elevati, ampio intervallo di pressione e risposte piezoresistive riproducibili in 100 cicli per entrambi i metodi. D'altra parte, per i compositi co-continui PVDF/TPU/CB-PPy solo il campione stampato a compressione con il 5% di CB-PPy ha presentato risposte piezoresistive adeguate e riproducibili. La cristallinità e il contenuto di fase β del PVDF sono stati studiati per i compositi. Sebbene il grado di cristallinità dei campioni diminuisca con l'aggiunta di CB-PPy, la percentuale di fase β in PVDF risulta aumentata. Il coefficiente piezoelettrico d33 dei campioni aumenta anch’esso con la percentuale di fase β. L'aggiunta del 6% o più di CB-PPy è stata necessaria per aumentare significativamente il coefficiente piezoelettrico (d33) dei compositi. Il contenuto di fase β e le risposte piezoelettriche del PVDF sono inferiori per i campioni ottenuti mediante stampa 3D. Infine, come ricerca collaterale, è stata misurata l'efficacia della schermatura contro le interferenze elettromagnetiche (EMI-SE) per tutti i compositi. I compositi con una maggiore conduttività elettrica hanno mostrato una migliore schermatura della radiazione elettromagnetica. Inoltre, i compositi basati sulla miscela co-continua hanno mostrato un'efficienza di schermatura EMI maggiore rispetto ai compositi a 38/62% in volume. Per tutti i compositi, il principale meccanismo di schermatura è l'assorbimento. I campioni preparati mediante manifattura additiva hanno mostrato risposte EMI-SE inferiori rispetto ai campioni stampati a compressione.

The ability of a piezoelectric transducer in energy conversion is rapidly expanding in several applications. Some of the industrial applications for which a high power ultrasound transducer can be used are surface cleaning, water treatment, plastic welding and food sterilization. Also, a high power ultrasound transducer plays a great role in biomedical applications such as diagnostic and therapeutic applications. An ultrasound transducer is usually applied to convert electrical energy to mechanical energy and vice versa. In some high power ultrasound system, ultrasound transducers are applied as a transmitter, as a receiver or both. As a transmitter, it converts electrical energy to mechanical energy while a receiver converts mechanical energy to electrical energy as a sensor for control system. Once a piezoelectric transducer is excited by electrical signal, piezoelectric material starts to vibrate and generates ultrasound waves. A portion of the ultrasound waves which passes through the medium will be sensed by the receiver and converted to electrical energy. To drive an ultrasound transducer, an excitation signal should be properly designed otherwise undesired signal (low quality) can deteriorate the performance of the transducer (energy conversion) and increase power consumption in the system. For instance, some portion of generated power may be delivered in unwanted frequency which is not acceptable for some applications especially for biomedical applications. To achieve better performance of the transducer, along with the quality of the excitation signal, the characteristics of the high power ultrasound transducer should be taken into consideration as well. In this regard, several simulation and experimental tests are carried out in this research to model high power ultrasound transducers and systems. During these experiments, high power ultrasound transducers are excited by several excitation signals with different amplitudes and frequencies, using a network analyser, a signal generator, a high power amplifier and a multilevel converter. Also, to analyse the behaviour of the ultrasound system, the voltage ratio of the system is measured in different tests. The voltage across transmitter is measured as an input voltage then divided by the output voltage which is measured across receiver. The results of the transducer characteristics and the ultrasound system behaviour are discussed in chapter 4 and 5 of this thesis. Each piezoelectric transducer has several resonance frequencies in which its impedance has lower magnitude as compared to non-resonance frequencies. Among these resonance frequencies, just at one of those frequencies, the magnitude of the impedance is minimum. This resonance frequency is known as the main resonance frequency of the transducer. To attain higher efficiency and deliver more power to the ultrasound system, the transducer is usually excited at the main resonance frequency. Therefore, it is important to find out this frequency and other resonance frequencies. Hereof, a frequency detection method is proposed in this research which is discussed in chapter 2. An extended electrical model of the ultrasound transducer with multiple resonance frequencies consists of several RLC legs in parallel with a capacitor. Each RLC leg represents one of the resonance frequencies of the ultrasound transducer. At resonance frequency the inductor reactance and capacitor reactance cancel out each other and the resistor of this leg represents power conversion of the system at that frequency. This concept is shown in simulation and test results presented in chapter 4. To excite a high power ultrasound transducer, a high power signal is required. Multilevel converters are usually applied to generate a high power signal but the drawback of this signal is low quality in comparison with a sinusoidal signal. In some applications like ultrasound, it is extensively important to generate a high quality signal. Several control and modulation techniques are introduced in different papers to control the output voltage of the multilevel converters. One of those techniques is harmonic elimination technique. In this technique, switching angles are chosen in such way to reduce harmonic contents in the output side. It is undeniable that increasing the number of the switching angles results in more harmonic reduction. But to have more switching angles, more output voltage levels are required which increase the number of components and cost of the converter. To improve the quality of the output voltage signal with no more components, a new harmonic elimination technique is proposed in this research. Based on this new technique, more variables (DC voltage levels and switching angles) are chosen to eliminate more low order harmonics compared to conventional harmonic elimination techniques. In conventional harmonic elimination method, DC voltage levels are same and only switching angles are calculated to eliminate harmonics. Therefore, the number of eliminated harmonic is limited by the number of switching cycles. In the proposed modulation technique, the switching angles and the DC voltage levels are calculated off-line to eliminate more harmonics. Therefore, the DC voltage levels are not equal and should be regulated. To achieve this aim, a DC/DC converter is applied to adjust the DC link voltages with several capacitors. The effect of the new harmonic elimination technique on the output quality of several single phase multilevel converters is explained in chapter 3 and 6 of this thesis. According to the electrical model of high power ultrasound transducer, this device can be modelled as parallel combinations of RLC legs with a main capacitor. The impedance diagram of the transducer in frequency domain shows it has capacitive characteristics in almost all frequencies. Therefore, using a voltage source converter to drive a high power ultrasound transducer can create significant leakage current through the transducer. It happens due to significant voltage stress (dv/dt) across the transducer. To remedy this problem, LC filters are applied in some applications. For some applications such as ultrasound, using a LC filter can deteriorate the performance of the transducer by changing its characteristics and displacing the resonance frequency of the transducer. For such a case a current source converter could be a suitable choice to overcome this problem. In this regard, a current source converter is implemented and applied to excite the high power ultrasound transducer. To control the output current and voltage, a hysteresis control and unipolar modulation are used respectively. The results of this test are explained in chapter 7.

This thesis presents mathematical modeling and control techniques that can be used to predict and specify performance of biologically inspired actuation systems called cellular actuators. Cellular actuators are modular units designed to be connected in bundles in manner similar to human muscle fibers. They are characterized by inherent compliance and large numbers of on-off discrete control inputs. In this thesis, mathematical tools are developed that connect the performance to the physical manifestation of the device. A camera positioner inspired by the human eye is designed to demonstrate how these tools can be used to create an actuator with a useful force-displacement characteristic. Finally, control architectures are presented that use discrete switching inputs to produce smooth motion of these systems despite an innate tendency toward oscillation. These are demonstrated in simulation and experiment.

In this thesis, an attitude control system based on Linear Quadratic Regulator (LQR) technique is developed for a hypothetical Earth observation satellite with a long flexible boom. To improve pointing performance of the satellite, the piezoelectric actuators are used as well. The boom is rectangular made of aluminum with the surface bonded piezoelectric layers on all four surfaces. The boom is modeled using finite elements. The pointing performance of the satellite using various metrics is evaluated through simulations. Effectiveness of the piezoelectric actuators is demonstrated.

Ce travail porte sur la réalisation de capteurs interdigités (IDT pour InterDigital Transducer) sur des supports piézoélectriques. L’enjeu est double puisqu’il s’agit premièrement de disposer de capteurs efficaces pour générer des ondes de surface acoustiques (SAW pour Surface Acoustic Wave) afin de caractériser la qualité des revêtements et des surfaces de structures. Le deuxième objectif de cette étude est de rendre ces capteurs IDT flexibles afin qu’ils puissent s’adapter non seulement aux différentes géométries planes ou non mais aussi pour qu’ils soient capables de supporter les déformations des structures au cours de leur utilisation. En général, les matériaux piézoélectriques sont rigides et le caractère souple des matériaux est souvent en opposition avec les performances piézoélectriques de ces derniers ; nous avons donc développé des matériaux qui répondent à ces deux exigences : la performance piézoélectrique et la souplesse. Enfin, nous avons privilégié des technologies relativement bon marché pour développer ces capteurs afin d’envisager par la suite, un contrôle continu des structures en intégrant ces capteurs à demeure sur ces dernières
This work deals with the realization of interdigital sensors (IDT for InterDigital Transducer) on piezoelectric substrates. There is a dual challenge since firstly, the aim is to have efficient sensors to generate surface acoustic waves (SAW) in order to characterize the quality of the coatings and structure surfaces. The second objective of this study is to make these IDT sensors flexible so as to adapt to different geometries of structures and to be able to put up with the deformations of structures in use. Typically, piezoelectric materials are rigid and the flexible nature of the materials is often in opposition to the piezoelectric performance of the latter. We developed materials that meet these two requirements: piezoelectricity and flexibility. Finally, we gave greater importance to relatively cheap technologies to develop these sensors because this allows then to consider continuous monitoring (structural health monitoring) by incorporating these sensors permanently on the structures to be tested

This work consists in the development and design of an energy harvesting device to supply power to the new generation pacemakers, miniaturized leadless implants without battery placed directly in heart chambers. After analyzing different mechanical energy sources in the cardiac environment and associated energy harvesting mechanisms, a concept based on regular blood pressure variation stood out: an implant with a flexible packaging that transmits blood forces to an internal transducer. Advantages compared to traditional inertial scavengers are mainly: greater power density, adaptability to heartbeat frequency changes and miniaturization potential. Ultra-flexible 10-µm thin metal bellows have been designed, fabricated and tested. These prototypes acting as implant packaging that deforms under blood pressure actuation have validated the proposed harvesting concept. A new type of electrostatic transducer (3D multi-layer out-of-plane overlap structure with interdigitated combs) has been introduced and fully analyzed. Promising numerical results and associated fabrication processes are presented. Also, large stroke optimized piezoelectric spiral transducers including their complex electrodes patterns have been studied through a design analysis, numerical simulations, prototype fabrication and experimental testing. Apower density of 3 µJ/cm3/cycle has been experimentally achieved. With further addressed developments, the proposed device should provide enough energy to power autonomously and virtually perpetually the next generation of pacemakers.

Les NWs de ZnO hautement résistifs sont destinés à être utilisés comme capteurs de pression dans des substrats flexibles. Pour cela, il était important de développer le rôle important des défauts liés à l'hydrogène et à l'azote dans les NWs de ZnO cultivés par CBD, comme cela a été largement étudié dans cette thèse. Le chapitre 1 détaille l'état de l'art de la présente thèse et le chapitre 2 détaille les procédures expérimentales utilisées pour développer les différentes études de cette thèse. Dans le chapitre 3, la conduction électrique de type métallique des NWs de ZnO cultivés spontanément a été attribuée à une forte densité de porteurs de charge libre due aux défauts liés à l'hydrogène (c'est-à-dire le HBC et le VZn-3H agissant comme des donneurs superficiels). Ensuite, le chapitre 4 démontre la capacité d'ingénierie des NWs de ZnO par recuit thermique sous une atmosphère d'oxygène, montrant que la densité des défauts liés à l'hydrogène diminue à ~300 °C, et que l'activation thermique de VZn-NO-H (agissant comme accepteur profond) à ~450 °C favorise une compensation importante. De plus, l'incorporation intentionnelle d'atomes dopants de Sb dans les NWs de ZnO apporte une nouvelle approche en réalisant les croissances dans les régions à faible et à fort pH, comme cela a été fait dans le chapitre 5. Ainsi, le chapitre 6 élucide la modulation complexe entre les défauts liés à l'hydrogène, à l'azote et à l'antimoine dans les différentes conditions de croissance et de recuit. En particulier, le nouveau recuit en deux étapes à 300 °C pendant 4 heures et une heure consécutive à 450 °C illustre la possibilité de diffuser exogène les donneurs d'hydrogène et d'activer thermiquement les défauts liés au VZn-NO-H et au Sb. Enfin, le chapitre 7 montre l'incorporation de ces NWs de ZnO hautement résistifs comme capteurs piézoélectriques flexibles
Highly resistive ZnO NWs are intended for their application as pressure sensors in flexible substrates. To achieve this, it was important to develop the important role of hydrogen- and nitrogen-related defects in ZnO NWs grown by CBD, as it has been extensively studied in this thesis. Chapter 1 details the state-of-the-art of the present thesis and Chapter 2 details the experimental procedures used to develop the different studies of this thesis. In Chapter 3, the metal-like electrical conduction of spontaneously grown ZnO NWs was attributed to a high density of free charge carriers due to hydrogen-related defects (i.e., HBC and VZn-3H acting as shallow donors). Then, Chapter 4 demonstrates the capacity to engineer the ZnO NWs by thermal annealing under an oxygen atmosphere, showing that the density of hydrogen-related defects would decrease at ~300 °C, and the thermal activation of VZn-NO-H (acting as deep acceptor) at ~450 °C would promote an important compensation. Furthermore, the intentional incorporation of Sb dopant atoms in the ZnO NWs bring a novel approach by performing the growths in the low- and high-pH regions, as performed in Chapter 5. Hence, Chapter 6 elucidates the complex modulation between the hydrogen-, nitrogen- and antimony-related defects at the different growth conditions and the different annealing conditions. Particularly, the novel two-step annealing at 300 °C for 4 h and a consecutive 1 h at 450 °C will illustrate the possibility to exo diffuse the hydrogen-donors and thermally activate the VZn-NO-H and Sb-related defects. Finally, Chapter 7 shows the incorporation of these highly resistive ZnO NWs as flexible piezoelectric sensors

碩士
逢甲大學
電聲碩士學位學程
100
Modern audio and video towards thinner and miniaturization, for example: phone, TV, Tablet PC ... etc., flat speaker came into being. Goals for the research and development of this thesis, a flexible and thin speaker polymer piezoelectric film PVDF with flexible features due to PVDF. The goal of this thesis for the analysis of various parameters of the flexible piezoelectric thin speaker frequency response curve parameters There are four, including the the PVDF thickness diaphragm material, piezoelectric-driven approach and speaker shape. The parameters are set as follows PVDF thickness of 130μm and 40μm, diaphragm materials include polypropylene (PP), poly-ethylene terephthalate ester (PET), polyethylene naphthalate ethylene naphthalate (PEN), and aluminum foil, the piezoelectric The drive mode is divided into the unimorph drive and double-layer piezoelectric drive, and finally change its speaker shape is planar and the arc-shaped. Portion of the speaker measured in the anechoic chamber by Sound Check instrument for all the parameters measured, compare four parameters and frequency in response to the relationship between the curve in the diagram of the final use of the measured data, identify the piezoelectric flexible thin speaker the best parameters that will be an important basis for the future development of flexible piezoelectric thin speaker.

碩士
國立中興大學
機械工程學系所
100
In this study, a single-mode piezoelectric sensor for the detection of low-frequency vibration mechanical failure is developed. To have the single-mode sensor to be operated at low frequency, we deposited the PZT-silica composite films on a PI-copper flexible substrate at 150C by sol-gel technology. The advantage of using low-frequency single-mode sensor for the detection of mechanical failure is that no extra signal process system is required and vibration is able to be estimated by the output voltage directly in order to enhance the practicability and reduce the system cost. Experimental result showed that developed sensors operated at 76Hz. When the frequency is shifted by 5HZ, the sensitivity plummets by 50%. Due to the significant change, we can tell whether the vibration frequency of low-frequency machineries is shifted. As for the output, the sensitivity of sensors is large than 60mV/g. The sensors also were able to be used at large deflection test. After repetitions of testing, the change of sensitivity was less than 10%. Thus, when knocking occurs, our sensor has better endurance. The sensor output was able to detect vibration at specific frequency by scaling the signal and the signal process system could be simplified instead of using the spectrum technique. Keyword: Single-mode, flexible, low-frequency, piezoelectric sensor

In recent decades, there has been increasing interest in the development of new materials in order to achieve the "Internet of Things (IoT)" which provided for the connection of 20 to 30 billion devices to the Internet by 2020. The implementation of the "Internet of Things "requires the development of base technology, which includes transducers, actuators and sensors. Sensors are often used in biomedical applications that require flexibility, biocompatibility and sustainability. In this context, the motivation of this work was the preparation of a bionanocomposite for biocompatible piezoelectric sensors for biomedical applications. Thus, a polysaccharide that have the ability to form films (films), and particles of barium titanate which is ferroelectric and piezoelectric material at room temperature, having no lead in its composition. The BaTiO3 particles were synthesized by hydrothermal method at moderate temperature (200 °C) and in the absence of organic solvents. Several reaction times were studied in order to select the ideal conditions for the particles preparation with the required properties to be incorporated in the chitosan-based films. The structural characterization by X-ray diffraction (XRD) and Raman spectroscopy allowed us to verify that the particles synthesized at 200 °C showed a well-defined tetragonal crystallographic structure after 24 hours of synthesis. The particles showed uniformed cubic morphology and average size of about 306 nm. In general, particle and crystallite sizes increase with reaction time. The films were obtained by the solvent evaporation method, after dispersing the particles in different proportions, in a solution of chitosan. Structural properties (XRD) and morphological (SEM); physical-chemical (mechanical, degree of humidity, solubility in water and contact angle, and Raman); and electrical (dielectric behavior, hysteresis curves and nanoscale piezoelectric response) of the films were characterized. The addition of particles improved the mechanical properties of the chitosan films, making them more resistant, elastic and ductile. These films have also been shown to be more resistant to water, which reveals that there is an interaction between the particles and the chitosan matrix. In relation to the electric behavior of the films, the increase of particles improves the permittivity of the samples five times in relation to the biopolymer material. It was verified a great difficulty of deposition of electrodes in the flexible films that can be justified on the basis of the characteristics of the samples and / or the inadequacy of the experimental conditions of deposition of the electrodes in the sample. It was not possible to measure the piezoelectric response at the macroscopic scale nor to polarize an area of the bionanocomposite sample. Thus, the piezoelectric response at the nanometric scale was studied by atomic microscopy of piezoelectric response. It was found that nanocomposite films with the highest concentration of nanoparticles clearly showed piezoelectric domains, but it is not possible to obtain an acceptable hysteresis curve and to polarize a small area of the nanocomposite. These observations, together with the analysis by surface potential microscopy of the control film (chitosan only) that indicates the presence of charges in the pure polymer, lead to the conclusion of an electret type behavior, being necessary a strategy to eliminate (or reduce) the matrix's contribution. Despite the difficulties encountered due to degree of innovation of the work, the bionanocomposites developed based on chitosan and barium titanate are promising to be used in biomedical devices (drug release pads, etc.) since they have high mechanical resistance, elasticity, and ductility, as well as have higher resistance to conditions with high degree of humidity. In addition, they are biocompatible and partially biodegradable, being an excellent alternative to synthetic polymers
Nas últimas décadas, tem havido um interesse crescente no desenvolvimento de novos materiais com o intuito de alcançar a "Internet of Things (IoT)" que prevê a ligação de 20 a 30 bilhões de dispositivos à internet até 2020. A implementação da “Internet of Things” exige o desenvolvimento de tecnologia base, onde se incluem os dispositivos de captação de energia, atuadores e sensores. Os sensores são muitas vezes utilizados em aplicações biomédicas que exigem flexibilidade, biocompatibilidade e sustentabilidade. Neste contexto, a motivação deste trabalho foi a preparação de um bionanocompósito para sensores piezoelétricos biocompatíveis para aplicações biomédicas. Assim, escolheu-se como matriz um polissacarídeo que tem a capacidade de formar películas (filmes) facilmente, e partículas de titanado de bário que é um material ferroeléctrico e piezoeléctrico à temperatura ambiente, não possuindo chumbo na sua composição. As partículas de BaTiO3 foram sintetizadas por método hidrotermal a temperatura moderada (200 °C) e na ausência de solventes orgânicos. Foram estudadas vários tempos de reação de forma a selecionar as condições ideais para a preparação das partículas com as propriedades adequadas para a incorporação nos filmes à base de quitosana. A caracterização estrutural por difração de raios-X (DRX) e espectroscopia de Raman permitiu verificar que as partículas sintetizadas a 200 °C apresentavam, ao fim de 24 horas de síntese, a estrutura cristalográfica tetragonal bem definida. As partículas mostraram morfologia cúbica uniforme e tamanho médio de cerca de 306 nm. Em geral, os tamanhos das partículas e de cristalites aumentam com o tempo de reação. Os filmes foram obtidos pelo método de evaporação de solvente, após a dispersão das partículas, em diferentes proporções, numa solução de quitosana. As propriedades estruturais (DRX) e morfológicas (SEM); físico-químicas (mecânicas, grau de humidade, solubilidade em água e ângulo de contacto e Raman); e elétricas (comportamento dieléctrico, curvas de histerese e resposta piezoelétrica à escala nanométrica) dos filmes foram caracterizadas. A adição de partículas melhorou as características mecânicas dos filmes de quitosana, tornando-os mais resistentes, elásticos e dúcteis. Estes filmes revelaram também serem mais resistentes à água, o que revela que existe uma interação entre as partículas e a matriz de quitosana. Em relação ao comportamento elétrico dos filmes, o aumento de partículas melhora a permitividade das amostras cinco vezes em relação ao material biopolimérico. Foi verificada uma grande dificuldade de deposição de elétrodos nos filmes flexíveis que se pode justificar com base nas características das amostras e/ou na inadequação das condições experimentais de deposição dos elétrodos na amostra. Como não foi possível medir a resposta piezoeléctrica à escala macroscópica, nem polarizar uma área da amostra de bionanocompósito, fez-se o estudo da resposta piezoelétrica à escala nanométrica por microscopia atómica de resposta piezoelétrica. Os filmes com a concentração mais elevada de nanopartículas mostraram claramente domínios piezoelétricos, não sendo, contudo, possível traçar uma curva de histerese aceitável nem polarizar uma pequena área do nanocompósito. Esta observação, juntamente com a análise por microscopia de potencial de superfície do filme controlo (só de quitosana) que indica a presença de cargas no polímero puro, leva à conclusão da existência de um comportamento do tipo electret pelo que será necessário encontrar uma estratégia para eliminar (ou reduzir) a contribuição da matriz. Apesar das dificuldades encontradas, os bionanocompóstos desenvolvidos, à base de quitosana e titanato de bário são promissores para serem usados em dispositivos biomédicos (por exemplo em compressas para libertação de fármacos, etc.) devido à sua elevada resistência mecânica, elasticidade e ductilidade, sendo adaptados a condições de elevado grau de humidade. Estes bionanocompósitos são ainda biocompatíveis e parcialmente biodegradáveis, tendo potencial para serem usados como alternativa aos polímeros sintéticos
Mestrado em Materiais e Dispositivos Biomédicos

碩士
南台科技大學
機械工程系
95
The tactile sensor has flexible characteristic that it can be applied in the application with the human body physiological monitoring for example，pulse, heartbeat, blood pressure. However the piezoelectric-type tactile sensor sensitivity needs to be improved. Therefore we introduce the concept of structural electrode for enhancement of the sensitivity of piezoelectric tactile sensor and fabricated structure by MEMS process. A sandwich structure for flexible tactile sensor consists of top and bottom soft substrates made of Polystyrene, and in between of two soft substrates a piezoelectric thin film, PVDF, and patterned different area, are utilized as sensing material and microstructures, respectively and used shaker and force sensor. We design our experiment of tactile sensing system. The signal of a contact pressure to the tactile sensor are sensed and processed in the DAQ System. Finally the signals are integrated for taking the force profile. The processed signals of the output of the sensor are visualized on LabVIEW in personal computer in real time. A rudimentary tactile object image measurement procedure for applied loads has been devised to recognize the silhouette of a sharp edge, square, ,circle, the shape and force distribution of the contact object are obtained using two and three-dimensional image in real time.

碩士
國立宜蘭大學
機械與機電工程學系碩士班
101
VDF, a piezoelectric polymer, is suitable for flexible devices because of its flexibility and lightweight. In this article, the authors adopt commercial PVDF film to make a film loudspeaker. The proposed film loudspeaker is a sandwiched membrane structure which contains a PVDF film sandwiched in between two silver electrode-layers. An audio signal is applied to the PVDF film, which responds by the mechanical deflection in proportion to the voltage applied across the PVDF film, thus converting electrical energy into mechanical vibration. Therefore, the coupled electromechanical characteristic of the compound membrane dominates the performance of the loudspeaker. This work is to find the resonant frequencies and vibration mode shapes of the proposed PVDF film loudspeaker as well as its frequency response over the audible range (20 Hz – 20 kHz). To measure the dynamic response of the PVDF film loudspeaker to driving voltage, the authors make a test frame by acrylic plates. The PVDF film loudspeaker is clamped in the test frame by four screws. A sine-wave AC voltage is applied on the PVDF film loudspeaker by a function generator. The driving frequencies are scanned in the audible range, namely 20 Hz to 20 kHz. The vibration of the PVDF film loudspeaker is measured by a laser Doppler Vibrometer. This article studies on the coupled electromechanical characteristic of the compound membrane of the PVDF film loudspeaker. In the near future, the design of the PVDF film loudspeaker can be optimized according to the results of this work.

碩士
國立虎尾科技大學
光電與材料科技研究所
97
The ZnO nanostructures were synthesized on flexible soft substrate using chemical deposition methods. We applied the epitaxial growth to produce ZnO nanorods and assembled the nanogenerator with the nanorods. ZnO nanostructures were grown using liquid solution epitaxial method. In liquid epitaxial, effects of growth temperatures, growth times, and growth concentrations on the morphology and characteristics of ZnO nanorods were discussed. The results showed when the temperatures increased, the diameters of the nanowires increased. The XRD results found that the ZnO nanowires had monocrystalline (0002) structure. The ZnO nanostructures had good peak values in ultraviolet emission and blue emission. Finally, making on top of electrode to fabricate nanogenerator with ZnO nanorods and measured micro-current driven by ultrasonic waves, and measuring its voltage and current characteristics. To explore how different deflections of the electromechanical characteristics change with the state of bending in the substrate.

碩士
國立臺南大學
電機工程學系碩博士班
102
In this study, the S doped ZnO nanowires were successfully synthesized on flexible PET substrate by hydrothermal. The crystalline structure of these S doped samples were measured with SEM, EDS, XRD, PL and TEM. The doping concentration of sulfur into ZnO nanowires was 2.03 atm % in EDS. All XRD peaks of S doped ZnO shift to smaller angle. Photoluminescence spectra of S-doped ZnO nanowires show blue shift phenomenon of the green emissions compared with that of pure ZnO nanowires. By TEM EDS-Mapping analysis, we also can see that the S atomic were uniform distributed over the ZnO nanowires. In the S doped ZnO nanowires on flexible PET substrate, we combined it with device for measured the piezoelectric properties with different relative humidity (RH) and different temperature conditions. We also measured the piezoelectric properties with different relative humidity and used the 365nm UV lamp to discuss its resistance variation. In the last section, we used environmental vibration for driving our device to measure with different strain and 365nm UV lamp conditions to investigate the piezoelectric properties of it.

Piezoelectric actuators have proven to be useful in suppressing disturbances and shape control of flexible structures. Large space structures such as solar arrays are susceptible to large amplitude vibrations while in orbit. Moreover, Shape control of many high precision structures such as large membrane mirrors and space antenna is of great importance. Since most of these structures need to be ultra-light-weight, only a limited number of actuators can be used. Consequently, in order to obtain the most effcient control system, the locations of the piezoelectric elements as well as the feedback gain should be optimized. These optimization problems are generally non-convex. In addition, the models for these systems typically have a large number of degrees of freedom. Researchers have used numerous optimization criteria and optimization techniques to find the optimal actuator locations in structural shape and vibration control. Due to the non-convex nature of the problem, evolutionary optimization techniques are extensively used. However, One drawback of these methods is that they do not use the gradient information and so convergence can be very slow. Classical gradient-based techniques, on the other hand, have the advantage of accurate computation; however, they may be computationally expensive, particularly since multiple initial conditions are typically needed to ensure that a global optimum is found. Consequently, a fast, yet global optimization method applicable to systems with a large number of degrees of freedom is needed. In this study, the feedback control is chosen to be an optimal linear quadratic regulator. The optimal actuator location problem is reformulated as a convex optimization problem. A subgradient-based optimization scheme which leads to the global solution of the problem is introduced to optimize the actuator locations. The optimization algorithm is applied to optimize the placement of piezoelectric actuators in vibration control of flexible structures. This method is compared with a genetic algorithm, and is observed to be faster in finding the global optimum. Moreover, by expanding the desired shape into the structure’s modes of vibration, a methodology for shape control of structures is presented. Applying this method, locations of piezoelectric actuators on flexible structures are optimized. Very few experimental studies exist on shape and vibration control of structures. To the best knowledge of the author, optimal actuator placement in shape control has not been experimentally studied in the past. In this work, vibration control of a cantilever beam is investigated for various actuator locations and the effect of optimal actuator placement is studied on suppressing disturbances to the beam. Also using the proposed shape control method, the effect of optimal actuator placement is studied on the same beam. The final shape of the beam and input voltages of actuators are compared for various actuator placements.

碩士
國立海洋大學
機械與輪機工程學系
88
Abstract The purpose of this study is to control the vibration of a flexible beam end point by using piezoelectric actuators. Strain gauge is used to measure the defection of the flexible arm. Encoder is used for measuring motor shaft angular position. The digital controller is implemented in a PC and the controller commands are send to motor driver and piezoelectric amplifier via D/A interface card to suppress vibration of the flexible beam. Euler-Bernoulli beam theory is used to derive the dynamic equations, while the parameters are identified from experimental data. The motor dynamic is controlled by a PID controller. The active beam vibration suppression is done by time-optimal control and PID control and uses a piezoelectric bimorph as actuator. The use of motor as the sole actuator in both rotation and vibration suppression is also studied. Results show that the decay rate is faster when using motor as actuator, but a small vibration will sustain. In contrast, using piezoelectric actuator results in a better settling time performance but a slower initial decay rate.

碩士
南台科技大學
機械工程系
98
The traditional moving-coil loudspeaker has Omni-directional sound field, the sound like the radiating proliferation not have directional characteristics, when the loudspeaker at full volume maybe creates other people puzzle，so in this research we study a directional loudspeaker . Micromachined acoustic devices are recently being focused on the light 、thin and flexible. However, the traditional moving-coil loudspeaker has the limitation on size reduction due to the magnet, coils and horn-type diaphragm. For this reason the piezoelectric loudspeaker very important, On the other hand, piezoelectric loudspeaker not only can generate good quality of sound with planar diaphragm structure but also has the possibility of integration with micromachining technologies. In principle if the loudspeaker sound area is bigger its sound pressure relativity bigger, but the sound area are finite in Consuming electronic product, so this research objective is using directional Loudspeaker Array in finite area and increase the piezoelectric loudspeaker low frequency response. In this study using planar diaphragm structure. In order to enhance the sound pressure level in the low frequency range, a polymer-based piezoelectric thin film (PVDF) was utilized in this study instead of ceramic piezoelectric material such as PZT. In addition, a ring-type bimorph piezoelectric transducer was designed to excite a thin film, this structure has strengthens effect of the piezoelectricity, and using the different vibration membrane to product measure different structure sound pressure. In addition, This research using Huygens function in same area 、 same measure distance and change the point source(n)、frequency, using AM modulation technologies observation the beam pattern. In this experimental result, a ring-type bimorph piezoelectric transducer us different membrane can increase the sound pressure. The piezoelectric speaker increases point souse its spacing is smaller or equal to the wave length(λ) Will concentrate principal part of angle effectively the sound field and restrains side lobes , promotion directional characteristic. When sound area is fixed the point source integer will increase the sound pressure value is reduce, and using AM modulation the sound pressure will weaken about 17 db , but using AM modulation single can promote the main lobe to centralize and to reduce the side lobes angle. Therefore using AM modulation and change the point source spacing to promotion the directional effect.

碩士
國立中正大學
機械工程系研究所
107
This paper mainly studies the design, production and application of acoustic emission (AE) sensors with the characteristics of piezoelectric materials and telescopic and resilience. The AE sensing element has a two-layer structure, and magnets adhere to bottom of both layer to transmit the force, and the AE signal is enhanced by the mutual repulsive force effect of the magnet. The structure of the lower serpentine piezoelectric element is flexible, and this feature enables the sensor to be applied to a curved object to be tested. In addition, the contact force between the object to be tested and the sensor can be measured by a change in the characteristics of the structure of the upper layer. Piezoelectric materials also have the property of capacitance. The characteristics of the piezoelectric material are combined with the serpentine design to make the force sensing element. The circuit is used to convert the capacitance into voltage during the test. Compare the capacitor with the piezoelectric signal.

碩士
國立臺灣大學
工程科學及海洋工程學研究所
105
Based on World Health Organization (WHO), cardiovascular diseases are the number one cause of death globally; more people has died annually from cardiovascular diseases than from any other cause. It is estimated 17.5 million people died from cardiovascular diseases in 2012, representing 31% of all global death. Of these death, an estimated 7.4 million were due to coronary heart disease and 67 million were due to stroke. Over three quarters of cardiovascular diseases’ deaths take place in low and middle income countries. Traditionally, heart related activity monitoring is done by stethoscope or electrogram and by the monitored result, medical personnel could make a decision based on the outcome. However, with the present of flexible lightweight micro-sensor, it gives the user the convenient of measuring the heart activity without making an appointment for medical checkup, moreover, because of the accessible price of this device, it would help to decrease the cardiovascular diseases, especially among the middle and lower class. This thesis presents the fabrication method of piezoelectric sensor on flexible substrate using screen-printing deposition method so that the fabricated sensor has the ability to conform into curved contour to the shape of significant objects. To achieve the unique properties, the deposited piezo-ceramic sensor is transferred to from high temperature stainless steel to flexible substrate. The fabrication process of sensor will be explained in detail, including: the fabrication process, material analysis and the heart pulse measurement result.

碩士
國立臺灣海洋大學
機械與機電工程學系
94
A considerable amount of research work has been done on the application of piezoelectric materials. The number of research papers increases rapidly in the recent years on the use of piezoelectric actuators for structural vibration control. This study applies piezoelectric actuators to control the vibration of a cantilever beam by using active control techniques. The finite element method is applied to obtain the motion equations of a cantilever beam and the attached piezoelectric actuator. The independent modal space control (IMSC) is utilized to control a system with real modes. A single mode control is considered as the baseline analysis case. The mode switching control is consequently applied to control one of the first two modes of the beam system. A combined control force which controls the first two modes simultaneously is further examined. The analysis results show that the mode switching control performs better in the present system. Therefore, it is considered in the further study of the beam system possessing complex modes with the base support damping being taken into account. This study shows that the control spillover is quite serious for systems with close modes when a single mode control is applied, whereas the mode switching control can effectively suppress excessive vibration of the beam system. Keyword: piezoelectric inertia actuators, independent modal space control, active vibration control

碩士
中原大學
機械工程學系
85
The object of the thesis is to study the vibration and contact behaviors of the ultrasonic motor (USM) which uses the piezoelectrically excited mechanical oscillations of a resonator to drive a rotor. In the driving process, we can analysis the nonlinear vibration of a fiexed-free piezoelectrib beam and the contact forces between the stator and the rotor. A purely longitudinally oscillating rod which is positioned on a rotor is excited by a monomodal motor. While a bimodal motor, which operates using only one power amplifier, uses two simultaneously excited modes to drive the rotor, a longitudinal and a flexural modes. The extended Hamilton''s principle is used to derive the equations and the finite element method is used to approximate the equations, yielding a set of non-linear ordinary differential equations. The equations of motion describing the vibrations and contact behavior are derived by Hamilton''s principle and the geometry constraint. The Lagrange multiplier method is used to treat the frictional contact problem. The finite element method and numerical integration scheme are used to simulate the dynamic response of this system with and without contact. Some important factors are studied for the bimodal ultrasonic motor design. The factors include structure design, amplitude of input voltage, phase displacement, exciting frequency and contact behavior.

碩士
國立臺灣大學
應用力學研究所
106
In this thesis, we develop a strain sensor that can provide a real-time monitoring of dynamic large deformation. In short, a electrospun P(VDF-TrFE) piezoelectric fiber strip composed of multiple nanofibers is used to convert the mechanical force into electronic signals. Due to the geometrical microstructure of electrospun strip, this strain sensor is highly flexible and can be used to measure strain within 65 %. To optimize its performance, piezoelectric strips with different electrospinning parameters are fabricated and studied. Experimental results demonstrated mechanical properties of electrospun strips are highly dependent on electrospinning parameters. Experimental results on durability and the level of large strain measurement are discussed in this thesis. Scanning electron microscope was used to exam geometrical microstructure of electrospun strip. A PMMA clamping system was used to provide for quantitative stretchability test. 4 point bending test device which drive by vibrating shaker were applied to verify the reversibility test. Quantitative tensile test devices which drive by vibrating shaker were applied to verify the durability test. Comparing the experimental outcome and use the optimal electrospinning parameters to fabricate the piezoelectric fiber. The piezoelectric strain sensor is composed of thermoplastic polyurethane (TPU) and piezoelectric fiber bundle. A tensile test platform driven by a servo motor is applied to verify the sensor performance. Finally, the piezoelectric strain sensor is adhered on human body to measure the body movement. It is verified that the developed piezoelectric strain sensor can be used to measure the body movement on human skin for muscle monitoring, including Soleus muscle movement during running and jumping, concentric and eccentric movement of biceps and triceps, chest movement and detection of heart beat.

碩士
國立臺灣大學
工程科學及海洋工程學研究所
105
As increasing of aging population, all major developed countries are going into aging societies. With the technologies of smart wearable devices getting matured, the market demand of remote healthcare using smart wearable devices keeps increasing and hope to reduce overall medical expenses. The obstacles of smart wearable devices for health monitor are preciseness and power sources. Therefore, the objective of this study is to develop high-performance and flexible piezoelectric devices which can be accuracy tactile sensors or energy harvesters. In order to have higher strain, the plastic substrates are needed. The sintering process for piezoelectric (PZT) film is typically over 800 °C which is not suitable for plastic substrates. Therefore, the development of PZT films on low temp resist substrate is important. We proposed a newly designed process in transfer high-performance PZT film on plastic substrate by screen printing with transfer technique. The d31 mode energy harvester based on stainless steel substrate was fabricated. The PZT thickness is 21.4 μm. The device has 1.80 μW maximum output power and 4.42 Vp-p open-circuit output voltage under an excitation frequency of 62.9 Hz and 0.5 g excitation acceleration level. The d31 mode energy harvester based on PET substrate was fabricated by transferring technique. The PZT thickness is 17.3 μm. The device has 2.71 μW maximum output power and 7.19 Vp-p open-circuit output voltage under an excitation frequency of 70.4 Hz and 0.5 g excitation acceleration level. The banding test has the result of 3.15 Vp-p open-circuit output voltage under an excitation frequency of 1.15 Hz with 1 mm displacement. Moreover, the tactile sensor was made and measure with human pulses successfully. These results show the potential of smart wearable devices with accuracy tactile sensors by simply transferring techniques.

碩士
國立中興大學
機械工程學系所
101
The objective of this study is to study the mechanical properties of piezoelectric thin film on polyimide flexible substrate by tensile test. The first step is to fabricated and prepared the sample and the specimen, therefore PI+PZT and PI+SiO2 will be fabricated using low temperature sol-gel process to spin coated PZT to PI and SiO2 to PI at 3 different layers(thickness) respectively 3μm, 6μm and 9μm for PI+PZT and 3.6μm,7.2μm, 10.8μmfor PI+SiO2. During the sintering process raw PI will subject to the sintering temperature (1500 C for every sintering process, every layer) for 1, 2, 3 layers noted T1, T2, T3. Four type of sample was being needed for this experiment PI+PZT, PI+SiO2, raw PI at sintering Temperature and raw PI (PI without any treatment). Hand cutting will be used to prepare specimens using dog bone type specimen. Then a micro-force tensile testing machine (MTS Tytron 250 ) was used to test the specimens at different tensile speed 0.01mm/s, 0.04mm/s, 0.07mm/s and 0.1 mm/s. the offset method was used on the strain-stress curves to calculate the young’s modulus and the yield stress through Excel software trendline application. The experiment results showed that the tensile test can be used to successfully determine the young’s modulus and the yield stress of the piezoelectric thin film on flexible substrate, PI+SiO2 and raw PI. The yield stress and the young’s modulus show that the PZT SiO2 affect the mechanical behavior of the PI and affected it more with the increasing of the PZT or SiO2 film thickness by comparing with PZT it is shown that the SiO2 affect much more the PI mechanical behavior.It is shown that the effect of the sintering temperature (1500C) on the PI can be minimize because the PI glass temperature is more higher (4100C). Comparing the all strain-stress curves, young’s modulus and yield stress; it is shown that these devices are sensitive to the tensile speed.

In the thesis, motivated by the well-known universal approximation capability (input-output mapping) of the neural network (NNs), we have proposed adaptive NN controllers for a Rigid Link Flexible Joint (RLFJ) robot manipulator with unknown nonlinearities and piezoelectric actuator with unknown hysteresis, respectively. For a RLFJ robot manipulator, the dynamic model is decomposed into two different time scale models by using integral manifold method. The control torque consists of two terms: slow and fast terms for two time scale models. A composite NN-based control strategy is proposed for the position and velocity tracking of the manipulator. Two multilayer NNs are used to approximate two unknown nonlinear functions. These two NNs are tuned on-line without any off-line training. The stabilities of composite control system have been proved. The boundedness of NN weights and control signal of systems are guaranteed. Simulation results verify the developed control algorithms. The feedforward multilayer NN is also further investigated to approach the complicated nonlinear function in proposed hysteresis dynamics, which is described by Duhem model. An adaptive NN compensator is designed for unknown hysteresis in a piezoelectric actuator. A pre-inverse hysteresis function is well-structured and the effect of the actuator hysteresis is cancelled. The simulation results are also presented to show the effectiveness of the developed adaptive control scheme

碩士
國立臺灣科技大學
機械工程系
107
This study thoroughly analyzed to out-of-plane vibration of piezoelectric plate in several boundary conditions, based on theoretical analysis, finite element method (FEM) and experimental measurements. The Euler-Bernoulli beam theory is used to derive the vibration characteristics of the piezoelectric beam under different boundary conditions. The vibration mode of two-dimensional rectangular plate is analyzed by the beam function. Then the Rayleigh-Ritz method is used to determine the resonant frequency and vibration mode of the piezoelectric plate. The fully-clamped (CC), clamped-free (CF), fully-free (FF), spring-free (S+SrF) boundary conditions are determined theoretically, and the flexible support is discussed on the spring boundary both in the linear and the torsional springs, respectively. The finite element method is used to mainly verify on the correspondent resonant frequency of the thin plate under different linear stiffness and torsion stiffness. The experimental measurements are used to obtain the dynamic characteristics of piezoelectric materials. The full-filed optically technique, called as amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI), and the Laser Doppler Vibrometer (LDV) are used to obtain the vibration properties of piezoelectric specimen under CF and S+SrF boundary conditions. The theoretical analysis has good agreement with the experimental measurement and the finite element calculation. It showed that the flexible boundary condition used on piezoelectric plate has lower natural frequencies than the clamped-free boundary condition. The optimal design can be applied to variable stiffness piezoelectric energy harvesting system in approaching to the best efficiency in future.

碩士
國立高雄應用科技大學
機械工程系
105
For a piezoelectric motor design, the key point is how to design the flexible structure of the stator. Traditional mechanical analysis method is difficult to solve the problem of dynamic characteristic design of such flexible structure. So far, the solution is often based on the rule of thumb or trial and error method. However, it is extremely time-consuming and requires skilled designers for each design problem. In this thesis, a design method of topology optimization is proposed for the design of piezoelectric motors. It is carried out by using material distribution method, finite element analysis software ANSYS and Optimality Criteria. Firstly, the design area of the stator structure is set according to the different layout of the piezoelectric actuators in the design process. Then, the design parameters for the topology optimization are developed, and the element density distribution of the stator structure is calculated by the topology optimization process. The dimensions of the stator structure are obtained based on the element density distribution. In the design process, the objective is to design the stator with ideal tangential and normal vibration modes, where the natural frequencies of the two modes should be designed close to each other. Also, sufficient resonance amplitudes should be generated when the piezoelectric actuator is driven. Finally, a complete piezoelectric motor is formed by assembling the fixure, the slider, the pre-pressed spring mechanism and the stator, which is designed by the topology optimization mentioned above. After modal analysis and harmonic analysis of ANSYS, the results show that the first resonant frequency of the normal mode is 24.4 kHz and its resonance amplitude is 8.9μm/V, the first resonant frequency of the tangential mode is 24.2 kHz and its resonance amplitude is 3.7μm/V. The resonant frequencies of the two modes are different from each other by 0.2 kHz and the resonant amplitude of the normal mode is about 2.5 times of the tangential resonance amplitude, which satisfies the initial design requirements.

碩士
國立臺灣師範大學
機電工程學系
103
Herein this study reports the preparation of ZnO nanowires by using the hydrothermal method. Different lengths and width of ZnO nanowires array can be obtained by changing the sputtering parameter. We can obtain the longer and thick of ZnO nanowires with low surface roughness, but this result may bundle the nanowires. So we increase the surface roughness to avoid bundling the nanowires. PVDF was dissolved in acetone. The solution was dropped onto the substrate containing the ZnO nanostructures. Following spin-coating at 300, 500, 700, and 1000 rpm for 60 s, the film was poled at 160℃ for 30, 40, and 50 min. We can get the best output piezoelectric property from PVDF at 300 rpm and 50 min. To compare the pressure and bending sensing properties of the PVDF and PVDF/ZnO composite film. As the result, the PVDF/ZnO nanowires composite film exhibited the greatest signal in response, especially for a micro-loading sensing. Because of the 1D vertically ZnO nanowires, they generate an enhanced piezoelectric response to increase the sensitivity and lower the contact resistance at PVDF/Cu interface. In order o increase the output piezoelectric property, we increase the sensing area. The dipole moment under different sensing area determines the proportionally increased output voltage.

abstract: Technological advances in low power wearable electronics and energy optimization techniques make motion energy harvesting a viable energy source. However, it has not been widely adopted due to bulky energy harvester designs that are uncomfortable to wear. This work addresses this problem by analyzing the feasibility of powering low wearable power devices using piezoelectric energy generated at the human knee. We start with a novel mathematical model for estimating the power generated from human knee joint movements. This thesis’s major contribution is to analyze the feasibility of human motion energy harvesting and validating this analytical model using a commercially available piezoelectric module. To this end, we implemented an experimental setup that replicates a human knee. Then, we performed experiments at different excitation frequencies and amplitudes with two commercially available Macro Fiber Composite (MFC) modules. These experimental results are used to validate the analytical model and predict the energy harvested as a function of the number of steps taken in a day. The model estimates that 13μWcan be generated on an average while walking with a 4.8% modeling error. The obtained results show that piezoelectricity is indeed a viable approach for powering low-power wearable devices.
Dissertation/Thesis
Masters Thesis Electrical Engineering 2020

碩士
逢甲大學
自動控制工程所
90
This thesis proposes a novel neural network approach for the identification and control of a thin simply-supported plate. For the control purpose, the piezoelectric sensors and actuators are attached on the flexible structure. The motion behavior of a two-dimensional model of piezoelectric materials bounded to the surface of the flexible structure is analytically investigated. To consider practically the situation of motion for the plate, this thesis derives two different cases when piezoelectric element acts. One is distribution mode, and the other is bending mode. A novel linear differential inclusions (LDIs) is developed for a class of multilayer feedforward networks via the neural net-based identification architecture. With this technique, it is shown that the plant identified by the neural network can be represented as a linear time-invariant system. On the basis of the identified model, advanced linear control theory can be directly applied to design the stabilizing flexible structure controller.

碩士
中原大學
物理研究所
102
Abstract In this experiment, zinc oxide (ZnO) nanorods were grown on the flexible polyimide (PI) substrate with the hydrothermal method. Then poly(vinylidene fluoride) (PVDF) was spin-coated on the substrate to make it as a stable Piezoelectric composite sample. We analyzed its electrical and piezoelectric properties and discussed the influence from ZnO nanorods. Existence of the ZnO seed layer spin-coated on the sample induced the ZnO nanorods growth. Different reaction times and concentrations of the precursors affected the diameter and the length of the nanorods grown by the hydrothermal method. The size and orientation of ZnO nanorods tended to be distributed randomly with reaction time increasing. The structure grown with six hours showed preferred result. The concentration of the precursors also affected the diameter and the length of the ZnO nanorods. Energy Diffraction Spectroscopy (EDS) confirms that the composition of ZnO nanorods and PI substrate keep no change after annealing. The length and diameter of the layer thickness of PVDF were determined by Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM). The piezoelectric coefficient obtained in this experiment is between 2.23 and 9.73 µm/V. Compared with ZnO bulk material, the result shows that the piezoelectric coefficient increases with the material size decreasing. Finally, we discuss the relations among the structure of ZnO nanorods, the piezoelectric voltage and current density of the sample, and the precursor concentrations in ZnO growth.