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Yes / In order to improve the frequency-dependent dielectric properties of the immiscible polymeric blends which were melt-compounded by composing poly (vinylidene fluoride) (PVDF) and low density polyethylene (LDPE), the layer multiplication and the solid phase orientation technologies were respectively adopted as two effective strategies to optimize the dispersion state and the orientation of internal microstructure, aiming at reducing physical porosity and improving the barrier performance as well as crystal phase of the polymer extrudates. Results comparison showed the dielectric properties were greatly dependent on the crystal type and the physical porosity density which were also emphasized as the interfacial effect in the previous work [ref. 29: Lin X et al, J Appl Polym Sci 2015; 132(36), 42507]. It was found that the multilayer-structure manipulation could substantially improve the dispersion state between the two immiscible components, enhance the mechanical performance and reduce the internal defects and increase the dielectric constant while keeping the dielectric loss stable. By uniaxial stretching the sample sheets at a rubber state temperature of ca. 10-20˚C below the melting point, crystal transformation was induced by increasing molecular chains orientation degree which was also contributed to the enhancement of the dielectric properties. These techniques implied the potential as a promising way for inducing functional structures of polymeric blends.

Three-dimensional (3D) polymer structures are very attractive because the extra structural dimension can provide denser integration and superior performance to accomplish complex tasks. Successful fabrication of 3D multilayer microstructures in thermoplastic polymers using optimized nanoimprint lithography techniques such as layer-transfer and transfer-bonding methods are developed in this dissertation work. The capability and flexibility of the techniques developed here are expected to have deep impact on the applications of soft materials such as polymers including functional polymers in micro- and nanofabricated devices and systems. Although NIL technique is developing rapidly in recent years, there are still issues that need to be addressed for broader adoption of the nanoimprint technique. One of the problems is the residual layer that remains in the polymer pattern after nanoimprint. The conventional approach, oxygen reactive-ion-etching (RIE) process, to remove the residual layers, increases the cost and lowers the overall throughput of the nanoimprint process. More severely, it can degrade or even damage the functional polymers. In order to overcome these problems, new residual layer removal techniques need to be developed. In this dissertation, two methods are newly developed, which do not negatively affect the chemistry of the polymer materials. The techniques are suitable for all thermoplastic polymers, particularly functional polymers. Another advantage of nanoimprint is its ability to directly create functional polymers structures. This is because thermal nanoimprint only needs temperature and pressure for pattern replication, which both are benign to functional polymers. This feature combined with newly developed techniques such as transfer-bonding and residue removal techniques opens up the possibilities in nondestructive functional polymers patterning at the micro- and nanoscale for novel applications in electronics, optoelectronics, photonics and bioengineering. Finally, several applications of 3D multilayer structures fabricated by the techniques developed in this dissertation are demonstrated. The first application is a multilayer metal-dielectric-metal structure with embedded microfluidic channels. This structure can be used as an on-chip tunable filter for integrated microfluidic applications. The second application is a multilayer microfluidic channels in which each layer has a different channel size. This device can be used for particle separation and filtration based on lateral fluid flow.

The incorporation of active piezoelectric elements and fluidic components into micro-electromechanical systems (MEMS) is of great interest for the development of sensors, actuators, and integrated systems used in microfluidics. Low temperature cofired ceramics (LTCC), widely used as electronic packaging materials, offer the possibility of manufacturing highly integrated microfluidic systems with complex 3-D features and various co-firable functional materials in a multilayer module. It would be desirable to integrate high performance lead zirconate titanate (PZT) based ceramics into LTCC-based MEMS using modern thick film and 3-D packaging technologies. The challenges for fabricating functional LTCC/PZT devices are: 1) formulating piezoelectric compositions which have similar sintering conditions to LTCC materials; 2) reducing elemental inter-diffusion between the LTCC package and PZT materials in co-firing process; and 3) developing active piezoelectric layers with desirable electric properties. The goal of present work was to develop low temperature fired PZT-based materials and compatible processing methods which enable integration of piezoelectric elements with LTCC materials and production of high performance integrated multilayer devices for microfluidics. First, the low temperature sintering behavior of piezoelectric ceramics in the solid solution of Pb(Zr0.53,Ti0.47)O3-Sr(K0.25, Nb0.75)O3 (PZT-SKN) with sintering aids has been investigated. 1 wt% LiBiO2 + 1 wt% CuO fluxed PZT-SKN ceramics sintered at 900oC for 1 h exhibited desirable piezoelectric and dielectric properties with a reduction of sintering temperature by 350oC. Next, the fluxed PZT-SKN tapes were successfully laminated and co-fired with LTCC materials to build the hybrid multilayer structures. HL2000/PZT-SKN multilayer ceramics co-fired at 900oC for 0.5 h exhibited the optimal properties with high field d33 piezoelectric coefficient of 356 pm/V. A potential application of the developed LTCC/PZT-SKN multilayer ceramics as a microbalance was demonstrated. The final research focus was the fabrication of an HL2000/PZT-SKN multilayer piezoelectric micropump and the characterization of pumping performance. The measured maximum flow rate and backpressure were 450 μl/min and 1.4 kPa respectively. Use of different microchannel geometries has been studied to improve the pumping performance. It is believed that the high performance multilayer piezoelectric devices implemented in this work will enable the development of highly integrated LTCC-based microfluidic systems for many future applications.

No description available.

<p>Resonant-cavity-enhanced (RCE) photodetectors have recently attracted attention due to their wavelength selectivity and high efficiency in comparison to conventional photodetectors. The goal of this ongoing research initiative is to develop a Si-based RCE infrared photodetector using inductively coupled plasma chemical vapor deposition (ICP-CVD) as the primary fabrication method. At the current stage of the project, wavelength-selective optical structures have been successfully fabricated using Si/SiO₂ layer pairs. These structures demonstrate sharp transmission peaks at their intended wavelength, making them potentially useful for efficient photodetection. The next phase of the photodetector development process involves using ion implantation to introduce dopants and create the bias.The project also explores the temperature sensing capability of the resonant-cavity structures. The temperature sensitivity tests indicate that the specific type of structure fabricated in this project may be relevant for fiber-optic temperature sensing applications. Additional testing is required to evaluate the performance characteristics of such structures as Fabry-Perot sensors capable of wavelength-encoded temperature measurement.</p> / Master of Applied Science (MASc)

Les chaussées subissent des sollicitations liées au trafic et au climat conduisant à leur dégradation, par fissuration notamment. Il est nécessaire dans le contexte actuel de pouvoir modéliser le comportement de ces structures multicouches endommagées afin de prévoir leur durée de vie résiduelle ou dimensionner des solutions de renforcement. L’objectif de la thèse est ainsi de proposer un outil de calcul dédié à l'analyse 3D des chaussées fissurées ou comportant des discontinuités. L’approche retenue repose sur la modélisation simplifiée d’une chaussée par un empilement de plaques du Modèle Multi-particulaire des Matériaux Multicouches à 5n équations d’équilibre (M4-5n). Un outil de calcul rapide de référence de chaussées 2D fissurées et une méthode de résolution générale du M4-5n par Eléments Finis mixtes sont développés. Le point de départ de la méthode de résolution est l’écriture, pour le M4-5n, du principe variationnel basé sur le théorème de l'énergie complémentaire où la condition de contraintes statiquement admissibles est assurée à partir de multiplicateurs de Lagrange. La discrétisation des efforts généralisés utilise des espaces d’interpolation permettant le bon conditionnement du système d’équations algébriques à résoudre et garantissant la stabilité de la solution. La méthode est implémentée dans FreeFem++. Elle ramène le problème 3D initial à une modélisation EF 2D et conduit à des valeurs finies des efforts généralisés au niveau des fissures ou décollement d’interface. L’outil de calcul final ainsi développé est validé et appliqué à l’étude de la réponse d’une structure fissurée,représentative d’une chaussée testée en vraie grandeur sur le site de l’IFSTTAR. / Pavements are multilayer structures which undergo cracking distress due to traffic and climatic factors. It is important nowadays to be able to model the mechanical response of such damaged pavements in order to assess their residual lifetime or to design reinforcement solutions. In this context, the present thesis aims at developing a numerical tool dedicated to the analysis of pavements incorporating cracks or discontinuities. In the developed approach, the pavement structure is modeled as a stacking of “plate” elements of typeM4-5n (Multi-Particle Models of Multilayer Materials) which considers 5n equilibrium equations. A reference quick 2D calculation tool for cracked pavements and a general solving of M4-5n by the mixed Finite Element (FE) method was developed. The starting point for this method is the derivation for M4-5n of the variational principle based on the complementary energy theorem whose condition of statically admissible stress is taken into account using Lagrange multipliers. Discretization of the generalized stresses involves interpolation spaces, proposed to avoid ill-conditioned system of algebraic equations after discretization and to insure stability of the solution. The developed method is implemented in a FreeFem++ script. In this method, the initial 3D problem can be handled through FE simulations in 2D and finite values of the generalized stresses are obtained at crack and interlayer debonding locations. The developed numerical tool was validated and applied to the study of the mechanical response of a structure with cracks representative of a pavement tested underfull-scale conditions during an accelerated fatigue test performed at IFSTTAR.

The doctoral thesis deals with the structure and properties of the polycrystalline silicon layers deposited on the silicon wafers backside. The wafers are further used for production of semiconductor devices. This work is focused on detailed description of the layers structure and study of the gettering properties and residual stress of the layers. The main goal of this work is to develop two novel technologies. The first one leads to improvement of the temperature stability of the gettering properties of the layers, and the second one solves the deposition of the layers with pre-determined residual stress. This doctoral thesis was created with the support of the company ON Semiconductor Czech Republic, Rožnov pod Radhoštěm.

Made available in DSpace on 2014-12-17T14:56:05Z (GMT). No. of bitstreams: 1 KesiaCS.pdf: 532004 bytes, checksum: e5e91d569fd4794eb815f8bbbd565c37 (MD5) Previous issue date: 2005-12-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Recently the planar antennas have been studied due to their characteristics as well as the advantages that they offers when compared with another types of antennas. In the mobile communications area, the need for this kind of antennas have became each time bigger due to the intense increase of the mobile communications that needs of antennas which operate in multifrequency and wide bandwidth. The microstrip antennas presents narrow bandwidth due the loss in the dielectric generated by radiation. Another limitation is the radiation pattern degradation due the generation of surface waves in the substrate. In this work some used techniques to minimize the disadvantages (previously mentioned) of the use of microstrip antennas are presented, those are: substrates with PBG material - Photonic Bandgap, multilayer antennas and with stacked patches. The developed analysis in this work used the TTL - Transverse Transmission Line method in the domain of Fourier transform, that uses a component of propagation in the y direction (transverse to the direction real of propagation z), treating the general equations of electric and magnetic field as functions of y and y . This work has as objective the application of the TTL method to microstrip structures with single and multilayers of rectangular and triangular patches, to obtaining the resonance frequency and radiation pattern of each structure. This method is applied for the treatment of the fields in stacked structures. The Homogenization theory will be applied to obtaining the effective permittivity for s and p polarizations of the substrate composed of PBG material. Numerical results for the triangular and rectangular antennas with single layer, multilayers resonators with triangular and rectangular patches are presented (in photonic and isotropic substrates). Conclusions and suggestions for continuity of this work are presented / Recentemente as antenas planares t?m despertado interesses devido ?s suas caracter?sticas assim como pelas vantagens que oferecem quando comparadas com os demais tipos de antenas. Na ?rea de comunica??es m?veis a necessidade de antenas desse tipo tem se tornado cada vez maior devido ao intenso crescimento das comunica??es m?veis que necessitam de antenas que operem em multifreq??ncia e em banda larga. As antenas de microfita apresentam largura de banda estreita devido ?s perdas no diel?trico geradas pela irradia??o. Outra limita??o ? a degrada??o do diagrama de irradia??o devido ? gera??o de ondas de superf?cie no substrato. Neste trabalho s?o apresentadas algumas t?cnicas usadas para tentar minimizar as desvantagens (citadas acima) do uso de antenas de microfita, sendo elas: substratos com material PBG &#150; Photonic Bandgap, antenas em multicamadas e com patches empilhados. As an?lises desenvolvidas neste trabalho foram realizadas com a utiliza??o do m?todo LTT &#150; Linha de Transmiss?o Transversa no dom?nio da transformada de Fourier que utiliza uma componente de propaga??o na dire??o y (transversa ? dire??o real de propaga??o z), tratando assim as equa??es gerais dos campos el?tricos e magn?ticos em fun??es de y e y . Este trabalho tem como objetivo a aplica??o do m?todo LTT ?s estruturas de microfita com uma e multicamadas de patch retangular e triangular, para a obten??o da freq??ncia de resson?ncia e diagrama de irradia??o de cada estrutura. Este m?todo ? aplicado para o tratamento dos campos em estruturas planares empilhadas. A teoria da Homogeneiza??o ser? aplicada para a obten??o da permissividade efetiva para as polariza??es s e p dos substratos compostos de material PBG - Photonic Bandgap. Resultados num?ricos para as antenas triangulares e retangulares com uma camada e ressoadores com multicamadas de patch retangular e triangular s?o apresentados (em substratos isotr?picos e fot?nicos). S?o apresentadas conclus?es e sugest?es para a continuidade deste trabalho