A guided-wave THz System-on-Chip (TSoC) is emerging as an attractive alternative to the routine free-space THz systems to reduce physical bulk, propagation loss, pulse dispersion and cost of free-space THz systems. Recently, our research group succeeded in demonstrating a novel waveguided TSoC based on the coplanar stripline (CPS) transmission lines on a 1 µm-thin Silicon Nitride membrane. The novelty of this membrane-based platform was bonding the transmitter and receiver directly on the transmission line to eliminate the radiation loss by the routine THz optics. Besides, the delicate thin-membrane dramatically reduces the dielectric loss of the platform which results in low-loss and low-dispersion THz-bandwidth pulses. This Ph.D. dissertation presents the first end-to-end TSoC components that were designed and fabricated using the CPS transmission lines on 1 µm-thin Si3N4 membranes. These components are integrated into a TSoC by bending or connecting different impedance CPS transmission-line sections. We demonstrate four passive TSoC components: THz low-pass filter (TLPF), THz power divider (TPD), THz apodized Bragg grating (TABG) and THz branch-line coupler (TBLC). One of the most significant gains from this work is the assurance that more complex TSoCs can be designed and fabricated using this membrane-platform based on the strong agreement between simulation and experimental results. / Graduate / 2021-12-01

In recent years, research on development of chemical, biological and hazardous gas sensors for homeland security have attracted great deal of interest. Actuators possessing high sensitivity, easy fabrication techniques and excellent integration compatibility are in great demand. Towards this need, the development and characterization of improved sol-gel processing for in-house fabrication of highly sensitive and reliable Flexural Plate Wave (FPW) device was pursued This work focuses on an experimental design approach to improve texture and morphology of PZT thin film by systematically controlling the spin, pyrolysis and anneal cycles. The process alterations resulted in an 8-fold increase in the relative intensity of perovskite (111) phase, which consequently yielded a two fold improvement in remnant polarization and coercive field compared to industry recommended processes.

With increasing advancement in material science and computational power of current computers that allows us to analyze high dimensional systems, very light and large structures are being designed and built for aerospace applications. One example is a reflector of a space telescope that is made of membrane structures. These reflectors are light and foldable which makes the shipment easy and cheaper unlike traditional reflectors made of glass or other heavy materials. However, one of the disadvantages of membranes is that they are very sensitive to external changes, such as thermal load or maneuvering of the space telescope. These effects create vibrations that dramatically affect the performance of the reflector. To overcome vibrations in membranes, in this work, piezoelectric actuators are used to develop distributed controllers for membranes. These actuators generate bending effects to suppress the vibration. The actuators attached to a membrane are relatively thick which makes the system heterogeneous; thus, an analytical solution cannot be obtained to solve the partial differential equation of the system. Therefore, the Finite Element Model is applied to obtain an approximate solution for the membrane actuator system. Another difficulty that arises with very flexible large structures is the dimension of the discretized system. To obtain an accurate result, the system needs to be discretized using smaller segments which makes the dimension of the system very high. This issue will persist as long as the improving technology will allow increasingly complex and large systems to be designed and built. To deal with this difficulty, the analysis of the system and controller development to suppress the vibration are carried out using vector second order form as an alternative to vector first order form. In vector second order form, the number of equations that need to be solved are half of the number equations in vector first order form. Analyzing the system for control characteristics such as stability, controllability and observability is a key step that needs to be carried out before developing a controller. This analysis determines what kind of system is being modeled and the appropriate approach for controller development. Therefore, accuracy of the system analysis is very crucial. The results of the system analysis using vector second order form and vector first order form show the computational advantages of using vector second order form. Using similar concepts, LQR and LQG controllers, that are developed to suppress the vibration, are derived using vector second order form. To develop a controller using vector second order form, two different approaches are used. One is reducing the size of the Algebraic Riccati Equation to half by partitioning the solution matrix. The other approach is using the Hamiltonian method directly in vector second order form. Controllers are developed using both approaches and compared to each other. Some simple solutions for special cases are derived for vector second order form using the reduced Algebraic Riccati Equation. The advantages and drawbacks of both approaches are explained through examples. System analysis and controller applications are carried out for a square membrane system with four actuators. Two different systems with different actuator locations are analyzed. One system has the actuators at the corners of the membrane, the other has the actuators away from the corners. The structural and control effect of actuator locations are demonstrated with mode shapes and simulations. The results of the controller applications and the comparison of the vector first order form with the vector second order form demonstrate the efficacy of the controllers. / Ph. D.

O formato, posição e alinhamento corretos dos componentes oculares são definidos através de uma série de mudanças morfológicas complexas durante sua embriogênese. A retina se origina de células da vesícula óptica do tubo neural enquanto as células precursoras do cristalino surgem do ectoderma que reveste o ápice da vesícula óptica. Este ectoderma é delimitado molecularmente como pre-placoidal, sofre uma série de eventos morfogênicos durante o seu desenvolvimento inicial para formar o placóide do cristalino e, posteriormente, a vesícula do cristalino. O placóide do cristalino surge a partir do espessamento do ectoderma pre-placoidal. Posteriormente, o placóide invagina para formar a vesícula do cristalino. Durante a invaginação do placóide, as células da ectoderme que circundam o placóide (células periplacodais) também se movem para fechar a abertura do cristalino que invaginou e reconstruir o ectoderma da superfície. Aqui, nos concentramos em dois processos do desenvolvimento do olho. Nós investigamos o papel da matriz extracelular no espessamento do placóide do cristalino e a dinâmica da emissão de protrusões de membrana pelas células periplacodais durante a invaginação do placóide. A matriz extracelular desempenha papel relevante na morfogênese placodal. Por exemplo, a Fibronectina na matriz extracelular entre a vesícula óptica e o ectoderma pré-placoidal é necessária para a formação de placóide do cristalino. No entanto, a dinâmica da arquitetura de Fibronectina durante a formação do placóide é desconhecida. Assim, nosso primeiro objetivo aqui foi investigar a arquitetura da Fibronectina e da Laminina, dois importantes componentes da matriz extracelular, durante o espessamento do placóide do cristalino através de imagens confocais em 3D. Nossos dados sugerem que um padrão de Fibronectina e Laminina difuso e pontuado é restrito à região do placóide. Este padrão é mantido durante o espessamento e invaginação do placóide. Encontramos um padrão similar de Laminina na região do placóide de embrião de camundongo, sugerindo a conservação desta arquitetura neste contexto. Também demonstramos que a inibição mediada por Noggin (inibidor da sinalização de BMP), que interrompe o desenvolvimento do olho, afeta a organização da Fibronectina e da Laminina, sugerindo que a sinalização de BMP regula a organização da matriz extracelular durante o desenvolvimento do placóide do cristalino. Nosso segundo objetivo foi analisar a emissão de 5 protrusões celulares finas por células periplacodais correlacionando com o movimento de invaginação. Aqui, nós investigamos a dinâmica e composição do citoesqueleto dessas protrusões para entender sua função durante o desenvolvimento do olho. Observamos uma grande quantidade de protrusões em células periplacodais de embriões de galinha e de camundongo. Nossos resultados de quantificação com protrusões de embriões de galinha não mostraram correlação entre comprimento e direção de emissão ou com meia-vida. Nós também analisamos a diversidade na composição do citoesqueleto, uma vez que encontramos protrusões positivas para Cofilina e Tubulina. Estes dados sugerem uma população heterogênea de protrusões finas de membrana periplacodais. Finalmente, também identificamos essas protrusões em outras superfícies ectodérmicas de embriões de galinha e de camundongo, sugerindo que elas desempenham um papel no desenvolvimento de ectoderme superficial. / The correct shape, position and alignment of optic components are defined through a series of complex morphological changes during the embryogenesis of the eye. The retina originates from the neural tube´s optic vesicle while the lens precursor cells arise from the ectoderm that overlie the apex of the optic vesicle. This ectoderm is molecularly delimited as preplacodal and undergoes a series of morphogenic events during its initial development to form the lens placode and subsequently the lens vesicle. The lens placode arises from the thickening of the pre-placodal ectoderm. Subsequently, the placode invaginates to form the vesicle of the lens. During the invagination of the placode, the ectodermal cells that surround the placode (peri-placodal cells) also move to close the opening of the lens that invaginated and reconstruct the surface ectoderm. Here we focus on two processes of eye development. We investigated the role of the extracellular matrix in the lens placode thickening and the dynamics of the emission of membrane protrusions by the peri-placodal cells during the lens placode invagination. The extracellular matrix plays a relevant role in placodal morphogenesis. For example, Fibronectin in the extracellular matrix between the optic vesicle and the preplacodal ectoderm is required for the formation of lens placode. However, the dynamics of the Fibronectin architecture during placode formation is unknown. Thus, our first aim here was to investigate the architecture of Fibronectin and Laminin, two important components of the extracellular matrix, during thickening of lens placode through confocal 3D images. Our data suggest that both Fibronectin and Laminin present a diffuse and punctate pattern restricted to the placodal region. This pattern is maintained during thickening and invagination of the placode. We found a similar pattern of Laminin in the placodal region of the mouse embryo, suggesting the conservation of this architecture in this context. We also demonstrate that Noggin-mediated inhibition of BMP signalling, which disrupts the development of the eye, affects the organization of Fibronectin and Laminin, suggesting that BMP signalling regulates the organization of the extracellular matrix during the lens placode development. Our second objective was to analyse the emission of thin cellular protrusions by peri-placodal cells correlating with the lens invagination movement. Here we investigated the dynamics and 3 composition of the cytoskeleton of these protrusions to understand their function during the development of the eye. We observed a large number of protrusions in peri-satellite cells of chicken and mouse embryos. Our quantification results with chicken embryo protrusions showed no correlation between length and direction of emission or with half-life. We also analysed the diversity in the composition of the cytoskeleton, and we found protrusions positive for Cofilin and Tubulin. These data suggest a heterogeneous population of periplacodal protrusions. Finally, we have also identified these protrusions on other ectodermal surfaces of chicken and mouse embryos, suggesting that they play a role in the development of surface ectoderm.

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