The objective of the presented research is to develop a novel, ink-jet printed, chipless, passive, wireless sensor topology, which can radiate in a near isotropic pattern without interference from embedded devices, for use in dispersed sensor networks. This objective includes the development of a hardware based, uniquely identifiable, collision avoidance communication method, and an integrated sensor system that is easily integrated into the topology. Wireless sensor networks can be and are used in military, medical and industrial applications; and the demand for them is ever growing. However, current sensor networks have various trade-offs and limitations, including cost, number of distinguishable nodes, and ease of manufacturing. These trade-offs lead to unique sensors needing to be designed for each situation. To develop a widely used module, a topology must be developed that can meet as many demands as possible with fair tradeoffs. Many of the above proposed criteria for the topology are already integrated into RFID technology. Therefore, much of the research is the application and advancement of current RFID technology for the purpose of designing the topology. The research begins with the theory and design of conformal artificial magnetic conductors, which is used in the design of a near isotropic radiator and isolated core for device embedding. Then, novel fabrication techniques will be investigated and deployed in the fabrication of the topology. Next, a novel "smart skin" sensor is developed which is easily integrated into the desired fabrication technique. Finally, an anti-collision RFID circuit for on-tag placement, which is based on frequency-doubling transceivers, is designed, which can also be easily integrated into the final topology. This module is designed for use with a variety of different sensors. This versatility gives it ruggedness for use in many different environments. For proof of concept, this topology is fabricated and tested against current commercially sold tags. Through the design and testing of the radiator, circuitry, and embedded sensors, it is shown that this design is a suitable topology for use in many different environments and applications.

Carbon fiber reinforced polymer (CFRP) composites are known for their high stiffness-to-weight and high strength-to-weight ratios and hence are of great interest in several engineering fields such as aerospace, automotive and defense. However, despite their light weight, high stiffness and high strength, their application in these fields is limited due to their poor energy dissipation and vibration damping capabilities. This thesis presents a two-phase microlattice design to overcome this problem. To realize this design, a novel tape casting integrated multi-material stereolithography system is developed and mechanical properties of samples fabricated using this system are evaluated. The design incorporating a stiff phase (CFRP) and a high loss phase, exhibiting high stiffness as well as high damping, is studied via analytical and experimental approaches. To investigate its damping performance, mechanical properties at small-strain and large-strain regimes are measured through dynamic material analysis (DMA) and quasi-static cyclic compression tests respectively. It is seen that both intrinsic (small-strain) and structural (large-strain) damping in terms of a figure of merit (FOM), E1/3tanδ/ρ, can be enhanced by a small addition of a high loss phase in Reuss configuration. Moreover, it is seen that structural damping is improved at low relative densities due to the presence of elastic buckling during deformation. For design usefulness, tunability maps, displaying FOM in terms of design parameters, are developed by curve fitting of experimental measurements. The microlattice design is also evaluated quantitatively by comparing it with existing families of materials in a stiffness-loss map, which shows that the design is as stiff as commercial CFRP composites and as dissipative as elastomers. / Master of Science / Carbon fiber reinforced polymer (CFRP) composites are known for their lightweight, high stiffness and high strength and hence are of great interest in several engineering fields such as aerospace, automotive and defense. However, despite these advantages, their application in these fields is limited due to their poor energy dissipation and vibration damping capabilities. This thesis presents a novel cellular lattice design to overcome this problem. Recent growth in stereolithography (SLA) has enabled the fabrication of complex structures with high resolution. Using this capability of SLA additive manufacturing, a cellular design is developed to improve both the stiffness and damping performance of CFRP composites while reducing weight. Experiments are conducted to determine the stiffness and damping properties and small and large deformations. It is seen that the stiffness and damping properties can be increased through a two-material hybrid design, comprising of a high stiffness phase and a high damping phase, arranged in a specific pattern. The microlattice design is evaluated quantitatively by comparing it with the existing families of materials using an Ashby chart. The design shows a two order-of-magnitude increase in the stiffness-damping performance when compared to commercially available CFRP.

De par leur importante compressibilité et leur fréquence de résonance extrêmement basse, les bulles sont des objets physiques singuliers du point de vue de l'acoustique et de la mécanique des fluides. En utilisant la technique de la microfluidique afin de créer des assemblées de bulles bi-dimensionnelles, que nous excitons acoustiquement, nous étudions à la fois leur influence sur une onde sonore et sur le fluide présent à leur voisinage.Les bulles étant des résonateurs sub-longueur d'onde, nous montrons qu'une assemblée de micro-bulles va interagir avec une onde sonore de longueur d'onde bien plus importante que la taille des bulles individuelles. En proposant une méthode pour extraire la contribution des bulles au signal acoustique, nous montrons que leur résonance suit une loi légèrement modifiée par rapport à celle proposée par Minnaert pour des bulles sphériques.Nous avons également exploré le potentiel de ce système expérimental comme méta-matériau pour l'acoustique. Nous observons en effet une baisse de la transmission d'une onde sonore à travers ce matériau et ce, dans une gamme de fréquence située au-delà de la fréquence de résonance.Cette baisse de la transmission peut être ajustée à la fois en fréquence et en amplitude ce qui fait de ce système un méta-matériau adaptable dont les caractéristiques peuvent être facilement ajustées. / Because of the important compressibility of gas bubbles in water, inducing a very low resonance frequency, one can find interest in studying bubbles from an acoustic and a fluid mechanics point of view. Using microfluidics techniques in order to produce assemblies of acoustically driven bi-dimensional bubbles, we are studying their influence on both acoustic waves and the surrounding fluid.Bubbles being sub-wavelength resonators, we show that a micro-bubbles assembly interacts with acoustical waves which wavelengths that are substantially bigger than the bubbles size. Developing a way to extract bubbles contribution to the acoustic signal, we show that their resonance frequency follows a law slightly different from the one Minnaert had found for spherical bubbles. The impact of this medium on the acoustical wave has been studied and we show that a decrease in the acoustical transmission happens in a range of frequencies above the resonance. This decrease can be adjusted in amplitude and in frequency making our system an easily tunable metameterial.Because of the strong response of bubbles induced by acoustical waves, the bubbles surface oscillates with a great amplitude in the surrounding fluid. This oscillation, working together with a coupling present between the bubbles, can drive a strong steady streaming in the fluid. Systems of several bubbles are studied, and a theory is proposed in order to predict the flow they induce. The interaction between the streaming phenomenon and an external flow is also presented, showing that exclusion zones can be present under certain circumstances in these systems. These exclusion zones can be useful in micro-fluidics in order to trap particles or chemicals.

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Attenuation of low frequency turbofan engine noise has been a challenging task in an industry that requires low weight and tightly-packed solutions. Without innovative advancements, the technology currently used will not be able to keep up with the increasingly stringent requirements on aircraft noise reduction. A need exists for novel technologies that will pave the way for the future of quiet aircraft. This thesis investigates acoustic metamaterials and their ability to achieve superior transmission loss characteristics not found in traditional honeycomb liners. The acoustic metamaterials investigated are an array of Helmholtz resonators with and without coupled cavities periodically-spaced along a duct wall. Analytical, numerical, and experimental developments of these acoustic metamaterial systems are used herein to study the effects of this technology on the transmission loss. Particularly focusing on analytical modeling will aid in understanding the underlying physics that governs their interesting transmission loss behavior. A deeper understanding of the physics will be used to aid in future acoustic metamaterial liner design. A parameter study is performed to understand the effects of the geometry, spacing, and number of resonators, as well as resonator cavity coupling on performance. Increased broadband transmission loss, particularly in low frequencies, is achieved through intelligent manipulation of these parameters. Acoustic metamaterials are shown to have appealing noise cancellation characteristics that prove to be effective for aircraft engine liner applications. / Master of Science / Aircraft noise reduction is an ongoing challenge for the aerospace industry. Without innovative advancements, the next generation of aircraft will not be able to keep up with increasingly stringent noise regulations; novel acoustic technology is needed to pave the way for a future of quieter aircraft. This thesis investigates acoustic metamaterials and their ability to achieve superior noise reduction over traditional methods. Modeling techniques were developed, and experimental tests were conducted to quantitatively evaluate the effectiveness of a new acoustic metamaterial system. The acoustic metamaterial design explored herein was proven to reduce noise effectively and shows promise for a world of quieter aircraft.

<p dir="ltr">Vibration is ubiquitous in the modern world, making it a topic that cannot be avoided during design, manufacture, and maintenance. Systems, such as civil structures and suspension of cars, are normally designed to stay in the attenuation zone to avoid harsh vibrations. Designing and manufacturing systems with the desired natural frequency distribution is easy. However, it is much harder to maintain the frequency response since materials keep aging as time goes by. To counter the effect of aging and attenuate vibrations, this thesis designed a meta-material that is capable of reprogramming its natural frequency distribution by inserting various masses at different locations. This ability to specifically adjust the system's natural frequency distribution is what we define as "Digital Inertia Programming".</p><p dir="ltr">The model consists of 12 identical unit cells, with each unit cell comprising two types of springs. By determining whether to insert a mass into the unit cell at various locations, the model achieves its programmability to adjust its natural frequency distribution. A "Binary Representation" is used to label the patterns of mass inserted in the model. Each unit cell is represented by a binary bit and a total of 12 bits are used to indicate the presence of mass in each unit cell. In the thesis, we mainly discuss bilaterally symmetrical patterns to avoid unwanted twisting. For the 12 unit cells, we can obtain a total of 128 bilaterally symmetrical patterns, resulting in 896 independent natural frequencies for the model. The number of patterns and independent natural frequencies will increase exponentially with the increase of the number of unit cells in the model.</p><p dir="ltr">An ideal one-dimensional analytical metamaterial model is developed. Lagrange's method is used to determine the system's mass matrix and stiffness matrix directly from the kinetic energy and potential energy equations. The natural frequencies and mode shapes are then calculated from the eigenvalue equation. Based on free response analysis and sensitivity analysis, the model successfully showed great programmability on frequency distribution by varying the insert patterns, as well as changing the value of the variables in the model, such as the weight of the inserts, the weight of the top mass, the stiffness of the unit cell wall spring and the stiffness of the connecting spring. When continuously varying the parameter, the model's natural frequency distribution also changes continuously, giving a possibility to adjust the natural frequency distribution by carefully adjusting the weight of the mass inserted at each location. Lastly, a forced-response analysis is performed, and the amplitude of the model's frequency response is plotted. This provides a straightforward view of the changes in the band gaps and the overall stiffness of the model by altering the patterns with two inserts.</p><p dir="ltr">A two-dimensional model is developed based on the one-dimensional model. The model retains the same 12 unit cells setup as the one-dimensional model. Aiming to ensure stability, the rectangular-shaped unit cell is now configured as a combination of two triangles. Taylor expansion and small angle approximation are used to eliminate nonlinear terms and triangular function terms in the stiffness matrix respectively. The model again shows its programmability by adjusting the variables of the model. Since the results of asymmetrical patterns are bounded by the results of symmetrical patterns, including the asymmetrical patterns increases the model's precision. However, the symmetrical patterns already provide a good representation of the model. The rotational motion is added to the inserts in the model, which further increases the model's complexity. In the model, the mode shapes are characterized by the rotational motion of inserts and the horizontal motion of inserts, which correspond to a zero strain mode of the model. A linear regression model is trained based on 100 bilaterally symmetrical patterns to predict the second lowest natural frequencies of the two-dimensional model for both symmetrical and asymmetrical patterns. The success in the linear regression model indicates the potential for applying machine learning algorithms to the design of meta-materials in the future.</p>

abstract: To detect and resolve sub-wavelength features at optical frequencies, beyond the diffraction limit, requires sensors that interact with the electromagnetic near-field of those features. Most instruments operating in this modality scan a single detector element across the surface under inspection because the scattered signals from a multiplicity of such elements would end up interfering with each other. However, an alternative massively parallelized configuration, consisting of a remotely interrogating array of dipoles, capable of interrogating multiple adjacent areas of the surface at the same time, was proposed in 2002. In the present work a remotely interrogating slot antenna inside a 60nm silver slab is designed which increases the signal to noise ratio of the original system. The antenna is tuned to resonance at 600nm range by taking advantage of the plasmon resonance properties of the metal’s negative permittivity and judicious shaping of the slot element. Full-physics simulations show the capability of detecting an 8nm particle using red light illumination. The sensitivity to the λ/78 particle is attained by detecting the change induced on the antenna’s far field signature by the proximate particle, a change that is 15dB greater than the scattering signature of the particle by itself. To verify the capabilities of this technology in a readily accessible experimental environment, a radiofrequency scale model is designed using a meta-material to mimic the optical properties of silver in the 2GHz to 5GHz range. Various approaches to the replication of the metal’s behavior are explored in a trade-off between fidelity to the metal’s natural plasmon response, desired bandwidth of the demonstration, and ii manufacturability of the meta-material. The simulation and experimental results successfully verify the capability of the proposed near-field sensor in sub-wavelength detection and imaging not only as a proof of concept for optical frequencies but also as a potential imaging device for radio frequencies. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

This project is focused on computer modeling of so-called meta-materials, and on the exploitation of metamaterials in the design of electrically small antennas. For modeling, COMSOL Multiphysics 3.3 was used. Simulations were focused on impedance matching of antennas. Antennas with metamaterials were compared with corresponding conventional antennas without metamaterial layers. The project does not investigate the creation of metamaterials; the project concentrates on their influence on crucial parameters of antennas. Next step this project is focused on optimalization this structure in program Matlab version R2009b. We used optimalization method PSO (swarms of particles) and results are comparing whit results calculating in COMSOL program.