Doctor of Philosophy, University of Akron, 2018, Mechanical Engineering

Acoustic/Elastic metamaterials have attracted increased attention in recent times. Metamaterials are defined as special materials that exhibit unusual properties not normally found in normal materials. These unusual properties are derived from the specially designed microstructures rather than the chemical composition of the material. Based on the concept of locally resonant metamaterials, these materials are applied in many applications such as impact wave attenuation, blast wave mitigation and wave control and manipulation due to their flexibility and tailoring properties for various needed applications. In this thesis, we present the development of a dissipative elastic metamaterial with multiple Maxwell-type resonators for dynamic load mitigation. Besides the wave attenuation of dynamic loads, we also investigate the asymmetric transmission of elastic waves which has recently been realized by linear structures. We design and propose different diatomic and triatomic elastic metamaterials to obtain large asymmetric elastic wave transmission in multiple low-frequency bands. All these frequency bands can be theoretically predicted to realize one-way wave propagation along different directions of transmission. All proposed models in this research are analytically investigated and numerically verified by both analytical lattice and continuum models. Also, the dynamic responses of the proposed models are explored and analyzed in time and frequency domains. The effect of damping on the proposed models is also investigated for more practical applications. Lastly, experimental verification is further conducted to observe wave asymmetric transmission bands and transient wave responses in time and frequency domains are also explored.

Committee: KWEK-TZE TAN PHD (Advisor); GRAHAM KELLY PHD (Committee Member); GREGORY MORSCHER PHD (Committee Member); PING YI PHD (Committee Member); MALENA ESPANOL PHD (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2013, Engineering and Applied Science: Electrical Engineering

Metamaterials, the artificially engineered left handed materials (LH), demonstrate unusual electromagnetic properties of simultaneous negative permittivity and permeability that are not available from the traditional right-handed (RH) materials. It has emerged as a new cutting edge technology involving physics, material science and engineering. The exceptional properties of metamaterials have attracted a lot of researchers and guided them to the development of a number of applications in various fields which would not have been possible with natural right-handed materials. The goal of this thesis is to design a metamaterial antenna, using Composite Right/left-Handed (CRLH) Transmission Line (TL), which can be used for various medical applications. The CRLH TL is the perfect representation of LH metamaterial which is thoroughly explained and verified by Agilent ADS momentum simulation. In this thesis, an 800 MHz metamaterial antenna is designed using CRLH TL. The various design configurations of the antenna are simulated in Agilent ADS momentum and their characteristics are analyzed to get the most efficient one. The antenna is very compact in size compared to the conventional microstrip rectangular patch antenna. It has been found that the balanced CRLH TL structure antenna characteristics exceed the performance of all other designs. It has the highest gain and radiated power and provides very high radiation efficiency. The metamaterial antennas are fabricated, tested, analyzed and their characteristics are compared with the simulation results.

Committee: Altan Ferendeci Ph.D. (Committee Chair); Marc Cahay Ph.D. (Committee Member); Peter Kosel Ph.D. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, Case Western Reserve University, 0, EMC - Mechanical Engineering

This dissertation introduces the nodal honeycomb lattice structure, inspired by conventional honeycomb and chiral structures, and designed for assembly compatibility, serving as a foundation for integrating additional system components. This structure facilitated the development of soft robots with shape-morphing skins and an untethered, soft-bodied robot. It addresses the gap in research on the practical applications of shape morphing in robotics by proposing a novel design approach that enhances the mobility and efficiency of soft robots through dynamic shape-changing capabilities. This allows robots to navigate through confined spaces more effectively than traditional designs. The work also details a metamaterial-based approach for developing an untethered, soft-bodied robot that overcomes the challenges of traditional fabrication methods through a semi-automated process involving 3D printing and discrete assembly. This process results in a customizable and scalable robot with multimodal and omnidirectional locomotion, addressing the need for fully integrated on-board systems for applications in diverse and unstructured environments. This dissertation demonstrates that the nodal honeycomb structure has the potential to serve as a foundational concept for application in various soft robotic designs.

Committee: Ozan Akkus (Committee Chair); Kathryn Daltorio (Committee Member); Umut Gurkan (Committee Member); Xiong Yu (Committee Member) Subjects: Design; Engineering; Mechanical Engineering; Mechanics; Robotics

Doctor of Philosophy, The Ohio State University, 2021, Physics

Time domain terahertz spectroscopy has allowed for a new way to analyze the properties of antiferromagnets. Since many materials have been explored using this technique, we took a different route for evaluating their properties. We evaluated how two different antiferromagnets (CaFe2O4 and TbMn2O5) interacted with metamaterials. CaFe2O4 was coupled to split ring resonators and TbMn2O5 was coupled to gammadion crosses. From the experiment performed on the CaFe2O4/split ring resonator sample, we did not find sufficient evidence indicating coupling between the sample and the metamaterial. For the TbMn2O5/gammadion sample, we observed an improvement in the efficiency of the electromagnon excitation compared to the bare sample. To understand why the expected anticrossing, an effect observed in coupled oscillator systems, was absent from either measurement, coupling effects between split ring resonators and a hypothetical antiferromagnet were analyzed more deeply utilizing numerical methods. From here we found that an anticrossing will occur when the spins in the crystal are parallel with the interface of the sample. This would allow for improved coupling between the magnetic moment of the split ring resonators and the antiferromagnet. From the data we were able to confirm the presence of an anticrossing. Following the metamaterial project, we began the development of an additional time domain terahertz technique, on chip terahertz, which allowed us to perform measurements on antiferromagnets that were not easily probed. This technique was applied to two different antiferromagnets, CaFe2O4 and MnPS3. For CaFe2O4, we observed a possible absorption in the spectrum that could be connected to on the magnon modes. For MnPS3, we detected three possible modes, one of which could be a low frequency magnon.

Committee: Rolando Valdes Aguilar (Advisor); Marc Bockrath (Committee Member); Ilya Gruzberg (Committee Member); Louis DiMauro (Committee Member) Subjects: Condensed Matter Physics; Physics

Doctor of Philosophy (Ph.D.), University of Dayton, 0, Electro-Optics

This work involves the analysis and design of metallo-dielectric structures for potential use as transmission filters. The Berreman matrix method, effective medium theory and anisotropic transfer matrix method are used to analyze propagation of electromagnetic/optical fields through these anisotropic metamaterial structures on various substrates. The design of such structures is performed using artificial neural networks. Both transverse electric and transverse magnetic polarizations are investigated. Effective medium theory along with the Berreman matrix method is used to analyze the optical properties such as reflection and transmission spectra through anisotropic media, which can be implemented using multilayer metallo-dielectric stacks of sub-wavelength dimensions. While multilayer anisotropic stacks of arbitrary thickness can be rigorously analyzed using 4x4 transfer matrix, in this work, a simplified 2x2 anisotropic transfer matrix technique is developed to analyze optical propagation through multilayer uniaxial stacks of arbitrary thicknesses. Optical transmission of a multilayer silver-zinc oxide stack deposited on a quartz substrate is modeled with this 2x2 anisotropic transfer matrix method along with effective medium theory and reconciled with experimental observations. Results indicate that this approach can be used for in situ assessment of the complex refractive indices of constituent metal and dielectric layers. Additionally, the anisotropic 2x2 transfer matrix method enables the possibility of modeling the transmission of the same metallo-dielectric structure deposited on an uniaxial electro-optic substrate. Simulation results predict that adjusting the bias field across the substrate results in an electrically tunable transmission filter. Following the analysis of transmission filters, an artificial neural network technique is used for the design of the optimum metallo-dielectric structure to achieve a given transmission spectrum. The uni (open full item for complete abstract)

Committee: Partha Banerjee (Advisor) Subjects: Electromagnetics; Nanoscience; Nanotechnology

Master of Science (M.S.), University of Dayton, 2017, Electro-Optics

Achieving high quality (Q)-factor resonant modes allows for drastic improvement of performance in many plasmonic structures. However, the excitation of high Q-factor resonances, especially multiple high q-factor resonances, has been a huge challenge in traditional metamaterials (MMs) due to ohmic and radiation losses. Here, we experimentally demonstrate simultaneous excitation of double Gaussian line shape resonances in a terahertz (THz) MM composed of an asymmetric 4-gap ring resonator. In a symmetric 4-gap ring resonator only the low Q-factor asymmetrically line shaped inductance-capacitive (LC) and dipole modes can be excited from an incident THz wave. By vertically displacing two adjacent arms a distance δ ≥ 40µm the fourfold symmetry of the planar MM breaks leading to two additional polarization dependent and frequency invariant higher Q-factor modes. The symmetry broken high Q-factor modes can be exploited for multi-band filters, slow light devices, and ultra-sensitive sensors. Therefore, we studied the performances of the symmetric and asymmetric MM devices as ultra-flexible biological sensors. An analyte of Bovine Serum Albumin (BSA) is applied to the surface of the MM causing each mode to uniquely red-shift linearly to the concentration of BSA. The results demonstrate the usefulness of a cost-effective THz planar MM-assisted biological sensor that could be used in food product quality, environmental monitoring, and global health care.

Committee: Jay Mathews (Advisor); Imad Agha (Committee Member); Andrew Sarangan (Committee Member); Thomas Searles (Committee Member) Subjects: Electrical Engineering; Optics; Physics

Master of Science in Engineering (MSEgr), Wright State University, 2014, Electrical Engineering

The design and characterization of metamaterials has emerged as a field of great interest in electromagnetics in recent years. The characterization has been accomplished primarily by means of fabrication, measurement, and parameter estimation. Previous work by Knisely and Havrilla [8] has shown that biaxial anisotropy can be created by machining air vias uniaxially into a homogeneous, isotropic material. This research project proposes a design method for manufactured biaxial materials. Full wave modeling and simulation is used for samples with varying via size, separation and pose to obtain the scattering parameters S11 and S21. To compare the simulated S-parameters to theoretical S-parameters of different dielectric values solved by mode matching, a cost function was created. The cost function is minimized using a constrained non-linear least squares optimization technique. When the global minimum of the cost function is found the material parameter for the values that optimized the function are estimated to be the values of the simulated material.

Committee: Michael Saville Ph.D., P.E. (Advisor); Doug Petkie Ph.D. (Committee Member); Yan Zhuang Ph.D. (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Master of Science (MS), Wright State University, 2007, Physics

The purpose of this project is to investigate the reflective properties of a left-handed metamaterial (LHM) through the use of a finite element analysis software called FEMLAB. In the 1960's, V. Veselago theorized that a material with negative permeability and negative permittivity has a negative index of refraction. In 2000, such a metamaterial was built and demonstrated at microwave frequencies. Previous work had focused on the transmission properties of the metamaterial. In our work, the reflected wave was examined for a LHM subject to an incident transverse electric wave. The different generalizations, first proposed by Veselago, of the Fresnel and Snell's equations for LHM's were rederived. We show that the reflectance does not distinguish between normal materials and metamaterials, and, through computational results, that FEMLAB can be used for LHM's.

Committee: Lok Lew Yan Voon (Advisor) Subjects:

MS, University of Cincinnati, 2011, Engineering and Applied Science: Electrical Engineering

The unusual properties exhibited by left-handed metamaterials have been of great interest to researchers, especially in the field of RF and Microwave communication. The property of backward-wave propagation has led to a number of applications which were not possible with natural right-handed materials. One of the most exciting applications of these left-handed metamaterials is the Zeroth Order Resonator (ZOR) wherein resonance is achieved even at the zeroth mode, which is not possible with the traditional right-handed materials. This has led to the design of Composite Right/Left-Handed (CRLH) ZOR antennas whose resonance frequency does not depend on the physical length of the resonator. In this thesis the theory behind the ZOR antennas is studied and their applicability for use as RFID tag antennas is explored. Three novel CRLH ZOR antenna configurations are proposed targeting the UHF RFID tag application. The antennas are simulated using Agilent ADS Momentum and the simulation results are compared with those of the traditional 2-cell and 4-cell CRLH ZOR antennas that have been previously designed. The novel antennas are also compared with a simple rectangular patch antenna to demonstrate the reduction in size achieved through the use of left-handed metamaterials. The novel antennas are also simulated with varying values of the substrate height, metal thickness, and dielectric loss tangent and the effect of these parameters on antenna performance is analyzed. The three novel antennas and a rectangular patch antenna are fabricated and the experimental results are presented. The novel antennas are found to be around 30 times smaller than the rectangular patch antenna radiating at the same frequency.

Committee: Altan Ferendeci PhD (Committee Chair); Joseph Thomas Boyd PhD (Committee Member); Carla Purdy PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2010, Electrical and Computer Engineering

Recent interest in new materials, including metamaterials and magneto-dielectrics, for RF applications provided strong impetus for measurement techniques to characterize associated permittivity, permeability, and loss factors. Traditional measurement techniques are not readily available to characterize these engineered composites. For example, conventional resonant cavity methods are known to be narrowband and require careful sample preparation. For metamaterials and magneto-dielectrics, broadband characterization is particularly necessary to observe their dispersive properties. Also, a challenge with new materials, such as layered composites, is the restriction in measurable shape, size and thickness. Often, small and irregularly shaped samples are available, making their characterization challenging. With these issues in mind, this dissertation is aimed at developing new characterization techniques for novel engineered composites. Specifically, four techniques are presented to characterize textured metamaterial volumetric structures, magneto-dielectric mixtures and films, and highly conductive metallo-dielectric films. One of the presented techniques is based on a Gaussian beam illumination. In this method, the Gaussian beam is used to illuminate the center of layered material samples to avoid diffraction from sample edges. In contrast to generating the Gaussian beam using bandwidth-limited lenses, the beam was reconstructed by scanning a probe over a virtual aperture much like the synthetic aperture radar process. This approach was successfully employed at X-band (8 to 12 GHz) for the characterization of slow-wave propagation in a layered metamaterial slab. However, the Gaussian beam method is not feasible at low frequencies as it requires a large sample aperture (> 1-wavelength in size). The second characterization method was, therefore, developed to measure smaller samples (< 0.25-wavelength) in lower frequencies (100 MHz to 4.8 GHz). More specifically, a str (open full item for complete abstract)

Committee: John L. Volakis (Committee Chair); Kubilay Sertel (Committee Co-Chair); Joel T. Johnson (Committee Member); Ronald M. Reano (Committee Member) Subjects: Electrical Engineering; Electromagnetism