A negative index material (NIM), which possesses simultaneously negative permittivity and permeability, is an emerging material that has caught many researchers attention after it was first demonstrated in 2001. It has been shown that electromagnetic waves propagating in NIMs have some remarkable properties such as negative phase velocities and negative refraction and hold enormous promise for applications in imaging and optical communications. This dissertation is centered on investigating the unique aspects of the radiative properties of NIMs. Photon tunneling, which relies on evanescent waves to transfer radiative energy, has important applications in thin-film structures, microscale thermophotovoltaic devices, and scanning thermal microscopes. With multilayer thin-film structures, photon tunneling is shown to be greatly enhanced using NIM layers. The enhancement is attributed to the excitation of surface or bulk polaritons, and depends on the thicknesses of the NIM layers according to the phase matching condition. A new coherent thermal emission source is proposed by pairing a negative permittivity (but positive permeability) layer with a negative permeability (but positive permittivity) layer. The merits of such a coherent thermal emission source are that coherent thermal emission occurs for both s- and p-polarizations, without use of grating structures. Zero power reflectance from an NIM for both polarizations indicates the existence of the Brewster angles for both polarizations under certain conditions. The criteria for the Brewster angle are determined analytically and presented in a regime map. The findings on the unique radiative properties of NIMs may help develop advanced energy conversion devices. Motivated by the recent advancement in scanning probe microscopy, the last part of this dissertation focuses on prediction of the radiation heat transfer between two closely spaced semi-infinite media. The objective is to investigate the dopant concentration of silicon on the near-field radiation heat transfer. It is found that the radiative energy flux can be significantly augmented by using heavily doped silicon for the two media separated at nanometric distances. Large enhancement of radiation heat transfer at the nanoscale may have an impact on the development of near-field thermal probing and nanomanufacturing techniques.

Vibration energy harvesters, or energy scavengers, recover mechanical energy from their surrounding environment and convert it into useable electricity as sustainable self-sufficient power sources to drive micro-to milli-Watt scale power electronics in small, autonomous, wireless devices and sensors. Using semiconducting, organic piezoelectric nanomaterials are attractive in low-cost, high resistance to fatigue, and environmentally friendly applications. Significantly, the deposition processes of sputtering ZnO (zinc oxide) thin films with high c-axis preferred orientation and electrospun PVDF (polyvinylidene fluoride) nanofibers with high piezoelectric £]-phase crystallisation are controlled at room temperature. Thus they don¡¦t have the necessity of post-annealed and electrical repoling process to obtain an excellent piezoelectricity, and are suitable for all flexible substrates such as PET (polyethylene terephthalate) and PI (polyimide). These works are divided into two parts. Part 1: Flexible piezoelectric harvesters based on ZnO thin films for self-powering and broad bandwidth applications. A new design of Al (aluminum)/PET-based flexible energy harvester was proposed. It consists of flexible Al/PET conductive substrate, piezoelectric ZnO thin film, selectively deposited UV (ultraviolet)-curable resin lump structures and Cu (copper) foil electrode. The design and simulation of a piezoelectric cantilever plate was described by using commercial software ANSYS FEA (finite element analysis) to determine the optimum thickness of PET substrate, internal stress distribution, operation frequency and electric potential. With the optimum thickness predicted by developed accurate analytical formula analysis, the one-way mechanical strain that is efficient to enhance the induced electric potential can be controlled within the piezoelectric ZnO layer. In addition, the relationship among the model solution of piezoelectric cantilever plate equation, vibration induced electric potential and electric power was realized. ZnO thin film of high (002) c-axis preferred orientation with an excellent piezoelectricity was deposited on the Al/PET by RF (radio-frequency) magnetron sputtering in room temperature. Al was sputtered on the PET substrate as the bottom electrode because of its low sheet resistance, superior adhesion with PET, and lattice constants matching with ZnO thin film. The selectively deposited UV-curable resin lump structures as proof mass were directly constructed on flexible piezoelectric plate using electrospinning with a stereolithography technique. One individual harvester achieves a maximum OCV (open-circuit voltage) up to 4V with power density of 1.247 £gW/cm2. This self-powered storage system can drive the warning signal of the LED (light emitting diode) module in both resonant and non-resonant conditions. We also succeeded in accomplishing a broad bandwidth harvesting system with operating frequency range within 100 Hz to 400 Hz to enhance powering efficiency. This system comprises four units of individual ZnO piezoelectric harvester in the form of a cantilever structure connected in parallel, and rectifying circuit with storage module. In addition, a modified design of a flexible piezoelectric energy-harvesting system with a serial bimorph of ZnO piezoelectric thin film was presented to enhance significantly higher power generation. This high-output system was examined at 15 Hz. The maximum DC (direct current) voltage output voltage with loading was 3.18 V, and the maximum DC power remained at 2.89 £gW/cm2. Furthermore, in order to examine the deformation between interfaces and the adhesion mechanism of multi-layer flexible electronics composites (e.g., ITO (indium tin oxide)/PET, Al/PET, ZnO/ITO/PET, and ZnO/Al/PET), nanoscratching and nano-indention testing (nanoindenter XP system) were conducted to analyze the adhesion before and after the vibration test. The plastic deformation between the ductile Al film and PET substrate is observed using SEM (scanning electron microscopy). Delamination between the ZnO and Al/PET substrate was not observed. This indicates that Al film provides excellent adhesion between the ZnO thin film and PET substrate. Part 2: Pre-strained piezoelectric PVDF nanofiber array fabricated by near-field electrospining on cylindrical process for flexible energy conversion. In various methodologies of energy harvesting from ambient sources, one-dimensional nanoharvesters have been gaining more attention recently. However, these nanofibers fabricated by micro-forming technologies may not easily control their structural diameter and length. This study originally presented the HCNFES (hollow cylindrical near-field electrospining) process to fabricate permanent piezoelectricity of PVDF piezoelectric nanofibers. Under high in-situ electric poling and strong mechanical stretching effect during HCNFES process, large PVDF nanofiber array with high piezoelectric £]-phase crystallisation was demonstrated. These pre-strained piezoelectric PVDF nanofibers fabricated by HCNFES with high process flexibility at low cost, availability in ultra-long lengths, various thicknesses and shapes can be applied at power scavenge, sensing and actuation. Firstly, PVDF nanofibers lay on a PET substrate, silver paste was applied at both ends of fibers to fix their two ends tightly on a Cu foil electrode pair. The entire structure was packaged inside a thin flexible polymer to maintain its physical stability. Repeatedly stretching and releasing the nanoharvester (NH 1) with a strain of 0.05% at 5 Hz vibration created a maximum peak voltage and current of -50 mV and -10 nA in forward connection, respectively. Secondly, a total of 44 parallel nanofibers have been fabricated and transferred onto an IDT (interdigital) electrode with 64 electrode pairs as a nanohavester (NH 2) to amplify current outputs under repeated mechanical vibration and impact tests. Under a repeated maximum strain of 0.14% at 6 Hz vibration, a peak current of 39 nA and peak voltage of 20.2 mV have been measured. Impact testing at 15 Hz, peak current of 130 nA has been collected with a voltage of 24.4 mV. Finally, the single PVDF fiber as nanoharvester (NH 3) with a strain of 0.05-0.1% at 5 Hz vibration created a maximum peak voltage and current of -45 mV and -3.9 nA, respectively. The maximum power remained at 18.45 pW/cm2 with a load resistor of 6.8 M£[. Based on the mechanism of converes piezoelectric effect, ANSYS software with coupled field analysis was used to realize piezoelectric actuation behavior of the PVDF fibers. From the observation of actuation property, a fixed-fixed single nanofiber was tested under different DC voltage supply. Comparing the polarized fiber with non-polarized fibers, the measurement of the center displacements as a function of electric field was conducted and characterized.

The sediment resuspension and turbidity created during dredging operations is both an economical and environmental issue. The movement of sediment plumes created from dredging operations has been predicted with numerical modeling, however, these far-field models need a “source term” or near-field model as input. Although data from field tests have been used to create near-field models that predict the amount of material suspended in the water column, these results are skewed due to limitations such as non-uniform sediment distributions, water currents, and water quality issues. Laboratory investigations have obtained data for turbidity during dredging operations, but these results do not take advantage of the most contemporary testing methods. The purpose of this dissertation is to provide an estimation of turbidity created during a cutter suction dredging operation. This estimation was facilited by the development of resuspension measurement and data acquisition techniques in a laboratory setting. Near-field turbidity measurements around the cutter head were measured in the Haynes Coastal Engineering Laboratory at Texas A&M University. The laboratory contains a dredge/tow tank that is ideal for conducting dredging research. A dredge carriage is located in the dredge/tow tank and is composed of a carriage, cradle, and ladder. Acoustic Doppler Velocimetry (ADV) and Optical Backscatter Sensor (OBS) measurements were taken at specific points around the cutter head. The variables of suction flow rate, cutter speed, and the thickness of cut were investigated to understand their specific effect on turbidity generation and turbulence production around the cutter head. A near-field advection diffusion model was created to predict resuspension of sediment from a cutter suction dredge. The model incorporates the laboratory data to determine the velocity field as well as the turbulent diffusion. The model is validated with laboratory testing as well as field data. Conclusions from this research demonstrate undercutting consistently produced larger point specific turbidity maximum than overcutting in the laboratory testing. An increase in suction flow rate was shown to increase production and decrease turbidity around the cutter head. In general, an increase in cutter speed led to an increase in turbidity. The thickness of cut produced less resuspension for a full cut versus a partial cut. Data for a “shallow cut” also produced less turbidity generation than partial cuts. The numerical model was compared to all laboratory testing cases as well as the Calumet Harbor and New Bedford cutter resuspension data and produced suitable MRA values for all tests. The numerical model produced higher point specific regions of turbidity for undercutting but produced larger mean values of turbidity for overcutting.

Though the Aerospace industry is moving towards small satellites and smaller sensor technologies, sensors used for close-proximity operations are generally cost (and often size and power) prohibitive for University-class satellites. Given the need for low-cost, low-mass solutions for close-proximity relative navigation sensors, this research analyzed the expected errors due to near-field effects using a coarse sun sensor as part of a 6-degree-of-freedom (6-dof) solution. To characterize these near-field effects, a test bed (Characterization Test Apparatus or CTA) was proposed, its design presented, and the design stage uncertainty analysis of the CTA performed. A candidate coarse sun sensor (NorthStarTM) was chosen for testing, and a mathematical model of the sensor’s functionality was derived. Using a Gaussian Least Squares Differential Correction (GLSDC) algorithm, the model parameters were estimated and a comparison between simulated NorthStarTM measurements and model estimates was performed. Results indicate the CTA is capable of resolving the near-field errors. Additionally, this research found no apparent show stoppers for using coarse sun sensors for 6-dof solutions.

The damaging effects of strong ground motions on highway bridges have revealed the limitations of conventional design methods and emphasized the need for innovative design concepts. Although seismic isolation systems have been proven to be an effective method of improving the response of bridges during earthquakes, the performance of base-isolated structures during near-field earthquakes has been questioned in recent years. Near-field earthquakes are characterized by long period and large- velocity pulses. They amplify seismic response of the isolation system since the period of these pulses usually coincides with the period of the isolated structures. This study explores the feasibility and effectiveness of shape memory alloy (SMA)-based isolation systems in order to mitigate the response of bridge structures against near-field ground motions. SMAs have several unique properties that can be exploited in seismic control applications. In this work, uniaxial tensile tests are conducted first to evaluate the degree to which the behavior of SMAs is affected by variations in loading rate and temperature. Then, a neuro-fuzzy model is developed to simulate the superelastic behavior of SMAs. The model is capable of capturing rate- and temperature-dependent material response while it remains simple enough to carry out numerical simulations. Next, parametric studies are conducted to investigate the effectiveness of two SMA-based isolation systems, namely superelastic-friction base isolator (S-FBI) system and SMA/rubber-based (SRB) isolation system. The S-FBI system combines superelastic SMAs with a flat steel-Teflon bearing, whereas the SRB isolation system combines SMAs with a laminated rubber bearing rather than a sliding bearing. Upon evaluating the optimum design parameters for both SMA-based isolation systems, nonlinear time history analyzes with energy balance assessment are conducted to compare their performances. The results show that the S-FBI system has more favorable properties than the SRB isolation system. Next, the performance of the S-FBI systems is compared with that of traditional isolation systems used in practice. In addition, the effect of outside temperature on the seismic response of the S-FBI system is assessed. It is revealed that the S-FBI system can successfully reduce the response of bridges against near-field earthquakes and has excellent re-centering ability.

Non-radiative wireless power transfer using the coupled mode resonance phenomenon has been widely reported in the literature. However, the distance over which such phenomenon exists is very short when measured in terms of wavelength. In this dissertation, how efficient wireless power transfer can be realized in the radiating near-field region beyond the coupled mode resonance region is investigated. First, electrically small folded cylindrical helix (FCH) dipole antennas are designed to achieve efficient near-field power transfer. Measurements show that a 40% power transfer efficiency (PTE) can be realized at the distance of 0.25λ between two antennas in the co-linear configuration. These values come very close to the theoretical upper bound derived based on the spherical mode theory. The results also highlight the importance of antenna radiation efficiency and impedance matching in achieving efficient wireless power transfer. Second, antenna diversity is explored to further extend the range or efficiency of the power transfer. For transmitter diversity, it is found that a stable PTE region can be created when multiple transmitters are employed at sufficiently close spacing. For receiver diversity, it is found that the overall PTE can be improved as the number of the receivers is increased. Third, small directive antennas are investigated as a means of enhancing near-field wireless power transfer. Small directive antennas based on the FCH design are also implemented to enhance the PTE. It is shown that the far-field realized gain is a good surrogate for designing small directive antennas for near-field power transfer. Fourth, to examine the effects of surrounding environments on near-field coupling, an upper bound for near-field wireless power transfer is derived when a transmitter and a received are separated by a spherical material shell. The derived PTE bounds are verified using full-wave electromagnetic simulation and show good agreement for both TM mode and TE mode radiators. Using the derived theory, lossy dielectric material effects on wireless power transfer are studied. Power transfer measurements through walls are also reported and compared with the theory. Lastly, electrically small circularly polarized antennas are investigated as a means of alleviating orientation dependence in near-field wireless power transfer. An electrically small turnstile dipole antenna is designed by utilizing top loading and multiple folding. The circularly polarization characteristic of the design is first tested in the far field, before the antennas are placed in the radiating near-field region for wireless power transfer. It is shown that such circularly polarized antennas can lessen orientation dependence in near-field coupling. / text

Thermophotovoltaic (TPV) devices, also known as (nano-TPVs) are energy-conversion systems which generate electric current from thermal radiation energy by a heat source. Although their conversion efficiency is limited in the far field by the Schockley-Queisser limit, in near field the heat flux transferred to a TPV cell can be significantly enchanced due to the contribution of evanescent waves, in particular supporting a surface mode. Unfortunately, spectral mismatch between the emitter and the TPV cell spectrum limits the TPV conversion efficiency. Photons with energy lower than the TPV cell bandgap may not be able to create electron-hole pairs because mobile carriers start diffusing and drifting between conductance and valence band, and try to exceed the upper limit of the band. This destroys the thermal equilibrium of the semiconductor and results in excess heat. Also, for high energy photons, the difference between the photon's energy and the bandgap energy is lost in Joule heating. Thus, quasimonochromatic, narrow-band and coherent emitters at a frequency near the energy bandgap of the converter is an ideal source to achieve high conversion efficiency. Nano-TPV device consisting of tungsten thermal emitter, maintained at 1200K, and the cell made of GaInAsSb are considered; thermal management system is reviewed assuming a constant heat flux boundary due to heat generation by the cell with a fluid temperature fixed at 293K. Tungsten thermal selective emitters are designed, characterized and optimized based on two-dimensional (2D) tungsten PhC by controlling periodic triangular grooves such that channel plasmon polaritons (CPPs) are coupled efficiently into these grooves to excite a localized groove modes which are well-matched to the GaInAsSb cell external quantum efficiency (EQE). The results show that power output and the 2D TE normal efficiency of the system are predicted to be 0.82x10⁴ W/m² and 43.8%, respectively. This leads to a promising device for many different sectors such as military, space and semiconductor industry. / text

Not available / text

The master´s thesis project was performed in collaboration with the design and engineering company Eker Design from Fredrikstad in Norway, who is designing and developing flip cover NFC keyboards for smartphones. The new product idea is the full-sized NFC desktop keyboard for public institutions to offer to pupils, students or business people for instance. The thesis project is examining how such a product can be designed and should be designed in order to fit into its market and environment to meet the target group´s interest in order to be successful. With a human-centered design approach the project work was starting by the user and the market. The work consisted of analyzing and emphasizing with the market which mainly included the users, the competitors and the trends within a market analysis and a survey research. From the findings and insights of the research phase a design strategy and a business model for the new keyboard was created and communicated via a design brief. Different ideas and concepts were created, tested and presented via concept sketches along with mock-ups. The final concepts were evaluated via a concept evaluation in relation to the requirements of the business and user value. The final concept was developed and designed via the CAD software SolidWorks and the rendering software Keyshot. The design and development phase was focusing on functionality, usability, materials, surfaces, textures and the mechanical and technical solutions for the design. The result of this thesis project is named TRANSIT and is presenting how a collapsible desktop keyboard which is offering a NFC connection could look like and work to offer to people in public places such as libraries or universities and be as well be suitable for people to use at home. The TRANSIT keyboard is a simple and robust concept of a full-sized tactile keyboard which is offering a NFC connection as well as a Bluetooth connection for devices which do not support NFC yet. The design is aimed for smartphones and tablets and is offering a support which consists of an automated stand and a back plate which angle is adjustable step-less. The design allows to collapse stand, keyboard and back plate into a compact package which makes it easy to store and transport. Furthermore the design is providing a charging option for the smart device via energy harvesting or cable and has therefore internal batteries.   The project is ending with the final presentation of the physical model in scale 1:1. / Detta examensarbete genomfördes i samarbete med design och ingenjörsföretaget Eker design från Fredriksstad i Norge, som designar och utvecklar flipcover NFC tangentbord till smartphones. Den nya produktidén är ett fullstort stationärt NFC tangentbord för offentliga institutioner, tänkt att användas av till exempel elever, studenter eller affärsmänniskor. Detta examensarbete undersöker hur ovan nämnda produkt kan och bör designas för att passa dess målmarknad och möta målgruppens intresse för att bli framgångsrik. Med en Human-centered design approach, började projektet med att utgå från användaren och marknaden. Arbetet bestod i att analysera och empatisera med marknaden som huvudsakligen bestod av användare och konkurrenterna, samt att undersöka trender genom en marknadsundersökning. Med utgångspunkt från de insikter som uppkom genom projektets utforskningsfas, skapades en design strategi och en affärsmodell för det nya tangentbordet i form av en design brief. Olika idéer och koncept skapades, testades och presenterades via koncept skisser och mock-ups. Det slutgiltiga konceptet utvecklades och designades med hjälp av CAD programvaran SolidWorks och renderingsprogrammet Keyshot. Design och utvecklingsfasen fokuserade på funktionalitet, användbarhet, material, ytor, texturer och mekaniska och tekniska lösningar för designen. Den slutgiltiga produkten heter TRANSIT och visar på hur ett hopfällbart stationärt tangentbord som erbjuder en NFC-anslutning skulle kunna se ut och fungera för människor som arbetar på olika platser i det publika rummet, som på bibliotek eller universitet. Men även för privat användning i hem. TRANSIT tangentbordet är ett enkelt och robust koncept av ett fullstort taktilt tangentbord som erbjuder en NFC-koppling såväl som Bluetooth for enheter som ännu inte stöder NFC. Designen, som är riktad mot smartphones och tablets, har ett ställ som består av ett automatiskt stöd och en bakplatta med steglös justering. Designen gör att tangentbordet, stödet och bakplattan går att fälla ihop till ett kompakt paket som är enkelt att transportera och förvara. Dessutom erbjuds möjligheter att ladda smart-enheter via energi-skördning eller kabel då enheten har inbyggda batterier. Projektet avslutades med en slutpresentation av en fysisk modell i skala 1:1.

Microwave near-field probes (MNPs) confine evanescent fields to regions that are substantially smaller than the wavelength at the operation frequency. Such probes are able to resolve subwavelength features, thus providing resolution much higher than the classical Abb?? limit. These abilities of MNPs are primarily due to the evanescent nature of the field generated at the tip of the probes. In the past, MNPs with ultra-high resolution were designed by tapering a resonant opening to provide high field concentration and high sensitivity. The limitations of these MNPs were subject to low surface roughness and practical realization challenges due to their geometrical features and vibration control constraints. Metamaterials with their ability to enhance evanescent fields, lead to the speculation that they could potentially increase the sensitivity of near-field probe. Periodically arranged metamaterial unit elements such as split-ring-resonators (SRRs) can create negative permeability media. Placing such material layer in the proximity of a probe leads to enhancement of the evanescent waves. Guided by this remarkable feature of metamaterials, I proposed an MNP consisting of a wire loop concentric with a single SRR. The evanescent field behavior of the probe is analyzed using Fourier analysis revealing substantial enhancement of the evanescent field consistent with metamaterial theory predictions. The resolution of the probe is studied to especially determine its ability for sub-surface detection of media buried in biological tissues. The underlying physics governing the probe is analyzed. Variations of the probe are developed by placement of lumped impedance loads. To further increase the field confinement to smaller region, a miniaturized probe design is proposed. This new probe consists of two printed loops whose resonance is tunable by a capacitor loaded in the inner loop. The sensing region is decreased from ??/20 to ??/55, where ?? is the wavelength of the probe???s unloaded frequency. The magnetic-sensitive nature of the new probe makes it suitable for sensing localized magnetostatic surface resonance (LMSR) occurring in electrically very small particles. Therefore, I proposed a sensing methodology for detecting localized magnetostatic surface (LMS) resonant particles. In this methodology, an LMS resonant sphere is placed concentrically with the loops. A circuit model is developed to predict the performance of the probe in the presence of a magnetic sphere having Lorentz dispersion. Full-wave simulations are carried out to verify the circuit model predictions, and preliminary experimental results are demonstrated. The Lorentzian fit in this work implies that the physical nature of LMSR may originate from spin movement of charged particle whose contribution to effective permeability may be analogous to that of bound electron movement to effective permittivity in electrostatic resonance. Detection of LMSR can have strong impact on marker-based sensing applications in biomedicine and bioengineering.