Avec l'explosion de l'Internet des Objets (IoT), de nouveaux dispositifs permettant de tagguer les objets sont nécessaires afin de permettre non seulement leur identification mais aussi d'assurer des communications fiables et de nouvelles fonctionnalités comme la détection, la localisation ou la capture d'informations. Cette tendance s'appuie sur la technologie bien établie qu'est la radiofréquence par identification (RFID) et donc l'utilisation d'étiquettes (ou tags) faibles coûts et télé-alimentés. Dans ce contexte, de nombreux travaux au niveau de la couche d'application se tournent vers la mise au point de traitements logiciels complémentaires visant à produire de nouveaux types d'information. D'autres travaux visent à améliorer la couche physique avec l'objectif de miniaturiser encore le tag mais aussi de le doter de nouvelles capacités. Jusqu'à présent, il n'existe quasiment pas de travaux concernant la transmission du signal et aucun sur l'exploitation du comportement non-linéaire des puces RFID. Cette thèse vise à étudier les phénomènes non-linéaires produits lors d'une communication RFID.Dans la première partie, deux plateformes de mesure et de caractérisation spécifiques ont été développées : la première vise à observer les signaux au cours d'une communication RFID, et alors caractériser et analyser les effets liés aux phénomènes non linéaires ; la seconde permet d'effectuer différentes mesures directement sur les puces et les caractériser en termes d'impédance, production d'harmoniques et sensibilité. Ces plateformes ont permis : 1) de mettre en évidence que les fréquences harmoniques sont porteuses d'informations qui peuvent être exploitées et même offrir de nouvelles fonctionnalités ; 2) d'obtenir de nombreuses informations sur les propriétés des puces et d'en établir un modèle électrique précis ; 3) de déterminer des critères permettant d'évaluer la performance des tags dans le contexte étudié.Dans la deuxième partie, plusieurs nouveaux tags RFID ont été conçus, fabriqués, mesurés et évalués. Ces nouveaux tags fonctionnent non seulement dans la bande UHF mais aussi sont adaptés à la troisième harmonique dans la bande des microondes. Une méthodologie et des lignes directives d'aide à la conception de ce type de tags ont été établies et s'appuient sur les deux plateformes développées afin de caractériser les différents éléments. Dans un même temps, les effets liés à la fabrication ont aussi été étudiés et des études paramétriques ont permis de mettre en évidence l'effet sur les performances de la géométrie de l'antenne et du type de puce utilisée.Dans une troisième partie, les études se sont focalisées à exploiter les effets non-linéaires des dispositifs de redressement. L'idée générale est de coupler la RFID passive avec les dispositifs de transferts de puissance et de récupération d'énergie avec pour objectifs 1) de maximiser l'efficacité de conversion RF – continu 2) et d'augmenter la distance de lecture des tags passifs. Plusieurs prototypes ont été réalisés et leurs performances ont été démontrées.L'ensemble de ces travaux a mis en évidence un nouveau concept de communication RFID exploitant les non-linéarités générées par les puces RFID. Ce concept ouvre la voie à de nouvelles applications. et a fait l'objet d'une demande de brevet international. / Powered by the exploding popularity of the Internet-of-Things (IoT), the demand for tagged devices with labels capable to ensure a reliable communication with added functions beyond the identification, such as sensing, location, health-care, among others, is growing rapidly. Certainly this growing is headed by the well-established Radio Frequency Identification (RFID) technology, and the use of wireless low-cost self-powered tags, in other words passive RFID tags, is the most widespread used alternative. In the constant evolution on this field, usually new software treatments are offered at the application layer with the objective to processing data to produce some new information. Further works aimed at improving the physical layer around the tag antenna miniaturization and matching techniques. So far, little or no work had been done on the exploitation of the communication channel, and certainly none has been done on the exploitation of the non-linear behavior of RFID chips.After presenting the RFID technology and phenomena produced by Radio Frequency (RF) non-linear devices, and leaning in some nearby works on the field, the core of this thesis starts by exposing two characterization platforms for the evaluation of non-linear phenomena presented during the reader-tag communication. One is specialized in radiating measurements considering the whole tag (antenna and chip) under test. The other is specialized in conducted measurements directly over RFID chips, allowing performing different parametric studies (power dependency, impedance, harmonic production, sensitivity). The characterization results show that harmonic signals generated from the passive RFID chip carry information.By exploiting the characterization results and to verify the hypothesis of exploitation of non-linearities in RFID, i.e. the use of harmonic signals, the research is pursued by designing, fabricating, and measuring four different configurations of RFID tags. The new RFID tags operate at the fundamental frequency in the UHF band and at its $3^{rd}$ harmonic in the microwave band. Antenna design policies, fabrication details, and parametric studies on the performance of the new prototypes are presented. The parametric study takes special care in the antenna structure, kind of chip used, received power, and read range.Finally, some alternatives approaches for the exploitation of non-linear effects generated by rectifying devices are presented. Some theoretical aspects and experimental results are discussed linking the passive RFID technology to the theories of Wireless Power Transfer (WPT) and Electromagnetic Energy Harvesting (EEH). The solution takes advantage of the non-linear nature of rectifying elements in order to maximize the RF-to-DC conversion efficiency of EEH devices and increase the read range of passive RFID tags. The solution triggers on the design of a RF multi-device system. The design procedure and tests consider three non-linear phenomena: (1) the impedance power dependency, (2) the harmonic production, and (3) the rectifying dependence on the RF waveform.

Abstract The Internet of Things (IoT) is already providing solutions to various tasks related to monitoring the environment and controlling devices over wired and wireless networks. It is estimated by several well-known research facilities that the number of IoT devices will be in the order of tens of billions by 2020. This inevitably brings challenges and costs in deployment, management, and maintenance of networks. The focus of this thesis is to provide solutions that mainly help in the deployment and maintenance of various wireless IoT networks. Different applications have different requirements for a wireless link coverage. It is important to utilize suitable radio technology for a particular application in order, e.g., to maximize the lifetime of a device. A wireless body area network (WBAN) typically consists of devices that are within couple of meters from each other. The WBAN is suitable for, e.g., measuring muscle activity and transferring data to a storage for processing. The wireless link can use air as a medium, or alternatively, an induced electric field to a body can be used. In this thesis, it is shown that a location of the electrodes in the body have impact to the attenuation. Home automation IoT applications are typically implemented with mid-range wireless technologies, known as wireless personal area networks (WPAN). In order to minimize and get rid of battery change operations, a wake-up receiver could be utilized in order to improve the device’s energy efficiency. The concept is introduced and performance of the current state-of-the-art works are presented. In addition, a control loop enabling a passive device to have control over an energy source is proposed. Applications that have low bandwidth requirements can be implemented with low-power wide area networks (LPWAN). One technology – LoRaWAN – is evaluated, and it is recommended as based on the results to use it in non-critical applications. / Tiivistelmä Esineiden internet (Internet of Things, IoT) mahdollistaa jo laajan kirjon erilaisia ratkaisuja ympäristön monitorointiin ja laitteiden hallintaan hyödyntäen sekä langattomia että langallisia verkkoja. Usea hyvin tunnettu tutkimusorganisaatio on arvioinut, että vuonna 2020 IoT laitteiden määrä tulee olemaan kymmenissä miljardeissa. Se luo väistämättä haasteita laitteiden sijoittamisessa, hallinnassa ja kunnossapidossa. Tämä väitöskirja keskittyy tarjoamaan ratkaisuja, jotka voivat helpottaa langattomien IoT laitteiden sijoittamisessa ja kunnossapidossa. IoT sovellusten laaja kirjo vaatii erilaisia langattomia radioteknologioita, jotta sovellukset voitaisiin toteuttaa, muun muassa, mahdollisimman energiatehokkaasti. Langattomassa kehoverkossa (wireless body area network, WBAN) käytetään usein hyvin lyhyitä langattomia linkkejä. WBAN on soveltuva esimerkiksi lihasten aktiivisuus mittauksessa ja mittaustiedon siirtämisessä talteen varastointia ja prosessointia varten. Linkki voidaan toteuttaa käyttäen ilmaa rajapintana, tai vaihtoehtoisesti, kehoa. Tässä työssä on näytetty, että käytettäessä kehoa siirtotienä, elektrodien sijainnilla on merkitystä signaalin vaimennuksen kannalta. Kotiautomaatio IoT sovellukset ovat tyypillisesti toteutettu käyttäen langatonta likiverkkoa, jossa linkin pituus sisätiloissa on alle 30 metriä. Jotta päästäisiin eroon pariston vaihto-operaatiosta tai ainakin vähennettyä niiden määrää, herätevastaanotinta käyttämällä olisi mahdollista parantaa laitteiden energiatehokkuutta. Herätevastaanotin konsepti ja tämänhetkistä huipputasoa edustavien vastaanottimien suorituskyky ovat esitetty. Lisäksi, on ehdotettu menetelmä joka takaa energian saannin passiiviselle IoT laitteelle. IoT sovellukset jotka tyytyvät vähäiseen kaistanleveyteen voidaan toteuttaa matalatehoisella laajan alueen verkolla (low-power wide area network, LPWAN). Yhden LPWAN teknologian, nimeltään LoRaWAN, suorituskykyä on evaluoitu. Tulosten perusteella suositus on hyödyntää kyseistä teknologiaa ei-kriittisissä sovelluksissa.

Resource allocation in wireless networks is one of the most studied class of problems. Generally, these problems are formulated as utility maximization problems under relevant constraints. The challenges posed by these problems vary widely depending on the nature of the utility function under consideration. Recently, the widespread prevalence of wireless devices prompted researchers and engineers to delve into the security issues of wireless communication. As compared to the wired medium, ensuring security for the wireless medium is more challenging mainly due to the broadcast nature of the transmission. But the ongoing research on physical layer security promises robust and reliable security schemes for wireless communication. Contrary to conventional cryptographic schemes, physical layer security techniques are impregnable as the security is ensured by the inherent randomness present in the wireless medium. In this thesis, we consider several wireless scenarios and propose secrecy enhancing resource allocation schemes for them in the first few chapters. We initially address the problem of secure transmission by following the conventional approach in the secrecy literature|secrecy rate maximization. Needless to say, in these chapters, secrecy rate is the utility function and the constraints are posed by the available power budget. Then we consider a pragmatic approach where we target the signal-to-noise ratio (SNR) of participating nodes and ensure information secrecy by appropriately constraining the SNRs of those nodes. In those SNR based formulations, SNR at the destination is the utility function and we are interested in maximizing it. In the last two chapters, we study two scenarios in a non-secrecy setting. In one of them, end-to-end data rate is the utility, whereas, in the other one, two utility functions|based on revenue generated|are defined for two rational agents in a game-theoretic setting. In the second chapter, we study parallel independent Gaussian channels with imperfect channel state information (CSI) for the eavesdropper. Firstly, we evaluate the probability of zero secrecy rate in this system for (i) given instantaneous channel conditions and (ii) a Rayleigh fading scenario. Secondly, when non-zero secrecy is achievable in the low SNR regime, we aim to solve a robust power allocation problem which minimizes the outage probability at a target secrecy rate. In the third, fourth and fifth chapters, we consider scenarios where the source node transmits a message to the destination using M parallel amplify-and-forward (AF) relays in the presence of a single or multiple eavesdroppers. The third chapter addresses the problem of the maximum achievable secrecy rate for two specific network models: (a) degraded eavesdropper channel with complex channel gain and (b) scaled eavesdropper channel with real-valued channel gains. In the fourth chapter, we consider the SNR based approach and address two problems: (i) SNR maximization at the destination and (ii) Total relay power minimization. In the fifth chapter, we assume that the relay nodes are untrusted and to counter them, we deliberately introduce artificial noise in the source message. For this model, we propose and solve SNR maximization problems for the following two scenarios: (i) Total power constraint on all the relay nodes and (ii) Individual power constraints on each of the relay nodes. In the sixth chapter, we address the problem of passive eavesdroppers in multi-hop wire-less networks using the technique of friendly jamming. Assuming decode-and-forward (DF) relaying, we consider a scheduling and power allocation (PA) problem for a multiple-source multiple-sink scenario so that eavesdroppers are jammed, and source-destination throughput targets are met. When channel state information (CSI) of all the node are available, we intend to minimize the total power consumption of all the transmitting nodes. In the absence of eavesdroppers CSI, we minimize vulnerability region of the network. In chapter seven, the problem of cooperative beamforming for maximizing the achievable data rate of two-hop amplify-and-forward (AF) network (in the absence of eavesdropper(s)) is considered. Along with an individual power constraint on each of the relay nodes, we consider a weighted sum power constraint. To solve this problem, we propose a novel algorithm based on the Quadratic Eigenvalue Problem (QEP) and discuss its convergence. In chapter eight, we study a Stackelberg game between a base station and a multi-antenna power beacon for wireless energy harvesting in a multiple sensor node scenario. Assuming imperfect CSI between the sensor nodes and the power beacon, we propose a utility function that is based on throughput non-outage probability at the base station. We find the optimal strategies for the base station and the power beacon that maximize their respective utility functions.

Les systèmes de récupération d'énergie sont prometteurs pour l'auto-alimentation des dispositifs intégrés. Les matériaux pyroélectriques couplant un changement de température à un changement de polarisation électrique peuvent être utilisés pour la conversion de l'énergie thermique en énergie électrique sans nécessité de maintien de gradients thermiques qui constitue un inconvénient majeur dans les modules thermoélectriques compacts. Dans cette thèse, le PbZro.52Tio.48O3 (PZT) et le BaxSr1-xTiUO3 (x = l et x = 0.7) à fort coefficients pyroélectriques, sont choisis, élaborés en couches minces épitaxiées, caractérisés pour étudier leur potentiel de récupération d'énergie thermique. Ce travail comporte deux aspects : le premier consiste au développement et l'optimisation des conditions de croissance des hétérostructures intégrées et épitaxiées sur silicium. Le deuxième est focalisé sur l'étude des propriétés fonctionnelles (ferroélectriques, diélectriques et pyroélectriques) et à l' estimation du pouvoir de récupération d'énergie principalement des couches de PZT. Une corrélation entre ces deux aspects est ainsi présente. Un changement de la structure cristalline est montré sur les empilements intégrés sur Si, en comparaison avec des structures équivalentes réalisées sur substrat de STO. L'impact de ceci a été directement constaté sur les propriétés fonctionnelles des couches hétéroépitaxiées de PZT. Ainsi une anisotropie importante de ces propriétés a pu être mise en évidence, en complétant cette étude par des mesures dans le plan a l'aide de peignes interdigités. Ces observations ont été cohérentes avec les mesures de la diffraction des rayons X en fonction de la température. Par ailleurs, les différentes méthodes et configurations de mesures du coefficient pyroélectrique sur PZT ont permis une meilleure compréhension du phénomène et la distinction des diverses contributions existantes. La mesure statique indirecte issue de la variation de la polarisation rémanente en fonction de la température renseigne sur l'effet pyroélectrique intrinsèque (et secondaire). Cependant les mesures dynamiques du courant pyroélectrique pendant un changement de la température contiennent toutes les contributions pyroélectriques et non pyroélectriques, comme les effets extrinsèques et le courant de relaxation. Des mesures pyroélectriques dynamiques sous champ électrique, se rapprochant des conditions de cycles de récupération d'énergie thermique, ont permis de montrer que des courants de conduction apparaissaient même pour des bonnes couches de PZT diélectriques épaisses. Ces courants masquent les courants pyroélectriques et rendent l'application de générateur électrique par cycles thermodynamiques sous champ électrique rédhibitoire. Des composants passifs n'utilisant pas ou peu de champs électriques tels que des capteurs devront plutôt être envisagées. / Due to the wasted heat in ever more compact microelectronic devices, the harvesting of thermal energy has become interesting for self-powering small devices. Consequently, pyroelectric materials witch couple a change in temperature to a change in electrical polarization may be used for the conversion of the thermal energy to an electric energy without necessity of maintaining thermal gradients that is a main drawback in compact devices with thermoelectric materials. In this thesis, PbZro.52Tio.48O3 (PZT) and BaxSr1-xTiUO3 (x = l and x = 0.7), with high pyroelectric coefficients are chosen, elaborated in thin epitaxial layers, characterized structurally and electrically to study their potential for thermal energy harvesting. This work has two aspects: the first consists in the development and optimization of the growth conditions of epitaxial heterostructures integrated on Si. The second one focuses on the study of the functional properties ( ferroelectric, dielectric and pyroelectric) and the estimation of the energy harvesting efficiency mainly of PZT layers. A correlation between these two aspects is then done. A change in the crystal structure is shown on the Si-integrated stacks in comparison with equivalent structures grown on STO substrate. This structural behavior impacts directly the functional properties of the heteroepitaxial layers of PZT. Th us, an important anisotropy of these properties was demonstrated and completed by a study of the in plane properties using measurements by interdigital capacitors. These observations were consistent with measurements of X - ray diffraction as a function of temperature. Otherwise, different methods and configurations of pyroelectric coefficient measurements on PZT have allowed a better understanding of the phenomenon and the distinction of the various existing contributions. The indirect static measurement resulting from the variation of the remnant polarization as a function of the temperature gives the intrinsic (and secondary) pyroelectric contributions. However, the dynamic measurements of the pyroelectric current during a change of the temperature contain all the pyroelectric and non-pyroelectric contributions, such as the extrinsic effects and the relaxation current . Dynamic pyroelectric measurements under an electric field are near to the conditions of thermal energy harvesting cycles. Conduction currents appeared, even for good layers of thick dielectric PZT, and mask the pyroelectric currents. This makes the application of electric generator by thermodynamic cycles under electric field prohibitive. Passive components using low or no electrical field such as sensors should be considered.

Inductive power transfer (IPT) systems with tolerance to the lateral misalignment are advantageous for enhancing the transmitted power, usability and security of the system. In this thesis, a misalignment tolerant multi-coil design is proposed to supply stationary and dynamic battery-free wireless devices. A compact architecture composed of individually switchable 3 layers of printed coils arranged with overlap for excellent surface coverage. A hybrid architecture based on three compact AC supply modules reduces the supply circuit complexity on the sending Seite 2 von 4side. It detects the position of the receiver coil quickly, controls the activation of the transmitting coils and estimates the next receiver position. The proposed architecture reduces the circuit footprint by a factor of 62% compared to common architectures. A transmitter coil activation strategy is proposed based on the detection of the transmitting coils voltage and communication between sending side and receiving side to detect devices to supply nature and position and to differentiate them from other conductive objects in the sending area to the supplying security. The experimental results prove that the proposed architecture has a good performance for different trajectories when the device speed does not exceed 15 mm/s. Besides, the maximum detection time for the initial device position is about 1.6 s. The maximal time interval to check the transmitter coils is around 0.7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOOK / Induktive Energieübertragungssysteme (IPT) mit Toleranz gegenüber seitlichem Versatz sind vorteilhaft, um die übertragene Leistung, die Nutzbarkeit und die Sicherheit des Systems zu verbessern. In dieser Arbeit wird ein versatztolerantes Multispulen-Design vorgeschlagen, um stationäre und dynamische batterielose drahtlose Geräte zu versorgen. Die kompakte Architektur besteht aus 3 einzeln schaltbaren Schichten gedruckter Spulen, die überlappend angeordnet sind, um eine hervorragende Oberflächenabdeckung zu gewährleisten. Eine hybride Architektur, die auf drei kompakten AC-Versorgungsmodulen basiert, reduziert die Komplexität der Versorgungsschaltung auf der Senderseite. Sie erkennt die Position der Empfängerspule schnell, steuert die Aktivierung der Sendespulen und schätzt die nächste Empfängerposition. Die vorgeschlagene Architektur reduziert den Platzbedarf der Schaltung um einen Faktor von 62 % im Vergleich zu herkömmlichen Architekturen. Es wird eine Aktivierungsstrategie für die Sendespulen vorgeschlagen, die auf der Erkennung der Spannung der Sendespulen und der Kommunikation zwischen Sende- und Empfangsseite basiert, um die Art und Position der zu versorgenden Geräte zu erkennen und sie von anderen leitfähigen Objekten im Sendebereich zu unterscheiden. Die experimentellen Ergebnisse zeigen, dass die vorgeschlagene Architektur eine gute Leistung für verschiedene Trajektorien hat, wenn die Geschwindigkeit der Geräte 15 mm/s nicht überschreitet. Außerdem beträgt die maximale Erkennungszeit für die anfängliche Geräteposition etwa 1,6 s. Das maximale Zeitintervall für die Überprüfung der Senderspulen beträgt etwa 0,7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOOK

Indiana University-Purdue University Indianapolis (IUPUI) / A gearless hydraulic wind energy transfer system utilizes the hydraulic power transmission principles to integrate the energy of multiple wind turbines in a central power generation location. The gearless wind power transfer technology may replace the current energy harvesting system to reduce the cost of operation and increase the reliability of wind power generation. It also allows for the integration of multiple wind turbines to one central generation unit, unlike the traditional wind power generation with dedicated generator and gearbox. A Hydraulic Transmission (HT) can transmit high power and can operate over a wide range of torque-to-speed ratios, allowing efficient transmission of intermittent wind power. The torque to speed ratios illustrates the relationship between the torque and speed of a motor (or pump) from the moment of start to when full-load torque is reached at the manufacturer recommended rated speed. In this thesis, a gearless hydraulic wind energy harvesting and transfer system is mathematically modeled and verified by experimental results. The mathematical model is therefore required to consider the system dynamics and be used in control system development. Mathematical modeling also provided a method to determine the losses of the system as well as overall efficiency. The energy is harvested by a low speed-high torque wind turbine connected to a high fixed-displacement hydraulic pump, which is connected to hydraulic motors. Through mathematical modeling of the system, an enhanced understanding of the HTS through analysis was gained that lead to a highly efficient hydraulic energy transmission system. It was determined which factors significantly influenced the system operation and its efficiency more. It was also established how the overall system operated in a multiple wind turbine configuration. The quality of transferred power from the wind turbine to the generator is important to maintaining the systems power balance, frequency droop control in grid-connected applications, and to ensure that the maximum output power is obtained. A hydraulic transmission system can transfer large amounts of power and has more flexibility than a mechanical and electrical system. However high-pressure hydraulic systems have shown low efficiency in wind power transfer when interfaced with a single turbine to a ground-level generator. HT’s generally have acceptable efficiency at full load and drop efficiency as the loading changes, typically having a peak around 60%. The efficiency of a HT is dependent on several parameters including volumetric flow rate, rotational speed and torque at the pump shaft, and the pressure difference across the inlet and outlet of the hydraulic pump and motor. It has been demonstrated that using a central generation unit for a group of wind turbines and transferring the power of each turbine through hydraulic system increases the efficiency of the overall system versus one turbine to one central generation unit. The efficiency enhancement depends on the rotational speed of the hydraulic pumps. Therefore, it is proven that the multiple-turbine hydraulic power transfer system reaches higher efficiencies at lower rotational speeds. This suggests that the gearbox can be eliminated from the wind powertrains if multiple turbines are connected to the central generation unit. Computer simulations and experimental results are provided to quantify the efficiency enhancements obtained by adding the second wind turbine hydraulic pump to the system.

<p>Micro- and nanoparticles (MNP) attract much attention owing to their unique properties, structural tunability, and wide range of practical applications. To deposit these important materials on surfaces for generating functional coatings, a variety of special delivery systems and coating/printing techniques have been explored. Herein, spray coating technique is a promising candidate to advance the field of nanotechnology due to its low-cost, high-deposition rate, manufacturing flexibility, and compatibility with roll-to-roll processing. Despite great advances, direct scalable spray writing of functional materials at high-spatial resolution through fine patterning without a need of vacuum and mask equipment still remains challenging. Addressing these limitations requires the development of efficient spray deposition techniques and novel manufacturing approaches to effectively fabricate functional coatings. To this end, this dissertation employs three different spray coating methods of (1) cold spray; (2) atomization-assisted supersonic spray, and (3) dual velocity regime spray to address the aforementioned limitations. A comprehensive set of coating materials, design principles, and operational settings for each spray system are tailored for rapid, direct, and sustainable deposition of MNP on various substrates. Besides, through the two-phase flow modeling, droplets dispersion and deposition characteristics were investigated under both subsonic and supersonic flow conditions to uncover the process-structure-property relationships of the established spray systems. Moreover, novel spray-based manufacturing approaches are developed to fabricate functional coatings in various applications, including (i) functional polymer metallization, (ii) printed flexible electronics, (iii) advanced thin-film nanocoating, (iv) laser direct writing, and (v) electronic textiles.</p>

<p dir="ltr">Structural instability, traditionally deemed undesirable in engineering, can be leveraged for beneficial outcomes through intelligent design. One notable instance is elastic buckling, often leading to structures with two stable equilibria (bistable). Connecting bistable elements to form multistable mechanical metamaterials can enable the discretization and offer tunability of mechanical properties without the need for continuous energy input.<i> </i>In this work, we study the physics of these multistable metamaterials and utilize their state and property alterations along with snap-through instabilities resulting from state change for engineering applications. These materials hold potential for diverse applications, including mechanical and thermo-mechanical defrosting, energy absorption, energy harvesting, and mechanical storage and computation.</p><p dir="ltr">Focusing on defrosting, we find that the energy-efficient mechanical method using embedded bistable structures in heat exchanger fins significantly outperforms the thermal methods. The combination of manufacturing methods, material choice, boundary conditions, and actuation methodologies is systematically investigated to enhance defrosting performance. A purely mechanical strategy is effective against solid, glaze-like ice accumulations; however, performance is substantially diminished for low-density frost. To address this limitation, we study frost formation on the angular shape morphing fins and subsequently introduce a thermo-mechanical defrosting strategy. This hybrid approach focuses on the partial phase transition of low-density frost to solid ice through thermal methods, followed by mechanical defrosting. We experimentally validate this approach on a multistable heat exchanger fin pack.</p><p dir="ltr">Recent advancements have led to a new paradigm of reusable energy-absorbing materials, known as Phase Transforming Cellular Materials (PXCM) that utilize multiple negative stiffness elements connected in series. We explore the feasibility of this multistable metamaterial as frequency up-conversion material and utilize these phase transformations for energy harvesting. We experimentally demonstrate the energy-harvesting capabilities of a phase-transforming unit-cell-spring configuration and investigate the potential of multicell PXCM as an energy harvesting material.</p><p dir="ltr">The evolution towards intelligent matter, or physical intelligence, in the context of mechanical metamaterials can be characterized into four distinct stages: static, responsive, adaptive, and intelligent mechanical metamaterials. In the pursuit of designing intelligent mechanical metamaterials, there has been a resurgence in the field of mechanical computing. We utilize multistable metamaterials to develop mechanical storage systems that encode memory via bistable state changes and decode it through a global stiffness readout. We establish upper bounds for maximum memory capacity in elastic bit blocks and propose an optimal stiffness distribution for unique and identifiable global states. Through both parallel and series configurations, we realize various logic gates, thereby enabling in-memory computation. We further extend this framework by incorporating viscoelastic mechano-bits, which mimic the decay of neuronal action potentials. This allows for temporal stiffness modulation and results in increased memory storage via non-abelian behavior, for which we define a fundamental time limit of detectability. Additionally, we investigate information entropy in both elastic and viscoelastic systems, showing that temporal neural coding schemes can extend the system’s entropy beyond conventional limits. This is experimentally validated and shown to not only enhance memory storage but also augment computational capabilities.</p><p dir="ltr">The work in this thesis establishes multistability as a key design principle for developing responsive, adaptive, and intelligent materials, opening new avenues for future research in the field of multistable metamaterials.</p>

[pt] A necessidade de transmitir energia e dados através de barreiras metálicas tem sido cada vez maior em aplicações industriais, onde não é possível a penetração de cabos elétricos, ou o uso de ondas eletromagnéticas, tais como, por exemplo, em sistemas de sensoriamento de cimentação em poços de petróleo. Ondas acústicas podem ser uma solução para esse problema, porque não são afetadas pelo efeito gaiola de Faraday, além de possuírem baixa atenuação ao atravessarem metais. Diversos esforços foram feitos para realizar a transmissão de dados através de camadas metálicas, com abordagens que variam em composição do canal acústico, taxa de transmissão, transmissão simultânea de dados e energia e complexidade dos circuitos empregados; existe, porém, carência de trabalhos que envolvam camadas metal-fluído-metal. Este trabalho apresenta uma possível solução utilizando ondas acústicas como meio de transportar energia e dados em um canal composto de barreiras com duas camadas metálicas e uma de fluído. Aqui propõe-se uma inovadora técnica de controle automático de ganho e um melhor aproveitamento da largura de banda do canal acústico, que permite maior taxa de transmissão de dados. É ainda proposta uma técnica para controle dinâmico da portadora enviada ao lado passivo do sistema. Inicialmente, foi feita uma análise de um modelo numérico, baseado em trabalhos anteriores, fundamentado na propagação de ondas acústicas e baseado na analogia acustoelétrica. Em seguida, desenvolveu-se um sistema eletrônico para receber / transmitir energia e dados digitais, modulados em frequência, de um lado ao outro do sistema. Por fim, análises experimentais foram feitas utilizando como canal acústico, um conjunto de duas placas planas de aço (de 5 mm) separadas por uma camada de fluído (de 100 mm) e dois transdutores alinhados axialmente, realizando a transferência de energia e dados digitais modulados em frequência. O sistema foi capaz de realizar a transferência de dados a uma taxa de 19200 bps e simultaneamente uma transferência de energia de 66 mW, com essa energia foi possível alimentar o modulo eletrônico e um sensor de pressão e temperatura. Durante os testes foi constatado um aproveitamento de 5,5 por cento da energia aplicada ao canal, e foi possível atingir uma taxa de erro de bit de 5 por cento em um teste com 2 h e 30 min de duração, utilizando o canal acústico com camadas de múltiplos materiais propostos. O sistema de controle de portadora funcionou adequadamente, permitindo uma redução de consumo de até 53 por cento. O controle automático de ganho permitiu uma redução de 50 por cento na taxa de erro de decodificação. Demonstra-se, então, a viabilidade de tais sistemas de controle propostos, os quais podem ser úteis em casos onde existam variações nas características acústicas do canal em questão que, em conjunto com a transferência não intrusiva, pode prover solução para sistemas de sensoriamento. / [en] The need for energy and data transmission through metallic barriers is increasing in industrial applications, where the penetration of electrical waves or the use of electrical waves is not possible. An example of such a scenario is the monitoring of cementing in wellbore applications. Acoustic waves are promising to solve this problem, since they are not affected by the Faraday cage effect, in addition, they present low attenuation when propagating in metals. Several efforts have been made to carry out data transmission through metallic layers, with approaches that vary in composition of the acoustic channel, transmission speed, simultaneous transmission of data and energy and the complexity of the circuits used, but there is a lack of works involving metal-fluid-metal layers. This work presents a possible solution using acoustic waves as a mean of transporting energy and data in a channel composed of barriers with two metallic layers and one fluid layer. Here, it is proposed a novel technique for automatic gain control and better use of the available bandwidth of the acoustic channel, which allows higher data transmission speed. Also, a technique for dynamic control of the carrier sent to the passive side of the system is proposed. Initially, an analysis with a numerical model was made, following previous works, which is based on the propagation of acoustic waves and relying on the acoustoelectric analogy. Then, an electronic system was developed to receive/transmit power and digital data, frequency modulated, from one side of the system to the other. Finally, experimental analyzes were performed using as an acoustic channel, a set of two flat steel plates (5 mm) separated by a fluid layer (100 mm) and a pairs of axially aligned transducers, performing the energy transfer and frequency modulated digital data. The system was able to transfer data at a rate of 19200 bps and simultaneously a transfer of energy of 66 mW, with this energy it was possible to feed the inside block module and a pressure and temperature sensor. During the tests, it was verified that 5.5 per cent of the energy applied to the channel was used, and it a bit error rate down to of 5 per cent was reached in a test with 2 h and 30 min of duration, using the multi-layered acoustic. The automatic carrier control system worked as expected and allowed one to reduce energy consumption in 53 per cent. The automatic gain control allowed one to reduce the error rate in 50 per cent. These control systems prove the feasibility of the proposed system and further show the usefulness of the system in scenarios that are subject to variations in the acoustic characteristics of the channel.

To support the growing global demand for energy, new sustainable solutions are needed both economically and environmentally. Thermoelectric waste heat recovery and energy harvesting could contribute by increasing industrial process efficiency, as well as powering stand-alone devices, microgenerators, and small body appliances.The structural complexity of quaternary chalcogenide materials provides an opportunity for engineering defects and disorder, to modify and possibly improve specific properties. Cu2ZnSnS4 (CZTS, often kesterite), valued for the abundance and non-toxicity of the raw materials, seems particularly suited to explore these possibilities, as it presents several structural defects and polymorphic phase transformations. The aim of this doctoral work is to systematically investigate the effects of structural polymorphism, disorder, and defects on the thermoelectric properties of CZTS, with particular emphasis to their physical origin. A remarkable case is the order-disorder transition of tetragonal CZTS, which is found responsible for a sharp enhancement in the Seebeck coefficient due to a flattening and degeneracy of the electronic energy bands. This effect, involving a randomization of Cu and Zn cations in certain crystallographic planes, is verified in bulk and thin film samples, and applications are proposed to exploit the reversible dependence of electronic properties on disorder. Low-temperature mechanical alloying is instead discovered stabilizing a novel polymorph of CZTS, which disordered cubic structure is studied in detail, and proposed deriving from sphalerite-ZnS. The total cation disorder in this compound provides an uncommon occurrence in thermoelectricity: a concurrent optimization of Seebeck coefficient, electrical and thermal conductivity. These findings, besides providing new and general understanding of CZTS, can cast light on profitable mechanisms to enhance the thermoelectric performance of semiconducting chalcogenides, as well as delineate alternative and fruitful applications.