acase@tulane.edu / 1 / Moses Oguntoye

Energy science is becoming an increasingly important multi-disciplinary area, for not only addressing the worldwide energy crisis, but also realizing desired power sources with advanced features for portable electronic devices and sensor networks. Very recently, based on triboelectric effect and electrostatic induction, a fundamentally new technology, triboelectric nanogenerator, has been demonstrated which shows unique merits. But so far, the main limitation for continuing optimizing their output performance is a lack of fundamental understanding of their core working mechanism. In this thesis research, we first unveil the fundamental theory and output characteristics of triboelectric nanogenerators. Then, we apply the developed theory to the TENG-based self-powered system design. We have developed the first genuine self-powered system to meet mW requirement of personal electronics. The system includes a multilayered TENG, a power management circuit with 60% total efficiency, and a low leakage energy storage device. Our power management circuit provides the total efficiency that is about two magnitudes higher than the traditional direct charging. And the total system performance is 330 times higher than the state-of-art designs. Driven by palm tapping, this power unit can provide a continuous DC electricity of 1.044 mW on average power in a regulated and managed manner that can be universally applied as a standard power source for continuously driving numerous conventional electronics, such as a thermometer, a heart rate monitor (electrocardiograph/ECG system), a pedometer, a wearable electronic watch, a scientific calculator, and a wireless radio-frequency communication system. Our study demonstrates the first power unit that utilizes widely accessible biomechanical energy source to sustainably drive a broad range of commercial mobile and wearable electronic devices. This self-charging unit is a paradigm shift towards infinite-lifetime energy sources that can never be achieved solely by batteries.

Metal - metal and to an extent metal - insulator contact or triboelectric charging are well known phenomena with good theoretical understanding of the charge exchange mechanism. However, insulator – insulator charging is not as well understood. Theoretical and experimental research has been performed that shows that the surface charge on an insulator after triboelectric charging with another insulator is rapidly dissipated with lowered atmospheric pressure. This pressure discharge is consistent with surface ions being evaporated off the surface once their vapor pressure falls below the saturation vapor pressure. A two-phase equilibrium model based on an ideal gas of singly charged ions in equilibrium with a submonolayer adsorbed film was developed to describe the pressure dependence of the surface charge on an insulator. The resulting charge density equation is an electrostatic version of the Langmuir isotherm for adsorbed surface particles, which describes well the experimental observations.

No description available.

Les crises énergétiques et environnementales nous obligent à chercher les sources d’énergies renouvelables, qui contribuent à la fois à réduire l’effet de serre et la consommation des sources traditionnelles d’énergie fossile. Récemment, un nouveau système, le nano-générateur triboélectrique (TENG), se convertit l’énergie mécanique en énergie électrique en combinant l’effet de la triboélectronique et de l’induction électrostatique. TENG montre comme un outil alternatif et prometteur pour la récupération des énergie s renouvelables. Pour réaliser des matériaux plus performants, la plupart des recherches s’appuie sur le choix des différents types des céramiques ou charges conductrices, de taux de charge et de nouvelle structure, l’effet de l’interface entre charge, ainsi que la taille des charges, matrice a été très peu étudié. Donc, l’objectif de cette thèse consiste à étudier les effets de taille des charges, de l’interface entre charge-matrice et de la polarisation sur les performances électriques du TENG et les nano-générateurs du type piézo/tribohybride (P-TENG). Tout d’abord, un TENG fonctionnant sous la mode de contact-séparation avec la motion de l’accélération/décélération a été utilisé dans notre expérimentation et les équations progressives du type du second ordre polynomial ont été choisi pour l’ajustement des courbes. Différents paramètres cinétiques comme distance entre deux électrodes, fréquence de déplacement, pression de contact et temp du repos du TENG basés sur les conditions expérimentales ont été étudiés dans le chapitre 2 afin de comprendre leur contributions sur les performances des sorties électriques. Deuxièmement, deux différentes tailles (BT-70, BT-500) des nanoparticules de BaTiO3 sont considérées et utilisées pour préparer des composites di électriques BaTiO3/PDMS et BaTiO3-MWCNT/PDMS dans le chapitre 3. Les propriétés di électriques de tous ces composites ont été caractérisées et le déplacement électrique entre les particules et le polymère a été analysé théoriquement. En plus, l’effet synergique de MWCNT, de nitrure de bore (BN) et de noir de carbone (CB) avec BaTiO3 dans BaTiO3-70-MWCNT (CB, BN) / PDMS ont été comparés. Tous ces films composites fabriqués précédemment sont ensuite utilisés dans l’assemblage des dispositifs TENG dans le chapitre 4. Les performances électriques ont été mesurées pour étudier l’influence de l’interface charge-matrice et l’effet synergique des particules MWCNT (CB, BN) pour les dispositifs TENG. Les résultats de la différence potentielle surfacique induite par les effets synergiques des BaTiO3/MWCNT ont été confirmé avec les simulations COMSOL Multiphysics. En outre, dans le chapitre 5 les films composites contenant des particules de BaTiO3 sont polarisés pour étudier les effets piézoélectriques et triboélectriques couplés pour P-TENG. Les effets des différents paramètres de polarisation, tels que la direction de polarisation, la température, le ratio massique du BaTiO3, le champ électrique et la taille des BaTiO3 sur les performances de P-TENG ont été discutées. Enfin, les conclusions générales sont présentées et certains ou quelques perspectives sont proposées pour le futur. / The increasing energy crisis and environmental pollution stimulate the development of renewable energies, which contribute to reducing the greenhouse effect and the consumption of traditional fossil fuels. As a new type of renewable energy harvesting system, triboelectric nanogenerator (TENG) converts mechanical energy to electrical energy by coupling the effect of triboelectrification and electrostatic induction. TENG has been proved to be an alternative and promising approach to harvest renewable energy in recent years. For the dielectric material candidates, more attention has been paid to choosing different types of ceramic or conductive fillers, filler loading and surface structure design, rather than considering the filler-matrix interface effect. Thus, it is desired to clarify the effect of filler size and fillermatrix interface on the performance of compositebased TENGs. This work aims to research the influence of filler size, filler-matrix interface, and polarization on the output performance of TENG and piezo/tribo-hybrid nanogenerator (P-TENG). Firstly, the contact-separation mode TENG with acceleration/deceleration motion is utilized in our experiments. The piecewise second-order polynomial fitting is chosen for the motion process curve fitting. Various kinematic parameters including gap distance, motion frequency, contact pressure, and pause time of TENG are studied theoretically based on the experiment conditions in chapter 2, to understand their contributions to the electrical output performance. Secondly, in chapter 3, BaTiO3 nanoparticles with two different sizes (BT-70, BT-500) are considered and utilized to prepare BaTiO3/PDMS and BaTiO3-MWCNT/PDMS dielectric composites. The dielectric properties of all composites are characterized, and the electric displacement between particle and polymer are theoretically analyzed. Moreover, the synergistic effect of MWCNT, boron nitride (BN) and carbon black (CB) with BaTiO3 in BaTiO3-70-MWCNT(CB, BN)/PDMS are compared. Then, all composite films fabricated were further utilized to assemble TENG devices in chapter 4. The output voltage, current, and charges densities of TENGs are evaluated to investigate the influence of fillermatrix interface and synergistic effect of MWCNT (CB, BN) particles on the output performance of TENG devices. COMSOL Multiphysics simulation are performed to further confirm the surface potential difference introduced by the synergistic effects of BaTiO3/MWCNTs. Furthermore, the composite films with BaTiO3 particles are polarized to further explore the interaction of piezoelectric and triboelectric effects for P-TENG in chapter 5. Influences of different polarization parameters, such as polarization direction, poling temperature, BaTiO3 mass ratio, poling electric field and BaTiO3 sizes, on the output performance of the PTENG have been discussed. Finally, general conclusions are presented and perspectives are proposed for the future work.

No description available.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / A novel concept using the cockpit voice recorder (CVR) as a structural vibration recording device, to aid in structural health monitoring of commercial and military aircraft, is outlined. The unused cables in the CVR wiring harness act as “latent transducers” that respond to structural vibrations, generating vibration signals, which the CVR records. Postprocessing of such data can provide clues to problem areas or changes in the signature of the aircraft. The standards which the CVR must meet to qualify as a instrumentation-quality recorder are discussed and the steps required to assure compliance are outlined.

We are surrounded by enormous amounts of ambient mechanical energy that goes to waste such as rain drops, human footfalls, air flow, ocean waves, just to name a few. If such otherwise wasted mechanical energy can be effective converted into electricity, self-powered electronics are very likely to be realized, which can address the limitations of traditional power supplies in many cases, such as wireless sensor networks. Here in this work, two types of energy-harvesting nanogenerators (NGs) based were studied. For piezoelectric nanogenerators, zinc oxide (ZnO) nanowires (NWs) were used as building blocks to develop integrated NGs based on a number of ZnO NWs instead of a single NW. Two types of integrated NGs were developed, which consist of lateral NW arrays and vertical NW arrays. The electric output power was substantially enhanced compared to the design with a single NW. For triboelectric nanogenerators, triboelectric effect was innovatively used as an effective means of harvesting mechanical energy. The operating principle can be explained by the coupling between triboelectric and electrostatic effect. Two types of operating modes were invented, i.e. contact mode and sliding mode. Triggered by commonly available ambient mechanical energy such as footfalls, the maximum output power reached up to 1.2 W. More importantly, self-powered systems were built by using the NG as a power source. It can provide real time power for up to 600 commercial LED bulbs. This research not only provides the fundamentals for NGs but also demonstrates the practicability of using the self-powered technology in our daily life.

This thesis present the fabrication of 2 types of soft wearable electrical devices, utilizing the 3D printing technique. The devices are capable to detect human heart pulse waves and sound waves for health evaluation and speech recognition.

The advent of additive manufacturing has opened up new frontiers in developing metal structures that can have complex geometries, composite structures made of dissimilar metals, and metal structures with embedded sensing and actuation capabilities. These types of structures are possible with ultrasonic additive manufacturing (UAM); a novel manufacturing technology that combines additive manufacturing through the ultrasonic welding of thin metal foils with computer numerical control (CNC) milling. However, the process suffers from a critical limitation, i.e., a range of build heights within which bonding between a foil and the substrate cannot be originated. <br>This work has two research objectives, the first is a fundamental understanding of the complex dynamic interaction between the substrate and ultrasonic horn, or sonotrode. Specifically, it focuses on the effects that specific modes of vibration have on the dynamic response of the substrate. The second objective is to utilize the UAM process to create metal structures with an embedded sensor that can detect contact or impact. In addressing the first objective, a semi-analytical model was developed to determine the response to three forcing descriptions that approximate the interfacial friction between the foil and substrate induced by sonotrode compression and excitation. Several observations can be seen in the results: as the height increases the dominant modes of vibration change, the modes of vibration excited also change during a single weld cycle as the sonotrode travels across the length of the substrate, and finally the three forcing models do not have a significant impact on the substrate response trends with height and during the weld cycle. <br>In addressing the second objective, three prototypes were created by embedding a triboelectric nanogenerator (TENG) sensor within an AL3003 metal-matrix. TENGs utilize contact electrification between surfaces of dissimilar materials, typically polymers, combined with electrostatic induction to generate electrical energy from a mechanical excitation. The sensors demonstrate a discernible response over a 1-5 Hz frequency range. In addition, the sensors have a linear relationship between output voltage and a mechanically applied load, and have the ability to sense contact through both touch and due to an impacting object.