Advanced Nanoelectromechanical Systems for Next Generation Energy Harvesting

The ever-increasing desire to produce portable, mobile and self-powered wireless micro-/nano systems (MNSs) with extended lifetimes has lead to the significant advancement in the area of mechanical energy harvesting over the last few years and it has been possible not only because has nanotechnology evolved as a powerful tool for the manipulation of matter on an atomic, molecular, and supramolecular scale, but also different micro-/nano fabrication techniques have enabled researchers and scientists to create, visualize, analyse and manipulate nano-structures, as well as to probe their nano-chemistry, nano-mechanics and other properties within the systems. The dissertation first discusses briefly about energy harvesting technologies for self-powered MNSs, for example a wireless aircraft structural health monitoring (SHM) system, with a particular focus on piezoelectric nanogenerators (PENG) and triboelectric nanogenerators (TENG) as they are the most promising approaches for converting ambient tiny mechanical energy into electrical energy efficiently and effectively and then it analyzes the theoretical and experimental methodologies for efficient energy harvesting using PENG, TENG and hybrid devices. The piezoelectric property intertwined with the semiconducting behaviour of different ZnO nanostructures has made them ideal candidate for piezoelectric energy harvesting, also intensive and state-of-the-art research has been going on to enhance the performance of the PENG devices based on 1D and 2D ZnO nanostructures. In this work, a high performance and consolidated PENG device based on the integration of ZnO nanowires and nanoplates on the same substrate has been demonstrated, that produces an output electrical power of 8.4 µW/cm2 at the matched load of 10MΩ that manifests their ability for powering up different MNSs. Since hybrid nanogenerators (HNG) integrate different types of harvesters in a single unit, where several energy sources can be leveraged either simultaneously or individually, in the next part of this work, a HNG device integrating PENG and TENG components has been designed, fabricated and characterized where PENG and TENG parts mutually enhance the performance of each other resulting an instantaneous peak power density of 1.864mW/cm2 and subsequently the device has been used to charge several commercial capacitors to corroborate their potential for aircraft SHM applications. Moreover, the hybrid device exhibits strong potential for wearable electronics as it can harvest energy from human walking and normal hand movements. However, successful implementation of self-powered electronics, such as a wireless aircraft SHM depends not only on the performance of individual parts but also on components integration within the system, where each device/system node within the network consists of a low-power microcontroller unit, high-performance data-processing/storage units, a wireless signal transceiver, ultrasensitive sensors based on a micro-/nano electro-mechanical system, and most importantly the embedded powering units. This dissertation aims to deepen the understanding of the different energy harvesting methods utilizing the knowledge of nanoscale phenomena and nanofabrication tools along with the associated prospects and challenges and thus, this research in the field of energy harvesting using advanced nano electro-mechanical systems could have a substantial impact on many areas, ranging from the fundamental study of new nanomaterial properties and different effects in nanostructures to diverse applications

Plasma engineering of microstructured piezo – Triboelectric hybrid nanogenerators for wide bandwidth vibration energy harvesting

We introduce herein the advanced application of low-pressure plasma procedures for the development of piezo and triboelectric mode I hybrid nanogenerators. Thus, plasma assisted deposition and functionalization methods are presented as key enabling technologies for the nanoscale design of ZnO polycrystalline shells, the formation of conducting metallic cores in core@shell nanowires, and for the solventless surface modification of polymeric coatings and matrixes. We show how the perfluorinated chains grafting of polydimethylsiloxane (PDMS) provides a reliable approach to increase the hydrophobicity and surface charges at the same time that keeping the PDMS mechanical properties. In this way, we produce efficient Ag/ZnO convoluted piezoelectric nanogenerators supported on flexible substrates and embedded in PDMS compatible with a contact–separation triboelectric architecture. Factors like crystalline texture, ZnO thickness, nanowires aspect ratio, and surface chemical modification of the PDMS are explored to optimize the power output of the nanogenerators aimed for harvesting from low-frequency vibrations. Just by manual triggering, the hybrid device can charge a capacitor to switch on an array of color LEDs. Outstandingly, this simple three-layer architecture allows for harvesting vibration energy in a wide bandwidth, thus, we show the performance characteristics for frequencies between 1 Hz and 50 Hz and demonstrate the successful activation of the system up to ca. 800 Hz.EMERGIA Junta de Andalucía programUniversity of Seville the VI PPIT-USICMS and the CITIUS from the University of Sevill

Large-scale Lateral Nanowire Arrays Nanogenerators

In a method of making a generating device, a plurality of spaced apart elongated seed members are deposited onto a surface of a flexible non-conductive substrate. An elongated conductive layer is applied to a top surface and a first side of each seed member, thereby leaving an exposed second side opposite the first side. A plurality of elongated piezoelectric nanostructures is grown laterally from the second side of each seed layer. A second conductive material is deposited onto the substrate adjacent each elongated first conductive layer so as to be coupled the distal end of each of the plurality of elongated piezoelectric nanostructures. The second conductive material is selected so as to form a Schottky barrier between the second conductive material and the distal end of each of the plurality of elongated piezoelectric nanostructures and so as to form an electrical contact with the first conductive layer.Georgia Tech Research Corporatio

Hybrid cell for harvesting multiple-type energies

An abundance of energy in our environment exists in the form of light, thermal, mechanical (e.g., vibration, sonic waves, wind, and hydraulic), magnetic, chemical, and biological. Harvesting these forms of energy is of critical importance for solving long-term energy needs and the sustainable development of the planet. However, conversion cells for harvesting solar energy and mechanical energy are usually independent entities that are designed and built following distinct physical principles. The effective and complementary use of such energy resources whenever and wherever one or all of them are available demands the development of innovative approaches for the conjunctional harvesting of multiple types of energy using an integrated structure/material. By combining solar and mechanical energy-harvesting modules into a single package for higher energy conversion efficiency and a more effective energy recovery process, the research has designed and demonstrated a hybrid cell for harvesting solar and mechanical energy. The results of the research show that we can fully utilize the energy available from our living environment by developing a technology that harvests multiple forms of both solar and mechanical energy 24 hours a day. As the proposed research represents a breakthrough in the innovation of energy harvesting, it should pave the way toward building a new field called "multi-type hybrid" energy harvesting.PhDCommittee Chair: Zhong Lin Wang; Committee Member: Christopher Summers; Committee Member: Gee-Kung Chang; Committee Member: Jud Ready; Committee Member: Zhiqun Li

Enhanced Piezoelectric Behavior of PVDF Nanocomposite by AC Dielectrophoresis Alignment of ZnO Nanowires

In contrast to commercial piezoelectric ceramics, lead-free materials such as ZnO and a polymer matrix are proper candidates for use in ecofriendly applications. In this article, the authors represent a technique using ZnO nanowires with a polyvinylidene fluoride (PVDF) matrix in a piezoelectric polymer composite. By aligning the nanowires in the matrix in a desired direction by AC dielectrophoresis, the piezoelectric behavior was enhanced. The dielectric constant of the composite was improved by increasing the concentration of the ZnO nanowires as well. Specifically, the resulting dielectric constant shows an improvement of 400% with aligned ZnO nanowires by increasing the poling effect compared to that of a randomly oriented nanowire composite without a poling process

Hybrid Structural Composites with Energy Harvesting Capabilities

Hybrid materials have received significant interest due to the potential enhancements they provide over traditional materials such as sensing, actuating, energy scavenging, thermal management, and vibration damping. While traditional materials can be utilized for either one of these functions or loadbearing, the hybrid materials are superior as they allow combination of a wide array of functionalities whilst being suitable for load-bearing purposes. The goal of this thesis is to elucidate the synergistic effects of hybridization of two piezoelectric materials; zinc oxide nanowires (ZnO NWs) and thin film of lead zirconium titanate (PZT) on the mechanical and energy harvesting of beams made from plain-woven carbon fiber reinforced epoxy composites (CFRPs). ZnO NWs have, by contrast, displayed great promises. While not only being a very strong piezoelectric material, it enhanced the mechanical and dynamic properties of the composite due to the increased surface area and mechanical interlocking. However, the aspect of energy scavenging is somewhat limited due to the weak piezoelectrical effects of ZnO nanowires. In this thesis, the prospects of ZnO NWs are exploited further to improve both their production processes and piezoelectric performance. Combining ZnO NWs grown on carbon fibers combined with other piezoelectrical materials has not yet been implemented but appears to be encouraging. This is the focus of this thesis. Despite that the composite comprising the combination of the two piezoelectric materials showed a minor drop in tensile strength and damping characteristics, the substantial gain in both stiffness (25.8 % increase compared to plain composite) and the electrical power gain (733.94 % more than that for ZnO NWs) is very promising for future application of the hybrid material into real engineering problems. A comprehensive study utilizing available commercial finite element software to simulate and foresee the behavior of hybrid materials was also carried out. The simulations agreed qualitatively with the experimental observations and explanations of the discrepancies between the model and experiment setup were discussed. Despite the preliminary promising results, more work is necessary to exploit the full potential of these material by optimizing the design of the energy harvesting devices and establishing more feasible models that treat the electromechanical coupling of these multifunctional hybrid composites more realistically

Some experimental investigation on effect of light and vibration on nano coated piezo for energy harvesting

PZT is a promising piezoelectric ceramic material which has a wide range of applications in a variety of fields such as acoustic sensors and transducers, electrical switches, medical instrumentation, artificial sensitive skin in robotics, automotive detection on roads, nondestructive testing , structural health monitoring and as a biocompatible material. In this research a cantilever based multi energy harvester was developed to maximize the power output of PZT sensor. Nano mixtures containing graphene, ferrofluid nanoparticle (FNP) and ZnO nano particles were used to enhance the piezoelectric and photovoltaic output of the sensor. The samples were tested under different energy conditions to observe the behavior of nano coated PZT film under multi energyconditions (vibration and light). Composition of the ZnO and FNP was changed by weight in order to achieve the optimal composition of the nano mixture. Light energy, vibration energy, combined effect of light and vibration energy were used to explore the behavior of the sensor. The sensor with 1% Epoxy, 40% ZnO and 59% FNP achieved a maximum power output of 9404.28 μWatt/sec with vibration only from 65-400Hz. The sensor with 1% Epoxy, 5% graphene 40% ZnO and 54% FNP achieved a maximum power output of 13279.23 μWatt/sec when under the combined effect of light (3780 lumens) and vibrationenergy (65-400Hz). This was nearly 3 times more power output than the pure PZT sensor