Energy harvesting from water flow by using piezoelectric materials

As a promising energy-harvesting technique, an increasing number of researchers seek to exploit the piezoelectric effect to power electronic devices by harvesting the energy associated with water flow. In this emerging field, a variety of research themes attract interest for investigation; these include selection of the excitation mechanism, oscillation structure, piezoelectric material, power management interface circuit, and application. Since there has been no comprehensive review to date with respect to the harvesting of water flow using piezoelectric materials, herein relevant work in the last 25 years is reviewed. To ensure that key aspects of the water-flow energy harvester are overviewed, they are discussed in the context of energy-flow theory, which includes the three stages of energy extraction, energy conversion, and energy transfer. The development of each energy-flow process is reviewed in detail and combined with meta-analysis of the published literature. Correlations between the harvesting processes and their contribution to the overall energy-harvesting performance are illustrated, and directions for future research are also proposed. In this review, a comprehensive understanding of water-flow piezoelectric energy harvesting is provided and it is aimed to guide future research and the development of piezoelectric harvesters for water-flow-powered devices is promoted

Control of electro-chemical processes using energy harvesting materials and devices

Energy harvesting is a topic of intense interest that aims to convert ambient forms of energy such as mechanical motion, light and heat, which are otherwise wasted, into useful energy. In many cases the energy harvester or nanogenerator converts motion, heat or light into electrical energy, which is subsequently rectified and stored within capacitors for applications such as wireless and self-powered sensors or low-power electronics. This review covers the new and emerging area that aims to directly couple energy harvesting materials and devices with electro-chemical systems. The harvesting approaches to be covered include pyroelectric, piezoelectric, triboelectric, flexoelectric, thermoelectric and photovoltaic effects. These are used to influence a variety of electro-chemical systems such as applications related to water splitting, catalysis, corrosion protection, degradation of pollutants, disinfection of bacteria and material synthesis. Comparisons are made between the range harvesting approaches and the modes of operation are described. Future directions for the development of electro-chemical harvesting systems are highlighted and the potential for new applications and hybrid approaches are discussed

Piezoelectric performance of PZT-based materials with aligned porosity::experiment and modelling

A new micromechanical model is proposed to analyse the piezoelectric properties of freeze-cast porous composite materials based on a ferroelectric lead zirconate titanate-type (PZT) ceramics. The important influence of the composite microgeometry and the porous ceramic matrix on the piezoelectric coefficients d∗ 3j and g∗ 3j and the piezoelectric anisotropy factor d∗ 33/|d∗ 31 in the porosity range of mp = 0.2-0.6 is evaluated and discussed. The resulting piezoelectric parameters of parallel-connected freeze-cast composites with highly aligned pore channels are then compared to those of PZT-based porous materials with randomly distributed porosity. Due to the relatively large piezoelectric coefficients d∗ 33 ∼ 102 pC N-1, g∗ 33 ≈ 40-100 mV m N-1, anisotropy factor d∗ 33/|d∗ 31 ≈ 3-5 and the presence of aligned porous channels, the parallel-connected freeze-cast composite has advantages over conventional monolithic PZT-type ceramics (e.g. g 33 = 24.2 mV m N-1 and d 33/|d 31| = 2.2 in the PZT-5 ceramic) and is suitable for piezoelectric transducer, sensor, acoustic, and energy-harvesting applications.</p

Additively Manufactured Ferroelectric Particulate Composites for Antimicrobial Applications

A polarized ferroelectric material can initiate the micro-electrolysis of water molecules which leads to the formation of reactive oxygen species (ROS) in an aqueous solution resulting in selective bacteria killing. This study presents the fabrication, characterization, and antimicrobial performance of poled ferroelectric particulate composites. Barium calcium zirconate titanate (BCZT) micro-powder is synthesized by a solid-state reaction and mechanically mixed with polycaprolactone (PCL) to be subsequently fed into the 3D bioprinter for the fabrication of porous PCL-BCZT structures at four different ceramic loadings (0, 10, 20, 30 wt%). For the examination of material's capacity to handle extremely high contamination, the composites are exposed to a high inoculum of bacteria (Escherichia coli ATCC 25922) ≈70% of E. coli degradation is recorded at the end of 15 min without any external intervention. The surface selective bacterial degradation can be attributed to the generated reactive oxygen species, the large surface area of the porous samples and polymer matrix's hydrophobic nature, behavior which can be reflected in the composites with 30 wt% of BCZT loading exhibiting the best antimicrobial performance among the other state-of-the-art ferroelectrics. Overall, these results indicate that the poled composites have a great potential as antimicrobial materials and surfaces.</p

In-situ poling and structurization of piezoelectric particulate composites

Composites of lead zirconate titanate particles in an epoxy matrix are prepared in the form of 0–3 and quasi 1–3 with different ceramic volume contents from 10% to 50%. Two different processing routes are tested. Firstly a conventional dielectrophoretic structuring is used to induce a chain-like particle configuration, followed by curing the matrix and poling at a high temperature and under a high voltage. Secondly a simultaneous combination of dielectrophoresis and poling is applied at room temperature while the polymer is in the liquid state followed by subsequent curing. This new processing route is practiced in an uncured thermoset system while the polymer matrix still possess a relatively high electrical conductivity. Composites with different degrees of alignment are produced by altering the magnitude of the applied electric field. A significant improvement in piezoelectric properties of quasi 1–3 composites can be achieved by a combination of dielectrophoretic alignment of the ceramic particles and poling process. It has been observed that the degree of structuring as well as the functional properties of the in-situ structured and poled composites enhance significantly compared to those of the conventionally manufactured structured composites. Improving the alignment quality enhances the piezoelectric properties of the particulate composites.Novel Aerospace Material

Control of electro-chemical processes using energy harvesting materials and devices

A detailed overview of pyro-electric, piezo-electric, tribo-electric, flexo-electric thermo-electric and photovoltaic charge generation mechanisms which are used to control electro-chemical reactions.</p

High voltage coefficient piezoelectric materials and their applications

The piezoelectric dij coefficient is often regarded in materials science as the most important figure of merit of piezoelectric performance. For many applications, the piezoelectric gij coefficient which correlates to voltage output and sensitivity of a piezoelectric material can be considered of equal or increased importance, however is often an overlooked parameter in materials science literature. The aim of this review is to highlight the importance of this parameter and to provide insight into the mechanisms that drive a high piezoelectric voltage coefficient in single crystal, polycrystalline, and composite form. For bulk ceramics, special attention is given to tetragonal systems due to the availability of electrical and crystallographic data allowing for a clear structure-property relation. Orthorhombic and rhombohedral systems are mentioned and specific cases highlighted, however investigating structure-property relations is difficult due to the lack of crystallographic datasets. Composite materials have been the forefront of high gij piezoelectric materials over the decades and are therefore also considered in both ceramic-matrix and polymer-matrix form. An overview of applications in medical, energy, fishing and defence industries where a high gij is desirable are considered and the scientific and commercial considerations that must be made for the transition from laboratory to industry are discussed from the perspective of integrating new piezoelectric materials into sonar devices

Gesture Recognition Wristband Device with Optimised Piezoelectric Energy Harvesters

Wearable devices can be used for monitoring vital human physiological signs and for interacting with computers. Due to the limited lifetime of batteries, these devices require novel energy harvesting solutions to ensure uninterrupted and autonomous operation. We therefore developed a wearable wristband device with piezoelectric transducers, which were used for hybrid functionality. These transducers were used for both energy harvesting and sensing applications. In fact, we also demonstrate that gestures can be classified using electricity generated from these piezoelectric transducers as a result of tendon movements around the wrist. In this paper, we demonstrate how a multi-physics simulation model was used to maximize the amount of harvestable energy from these piezoelectric transducers

Thermal energy harvesting using pyroelectric-electrochemical coupling in ferroelectric materials

Recently, the coupling of ferroelectrics with electrochemical reactions has attracted increasing interest for harvesting waste heat. The change of polarisation of a ferroelectric with temperature can be used to influence chemical reactions, especially when the material is cycled near its Curie temperature. In this perspective, we introduce the principle of pyroelectric controlled electrochemical processes by harvesting waste heat energy and explore their potential electrochemical applications, such as water treatment, air purificiation and hydrogen generation. As an emerging approach for driving electrochemical reactions, the presence of thermal fluctuations and/or transient waste heat in the environment has the potential to be the primary thermal input for driving the change in polarisation of a pyroelectric to release charge for such reactions. There are a number of avenues to explore and we summarize strategies for forming multi-functional or hybrid materials and future directions such as selecting pyroelectrics with low Curie temperature (< 100 {\deg}C), improved heat conductivity, enhanced surface area or porosity, tailored microstructures and systems capable of operating over a broader temperature range

Enhancing Neural Stem Cell Stimulation with Structured Piezoelectric Composites: An In Vitro Study

Spinal cord injuries can cause permanent tissue damage with debilitating and lasting effects on patients. Electrical stimulation has been established as an effective approach for promoting neural regeneration. However, the clinical applicability of these techniques is limited by the necessity for wired connections and external power supplies, which increases risk of infection. Piezoelectric materials have the inherent ability to form electric surface potentials when subjected to a mechanical stress and can provide wireless electrical stimulation. However, current materials are not optimized for neurological applications as they are mechanically mismatched with neural tissue, and have poor biocompatibility. Further, reproducible systems for optimizing material design and stimulation paradigms have yet to be established. Here a new, advanced fabrication process to produce scalable, tuneable piezoelectric ceramic–polymer composites based on [K0.5Na0.5]NbO3 and polydimethylsiloxane is provided. It is demonstrated that these composites can be successfully utilized for the growth of neural stem cells, which are shown to survive, proliferate, retain stemness, and differentiate into their daughter populations. Neuronal differentiation appears to be preferred on poled substrates, in comparison to glass coverslips and unpoled substrates. It is shown that the composites can autonomously generate surface potentials, which opens new possibilities to study piezoelectrically induced electrical stimulation