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

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

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

IEEE Access special section editorial: energy harvesting technologies for wearable and implantable devices

Implantable and wearable electronic devices can improve the quality of life as well as the life expectancy of many chronically ill patients, provided that certain biological signs can be accurately monitored. Thanks to advancements in packaging and nanofabrication, it is now possible to embed various microelectronic and micromechanical sensors such as gyroscopes, accelerometers, and image sensors into a small area on a flexible substrate and at a relatively low cost. Furthermore, these devices have been integrated with wireless communication technologies to enable the transmission of both signals and energy. However, to ensure that these devices can truly improve a patient’s quality of life, new preventative, diagnostic, and therapeutic devices that can provide hassle-free, long-term, continuous monitoring will need to be developed, which must rely on novel energy harvesting solutions that are non-obstructive to its wearer. So far, research in the field has focused on materials, new processing techniques, and one-off devices. However, existing progress is not sufficient for future electronic devices to be useful in any new application, and a great demand exists toward scaling up the research toward circuits and systems. Few interesting developments in this direction indicate that special attention should be given toward the design, simulation, and modeling of energy harvesting techniques while keeping system integration and power management in consideration

Piezoelectric energy harvesting for self-powered wearable upper limb applications

Wearable devices can be used for monitoring vital physical and physiological signs remotely, as well as for interacting with computers. Widespread adoption of wearables is somewhat hindered by the duration time they can be used without re‐recharging. To ensure uninterrupted operation, these devices need a constant and battery‐less energy supply. Scavenging energy from the wearable's surroundings is, therefore, an essential step towards achieving genuinely autonomous and self‐powered devices. While energy harvesting technologies may not completely eliminate the battery storage unit, they can ensure a maximum duration of use. Piezoelectric energy harvesting is a promising and efficient technique to generate electricity for powering wearable devices in response to body movements. Consequently, we systematically survey the range of technologies used for scavenging energy from the human body, with a particular focus on the upper‐limb area. According to our review and in comparison to other upper limb locations, highest power densities can be achieved from piezoelectric transducers located on the wrist. For short and fast battery charging needs, we therefore review the range of materials, architectures and devices used to scavenge energy from these upper‐limb areas. We provide comparisons as well as recommendations and possible future directions for harvesting energy using this promising technique

Understanding the effect of porosity on the polarisation-field response of ferroelectric materials

This paper combines experimental and modelling studies to provide a detailed examination of the influence of porosity volume fraction and morphology on the polarisation-electric field response of ferroelectric materials. The broadening of the electric field distribution and a decrease in the electric field experienced by the ferroelectric ceramic medium due to the presence of low-permittivity pores is examined and its implications on the shape of the hysteresis loop, remnant polarisation and coercive field is discussed. The variation of coercive field with porosity level is seen to be complex and is attributed to two competing mechanisms where at high porosity levels the influence of the broadening of the electric field distribution dominates, while at low porosity levels an increase in the compliance of the matrix is more important. This new approach to understanding these materials enables the seemingly conflicting observations in the existing literature to be clarified and provides an effective approach to interpret the influence of pore fraction and morphology on the polarisation behaviour of ferroelectrics. Such information provides new insights in the interpretation of the physical properties of porous ferroelectric materials to inform future effort in the design of ferroelectric materials for piezoelectric sensor, actuator, energy harvesting, and transducer applications