Flexible PVDF-TrFE Nanocomposites with Ag-decorated BCZT Heterostructures for Piezoelectric Nanogenerator Applications

Flexible piezoelectric nanogenerators are playing an important role in delivering power to next-generation wearable electronic devices due to their high-power density and potential to create self-powered sensors for the Internet of Things. Among the range of available piezoelectric materials, poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)-based piezoelectric composites exhibit significant potential for flexible piezoelectric nanogenerator applications. However, the high electric fields that are required for poling cannot be readily applied to polymer composites containing piezoelectric fillers due to the high permittivity contrast between the filler and matrix, which reduces the dielectric strength. In this paper, novel Ag-decorated BCZT heterostructures were synthesized via a photoreduction method, which were introduced at a low level (3 wt %) into the matrix of PVDF-TrFE to fabricate piezoelectric composite films. The effect of Ag nanoparticle loading content on the dielectric, ferroelectric, and piezoelectric properties was investigated in detail, where a maximum piezoelectric energy-harvesting figure of merit of 5.68 × 10-12 m2/N was obtained in a 0.04Ag-BCZT NWs/PVDF-TrFE composite film, where 0.04 represents the concentration of the AgNO3 solution. Modeling showed that an optimum performance was achieved by tailoring the fraction and distribution of the conductive silver nanoparticles to achieve a careful balance between generating electric field concentrations to increase the level of polarization, while not degrading the dielectric strength. This work therefore provides a strategy for the design and manufacture of highly polarized piezoelectric composite films for piezoelectric nanogenerator applications.</p

Piezoelectric Energy Harvester Technologies: Synthesis, Mechanisms, and Multifunctional Applications.

Piezoelectric energy harvesters have gained significant attention in recent years due to their ability to convert ambient mechanical vibrations into electrical energy, which opens up new possibilities for environmental monitoring, asset tracking, portable technologies and powering remote "Internet of Things (IoT)" nodes and sensors. This review explores various aspects of piezoelectric energy harvesters, discussing the structural designs and fabrication techniques including inorganic-based energy harvesters (i.e., piezoelectric ceramics and ZnO nanostructures) and organic-based energy harvesters (i.e., polyvinylidene difluoride (PVDF) and its copolymers). The factors affecting the performance and several strategies to improve the efficiency of devices have been also explored. In addition, this review also demonstrated the progress in flexible energy harvesters with integration of flexibility and stretchability for next-generation wearable technologies used for body motion and health monitoring devices. The applications of the above devices to harvest various forms of mechanical energy are explored, as well as the discussion on perspectives and challenges in this field

3D-Printed Flexible PVDF-TrFE Composites with Aligned BCZT Nanowires and Interdigital Electrodes for Piezoelectric Nanogenerator Applications

Piezoelectric nanogenerators based on piezoelectric nanocomposites have attracted much interest in recent decades owing to their excellent piezoelectric properties and application in self-powered systems and wearable sensors. As a promising piezoelectric ceramic filler in composite-based generators, one-dimensional (1D) piezoelectric nanowires were filled into a polymer matrix to enhance its dielectric and piezoelectric properties. In this paper, flexible PVDF-TrFE composite films containing highly aligned Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) nanowires (NWs) have been manufactured via a direct-ink writing method. The effect of BCZT NW content on the dielectric, ferroelectric, and piezoelectric properties was investigated using multiphysics modeling and detailed experiments. An optimum composite composition was discovered, and the piezoelectric composite film with 15 wt % BCZT NWs possessed the highest energy harvesting figure of merit of 5.3 × 10-12 m2/N. Interdigital electrodes were combined with the composite to fabricate a patterned piezoelectric nanogenerator, where the piezoelectric nanogenerator can produce an open-circuit output voltage of 17 V, and the maximum output power density could reach 5.6 μW/cm2. This work provides opportunities for the optimization and fabrication of piezoelectric materials for energy-harvesting and sensing applications.</p

3D-Printed Flexible PVDF-TrFE Composites with Aligned BCZT Nanowires and Interdigital Electrodes for Piezoelectric Nanogenerator Applications

Piezoelectric nanogenerators based on piezoelectric nanocomposites have attracted much interest in recent decades owing to their excellent piezoelectric properties and application in self-powered systems and wearable sensors. As a promising piezoelectric ceramic filler in composite-based generators, one-dimensional (1D) piezoelectric nanowires were filled into a polymer matrix to enhance its dielectric and piezoelectric properties. In this paper, flexible PVDF-TrFE composite films containing highly aligned Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) nanowires (NWs) have been manufactured via a direct-ink writing method. The effect of BCZT NW content on the dielectric, ferroelectric, and piezoelectric properties was investigated using multiphysics modeling and detailed experiments. An optimum composite composition was discovered, and the piezoelectric composite film with 15 wt % BCZT NWs possessed the highest energy harvesting figure of merit of 5.3 × 10-12 m2/N. Interdigital electrodes were combined with the composite to fabricate a patterned piezoelectric nanogenerator, where the piezoelectric nanogenerator can produce an open-circuit output voltage of 17 V, and the maximum output power density could reach 5.6 μW/cm2. This work provides opportunities for the optimization and fabrication of piezoelectric materials for energy-harvesting and sensing applications.</p

Recent Structure development of poly(vinylidene fluoride)-based piezoelectric nanogenerator for self-powered sensor

As the internet of things (IoT) era approaches, various sensors, and wireless electronic devices such as smartphones, smart watches, and earphones are emerging. As the types and functions of electronics are diversified, the energy consumption of electronics increases, which causes battery charging and maintenance issues. The piezoelectric nanogenerator (PENG) received great attention as an alternative to solving the energy issues of future small electronics. In particular, polyvinylidene fluoride (PVDF) piezoelectric polymer-based PENGs are strong potential candidate with robust mechanical properties and a high piezoelectric coefficient. In this review, we summarize the recent significant advances of the development of PVDF-based PENGs for self-powered energy-harvesting systems. We discuss the piezoelectric properties of the various structures of PVDF-based PENGs such as thin film, microstructure, nanostructure, and nanocomposite. © 2020 by the authors.1

Polymeric PVDF Fibers for Piezoelectric Applications in Energy Harvesting

This work focuses on developing and characterizing the piezoelectric response of Cerium doped Polyvinylidene Fluoride (PVDF) fine fibers and the effects of dopants and alignment on the formation of the β-phase and consequently on the piezoelectric performance. Six sets of fiber mats were prepared varying the concentration (2.5–7.5wt%) of Cerium (III) Nitrate-Hexahydrate and Ammonium-Cerium (IV) Sulfate-Dihydrate. Fiber mats were developed using the Forcespinning® technique and the angular velocity and dopant concentration were adjusted to obtain a synergy between fiber yield and fiber diameter. Fourier Transform Infrared Spectroscopy showed a significant enhancement in the PVDF β-phase and inhibition of the non-polar α-phase. The doping effect of the cerium complexes shows a small effect on the piezoelectric response, with the PVDF Cerium-Sulfate fibers producing 7 to 8V; whereas the pure PVDF fibers’ response ranged between 5 to 7V. Fibers doped with 5wt% Cerium-Sulfate showed the best fiber morphology and had the highest yield of production. Addition of graphene demonstrated increased in sensitivity for the fibers, while the addition of PPy helped in increasing the charge/discharge rate for the fibers’ voltage response. The effect of fiber alignment proved beneficial by increasing the β-phase formation of the fibers, reducing fiber diameter, and thus producing higher voltage response, 9.20–11 V for 5wt% Cerium-Sulfate

A Flexible Sandwich Nanogenerator for Harvesting Piezoelectric Potential from Single Crystalline Zinc Oxide Nanowires

High-quality single crystalline zinc oxide nanowires were grown on silver and gold coated plastic substrates for the fabrication of a sandwich-like nanogenerator using the aqueous chemical growth method. The applicability of this configuration as a nanogenerator is demonstrated by studying the harvested electrical output under mechanical deformation. Three different configurations were fabricated and utilized for harvesting piezoelectric potential by applying an external force. The maximum resulting output open circuit voltage and short circuit current were 2.4 V and 152.2 μA, respectively. The comparison between the different configurations indicates that more piezoelectric potential can be harvested by using two arrays of ZnO NWs placed face-to-face than by using a single nanowire configuration. In addition, the use of a piezoelectric polymer will enhance the amount of generated piezoelectric potential. The obtained results from different configurations of zinc oxide nanowire nanogenerators offer a cost-effective, flexible, long term stable nanogenerator for promising application. The principle of the sandwich nanogenerator demonstrated a new idea for novel self-powering nanotechnology that harvests electricity from the environment for applications such as portable electronics

Electrospinning piezoelectric fibers for biocompatible devices

The field of nanotechnology has been gaining great success due to its potential in developing new generations of nanoscale materials with unprecedented properties and enhanced biological responses. This is particularly exciting using nanofibers, as their mechanical and topographic characteristics can approach those found in naturally occurring biological materials. Electrospinning is a key technique to manufacture ultrafine fibers and fiber meshes with multifunctional features, such as piezoelectricity, to be available on a smaller length scale, thus comparable to subcellular scale, which makes their use increasingly appealing for biomedical applications. These include biocompatible fiber-based devices as smart scaffolds, biosensors, energy harvesters, and nanogenerators for the human body. This paper provides a comprehensive review of current studies focused on the fabrication of ultrafine polymeric and ceramic piezoelectric fibers specifically designed for, or with the potential to be translated toward, biomedical applications. It provides an applicative and technical overview of the biocompatible piezoelectric fibers, with actual and potential applications, an understanding of the electrospinning process, and the properties of nanostructured fibrous materials, including the available modeling approaches. Ultimately, this review aims at enabling a future vision on the impact of these nanomaterials as stimuli-responsive devices in the human body

From synthesis to application: High-quality flexible piezoelectric sensors fabricated from tetragonal BaTiO3/ P(VDF-TrFE) composites:High-quality flexible piezoelectric sensors fabricated from tetragonal BaTiO₃/ P(VDF-TrFE) composites

In this work, a simple process for fabrication of piezoelectric BaTiO3 /P(VDFTrFE) composites from synthesis to its application as a wearable piezoelectric sensor is presented. Addition of 10 wt% synthesized tetragonal BaTiO3 particles (200 nm in diameter) enhanced the mechanical and piezoelectric properties of P(VDF-TrFE) better than commercial cubic phase particles (&lt;100 nm in diameter). Although P(VDF-TrFE) and tetragonal BaTiO3 have opposite piezoelectric coefficients, BaTiO3 improved the performance of the final piezoelectric sensor by modifying the distribution of stress in the P(VDF-TrFE) matrix, reducing the viscosity, and causing the mechanical reinforcement of the composite films. This requires the uniform distribution of particles in the polymer matrix, which was succeeded by prior surface modification of the particles. Inverse piezoelectric properties of BaTiO3 /P(VDF-TrFE) composites were enhanced by obtaining a higher polarization (Pr = 6.18 µC/cm2) and dielectric constant value (εr = 30.3) compared to pure P(VDF-TrFE)(Pr = 4.23 µC/cm2, εr = 8.8). Furthermore, the ferroelectric and switching behavior in the composites happened at lower electric fields. With respect to direct piezoelectric properties, the voltage coefficient of this composite is 30% higher than the pure P(VDF-TrFE). By fabricating simple wearable piezoelectric sensors for finger joint movement detection, the composite device showed an enhancement in output voltage (2.1 times), power (4.6 times), and sensitivity (1.6 times) in comparison to the pure P(VDF-TrFE) sensor. The composite sensor with a sensitivity of 10.16 mV/N, is able to produce a maximum peak-to-peak output voltage of 400 mV by bending the finger without the need for any amplification or post-processing.</p

Wearable nanocomposite textile-based piezoelectric and triboelectric nanogenerators: progress and perspectives

In recent years, the widespread adoption of next-generation wearable electronics has been facilitated by the integration of advanced nanogenerator technology with conventional textiles. This integration has led to the development of textile-based nanogenerators (t-NGs), which hold tremendous potential for harvesting mechanical energy from the surrounding environment and serving as power sources for self-powered electronics. Textile structures are inherently flexible, making them well-suited for wearable applications. However, their electrical performance as nanogenerators is significantly limited when used without any modifications. To address this limitation and enhance the electrical performance of textile-based nanogenerators, nanocomposite textiles have been extensively utilized for fabricating advanced nanogenerators. This critical review focuses on the recent progress in wearable nanocomposite textiles-based piezoelectric and triboelectric nanogenerators. The review covers the fundamentals of piezoelectricity and triboelectricity, the working principles of nanogenerators, and the selection of materials. Furthermore, it provides a detailed discussion of nanocomposite textiles in various forms, such as fibers or yarns, fabrics, and electrospun nanofibrous webs, which are employed in piezoelectric and triboelectric nanogenerators. The review also highlights the challenges associated with their implementation and outlines the prospects of textile-based nanogenerators. It can be concluded that nanocomposite textile based piezoelectric and triboelectric nanogenerators exhibit better electrical output and mechanical strength compared to conventional textile based nanogenerators. Nanocomposite electrospun web based piezoelectric nanogenerators exhibit higher piezoelectric output compared with nanocomposite fibre/yarn or fabric based piezoelectric nanogenerators. This is because an in-situ poling takes place in electrospinning unlike with fibre or fabric based piezoelectric nanogenerators. Nanocomposite electrospun web based triboelectric nanogenerators also show better triboelectric output compared to the fibre or fabric-based equivalents. This is due to the higher contact area developed with electrospun nanocomposite webs compared to the fibre or fabric cases. Overall, it can be concluded that while nanocomposite construction can boost output and durability of textile based nanogenerators, more research is required to bring output, stability and durability up to the levels achievable with non-textile based devices