High-performance Flexible Piezoelectric Nanogenerator Research Articles

High-performance flexible piezoelectric nanogenerator assisted by a three-phase PVDF/WS2/rGO nanocomposite

The emergence of piezoelectric nanogenerators (PENGs) presents a promising alternative to supply energy demands within the realms of portable and miniaturized devices. In this article, the role of 2D transition metal dichalcogenide tungsten sulfide (WS2) and conductive rGO sheets as filler materials inside the polyvinylidene fluoride (PVDF) matrix on piezoelectric performances has been investigated extensively. The strong electrostatic interaction between C–F and C–H monomer bonds of PVDF interacted with the large surface area of the WS2 nanosheets, increasing the electroactive polar phases and resulting in enhanced ferroelectricity in the PVDF/WS2 nanocomposite. Further, the inclusion of rGO sheets in the PVDF/WS2 composite allows mobile charge carriers to move freely through the conductive network provided by the rGO basal planes, which improves the internal polarization of the PVDF/WS2/rGO nanocomposites and increases the electrical performance of the PENGs. The PVDF/WS2/0.3rGO nanocomposite-based PENG exhibits maximum piezoresponses with ∼8.1 times enhancements in the output power density than the bare PVDF-based PENG. The mechanism behind the enhanced piezoresponses in the PVDF/WS2/rGO nanocomposites has been discussed.

Fabrication and Characterization of High Performance PVDF-based flexible piezoelectric nanogenerators using PMN-xPT (x:30, 32.5, and 35) particles

Flexible piezoelectric nanogenerators based on polyvinylidene difluoride (PVDF) and lead magnesium niobate-lead titanate Pb(Mg1/3Nb2/3)O3–PbTiO3(PMN-xPT compositions for x between 30 and 35) particles with various filler ratios from 10 to 30 vol% were fabricated through the electrospinning method. The phase and microstructural characterizations revealed that the homogenous and continuous fiber-shaped composite structure with good interfacial interaction between the PMN-PT particles and the PVDF matrix was achieved. It was found that the diameter of the neat PVDF fibers was approximately 354 nm, whereas the PVDF/PMN-35PT fibers with ceramic particle concentrations of 10, 20, and 30 vol% had average diameters of 317, 249, and 163 nm, respectively. The piezoelectric performance tests indicated that the 30 vol%PVDF/PMN-35PT nanogenerator had a 3 times greater electrical power efficiency (10.59 μW) at 20 Hz compared to that of the pure PVDF nanogenerator (3.56 μW) at 15 Hz under the same resistance load of 1 MΩ. All in all, the incorporation of PMNT-PT particles into the PVDF appears to be a good approach for the fabrication of high-performance flexible piezoelectric nanogenerator applications for biomechanical energy harvesting of devices converting the mechanical movements of organs such as cardiac and lung into electrical energy.

High performance flexible piezoelectric nanogenerator based on Bi-doped BaTiO3/polyimide composite films

ABSTRACT Piezoelectric nanogenerators (PENGs) composed of inorganic ceramic nanoparticles and polymer matrix have received extensive attention from scientific researchers. In this article, PENG based on BaTiO3-Bi/Polyimide (BTO-Bi/PI) composite thin films were prepared. The influence of the doping amount of Bi2O3 on the electrical properties of BaTiO3 and the power generation performance of composite thin films were studied in detail. BaTiO3 doped with 0.1 mol% Bi2O3 achieve optimal piezoelectric properties with d33 of 246 pC/N and d33* of 856 pm/V. The flexible BTO-Bi/PI PENG device demonstrates short-circuit current of 365 nA and open-circuit voltage of 17 V, which shows great capability of capturing mechanical energy; it also can be used as sensors under lower mechanical stress and has a wide operating temperature range.

Impact of Multi-Walled CNT Incorporation on Dielectric Properties of PVDF-BaTiO3 Nanocomposites and Their Energy Harvesting Possibilities

The current study investigated the fabrication of multi-walled carbon nanotubes (MWCNTs) adhering to Barium titanate (BaTiO3) nanoparticles and poly(vinylidene fluoride) (PVDF) nanocomposites, as well as the impact of MWCNT on the PVDF-BaTiO3 matrix in terms of dielectric constant and dielectric loss with a view to develop a high performance piezoelectric energy harvester in future. The capacity and potential of as-prepared nanocomposite films for the fabrication of high-performance flexible piezoelectric nanogenerator (PNG) were also investigated in this work. In particular, five distinct types of nanocomposites and films were synthesized: PB (bare PVDF–BaTiO3), PBC-1 (PVDF–BaTiO3-0.1 wt% CNT), PBC-2 (PVDF–BaTiO3-0.3 wt% CNT), PBC-3 (PVDF–BaTiO3-0.5 wt% CNT), and PBC-4 (PVDF–BaTiO3-1 wt% CNT). The dielectric constant and dielectric loss increased as MWCNT concentration increased. Sample PBC-3 had the optimum dielectric characteristics of all the as-prepared samples, with the maximum output voltage and current of 4.4 V and 0.66 μA, respectively, with an applied force of ~2N. Fine-tuning the BaTiO3 content and thickness of the PNGs is likely to increase the harvester’s performance even more. It is anticipated that the work would make it easier to fabricate high-performance piezoelectric films and would be a suitable choice for creating high-performance PNG.

Three-dimensional polypyrrole induced high-performance flexible piezoelectric nanogenerators for mechanical energy harvesting

Flexible piezoelectric nanogenerators (FPNGs) have received tremendous attention in terms of harvesting mechanical energy and driving portable devices. However, the weak interactions and interfacial defects between the fillers and matrix hinder from improving the flexibility and electromechanical properties of the composites, which limits the practical applications of nanogenerators. In this work, high-performance FPNGs based on all-organic composite thin films comprising of three-dimensional polypyrrole (3D PPy) and poly(vinylidene fluoride -hexafluoropropylene) [P(VDF-HFP)] are fabricated for the first time. The composite films exhibit excellent ferroelectric and piezoelectric properties, mainly resulting from the strong interfacial bonding between 3D PPy and the P(VDF-HFP) matrix. As a result, the FPNG prepared from the composites loaded with 5 wt% 3D PPy achieve considerable piezoelectric outputs (average power density of 5.52 μW/cm2 and peak power density of 10.84 μW/cm2). Meanwhile, the FPNGs can effectively obtain mechanical energy from human activities and still show a stable output after continuous operation over 3000 cycles. This work provides a novel idea to design and fabricate high-performance FPNGs through introducing conductive polymers into the matrix.

Unusual nanoscale piezoelectricity-driven high current generation from a self S-defect-neutralised few-layered MoS2 nanosheet-based flexible nanogenerator.

We report the fabrication of a high-performance flexible piezoelectric nanogenerator based on S-defect-neutralised few-layered molybdenum disulphide (MoS2) nanosheets. High-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy confirmed the number of stacked layers in the MoS2 sheets to be 3-5. The defect, electronic and chemical states of the as-grown MoS2 nanosheets were investigated by X-ray photoelectron spectroscopy (XPS). An as-fabricated MoS2 nanogenerator with a CNT electrode generates an excellent high output voltage of 22 V and a record-high output current density of 9.00 μA cm-2 under a small vertical compressive force of 1.5 kgf. The piezoelectric charge coefficient of the 2D MoS2 nanosheets was investigated using piezoelectric force microscopy (PFM), and a very high piezoelectric charge coefficient (d33) of 120 pm V-1 was obtained. The energy conversion efficiency of the device was about 30%. Moreover, the MoS2 nanosheets show a high dielectric constant of about 2649 at low frequency. The results suggest that the absence of S-defects can reduce the free charge carrier and screening effect, resulting in a high output voltage and current density. The performance of the nanogenerator is discussed in terms of its high d33, high dielectric constant, the crystalline mixed phase of MoS2 and the electronic state of the MoS2 nanosheets.

Enhanced piezoelectric performance of PVDF/BiCl3/ZnO nanofiber-based piezoelectric nanogenerator

A unique bismuth chloride (BiCl3)/zinc oxide (ZnO)/poly(vinylidene fluoride) (PVDF) nanofiber-based highly flexible piezoelectric nanogenerator (PENG) is prepared via electrospinning technique. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) are used to characterize the β-phase content and crystallinity of the PVDF based nanofibers, respectively. Then, we analyze four types nanofiber-based PENG (PVDF, PVDF/ZnO(2%), PVDF/BiCl3(2%), and PVDF/BiCl3/ZnO(2%)) and the influence factors of piezoelectric properties are addressed systematically. It is found that the longitudinal piezoelectric coefficient (d33) of PVDF/BiCl3/ZnO(2%) nanofiber-based PENG is up to 3.8 pC/N and an open-circuit voltage (VOC) of 12 V is also got. Finally, the practical applicability of the developed PENG is demonstrated by placing it on elbow and knee joint to monitor human body movement, which shows a maximum peak VOC of 3 V (for elbow) and 0.6 V (for knee) by bending and stretching between specific angles. The high-performance flexible PENG can be used as highly sensitive self-powered sensor, and it also can be used for wearable sensors for detecting some vital signals including breathing, heartbeating, which shows its possible applications in wearable electronics.

KNN/PDMS/C-based lead-free piezoelectric composite film for flexible nanogenerator

A novel approach to fabricate a high performance flexible piezoelectric nanogenerator (PNG) by employing K0.5Na0.5NbO3 (KNN)/PDMS/C composite thin film has been proposed. The formed 12 wt% C doping KNN/PDMS PNG demonstrates a higher relative permittivity (Ɛr, 173.56) and larger remanent polarization (Pr, 1.84 µC/cm2) than pure KNN/PDMS film, thus serving as the possible origins of their comparative piezoelectric activities, which could generate an maximum output voltage of 10.55 V (3.3 times as much as the PNG without C doping). Besides, the PNG is able to light up a commercial green light-emitting diode (LED) through an energy storage capacitor (47 µF), showing its great potential as power of wearable and mobile devices.

Self-Powered Piezoelectric Nanogenerator Based on Wurtzite ZnO Nanoparticles for Energy Harvesting Application

We report the synthesis procedure of hexagonal wurtzite structure of zinc oxide (ZnO) nanoparticles via hydrothermal route to use as a main component of piezoelectric nanogenerator. The ZnO nanoparticles are dispersed into polydimethylsiloxane (PDMS) to fabricate the high performance flexible piezoelectric nanogenerator (FPNG).The output voltage and power generated from the FPNG is around 20 V and 20 μW respectively. It is also capable to charge up the capacitors within very short span of time (for example, about 2V is reached at 96s). It is demonstrated that the output power generated from the FPNG can directly drive several commercial blue light emitting diodes (LEDs)that ensuring the applicability as a self-powered energy harvester.

Highly efficient flexible piezoelectric nanogenerator and femtosecond two-photon absorption properties of nonlinear lithium niobate nanowires

We present a high performance flexible piezoelectric nanogenerator (NG) device based on the hydrothermally grown lead-free piezoelectric lithium niobate (LiNbO3) nanowires (NWs) for scavenging mechanical energies. The non-linear optical coefficient and optical limiting properties of LiNbO3 were analyzed using femtosecond laser pulse assisted two photon absorption techniques for the first time. Further, a flexible hybrid type NG using a composite structure of the polydimethylsiloxane polymer and LiNbO3 NWs was fabricated, and their piezoelectric output signals were measured. A large output voltage of ∼4.0 V and a recordable large current density of about 1.5 μA cm−2 were obtained under the cyclic compressive force of 1 kgf. A subsequent UV-Vis analysis of the as-prepared sample provides a remarkable increase in the optical band gap (UV absorption cut-off, ∼251 nm) due to the nanoscale size effect. The high piezoelectric output voltage and current are discussed in terms of large band gap, significant nonlinear optical response, and electric dipole alignments under poling effects. Such high performance and unique optical properties of LiNbO3 show its great potential towards various next generation smart electronic applications and self-powered optoelectronic devices.

High‐Performance Piezoelectric Nanogenerators with Imprinted P(VDF‐TrFE)/BaTiO3 Nanocomposite Micropillars for Self‐Powered Flexible Sensors

Piezoelectric nanogenerators with large output, high sensitivity, and good flexibility have attracted extensive interest in wearable electronics and personal healthcare. In this paper, the authors propose a high-performance flexible piezoelectric nanogenerator based on piezoelectrically enhanced nanocomposite micropillar array of polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE))/barium titanate (BaTiO3 ) for energy harvesting and highly sensitive self-powered sensing. By a reliable and scalable nanoimprinting process, the piezoelectrically enhanced vertically aligned P(VDF-TrFE)/BaTiO3 nanocomposite micropillar arrays are fabricated. The piezoelectric device exhibits enhanced voltage of 13.2 V and a current density of 0.33 µA cm-2 , which an enhancement by a factor of 7.3 relatives to the pristine P(VDF-TrFE) bulk film. The mechanisms of high performance are mainly attributed to the enhanced piezoelectricity of the P(VDF-TrFE)/BaTiO3 nanocomposite materials and the improved mechanical flexibility of the micropillar array. Under mechanical impact, stable electricity is stably generated from the nanogenerator and used to drive various electronic devices to work continuously, implying its significance in the field of consumer electronic devices. Furthermore, it can be applied as self-powered flexible sensor work in a noncontact mode for detecting air pressure and wearable sensors for detecting some human vital signs including different modes of breath and heartbeat pulse, which shows its potential applications in flexible electronics and medical sciences.

High Performance Piezoelectric Nanogenerators Using Vanadium-Doped Ferroelectric ZnO Nanosheets and Polymer Composite

We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to signifi- cantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ∼32 V and ∼6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices.

High-performance flexible piezoelectric nanogenerators consisting of porous cellulose nanofibril (CNF)/poly(dimethylsiloxane) (PDMS) aerogel films

A novel, simple, cost-effective, and scalable technique was developed to fabricate high-performance flexible piezoelectric nanogenerators (NGs) using porous cellulose nanofibril (CNFs)/poly(dimethylsiloxane) (PDMS) aerogel film. The porous CNF/PDMS aerogel film was prepared by coating a layer of PDMS on the porous surface of a compressed CNF aerogel film produced via an environmentally friendly freeze-drying process. The porous CNF/PDMS aerogel film was then sandwiched between two thin PDMS films, followed by two aluminum foils, to form the flexible NGs. Under periodic external mechanical deformation by an oscillator, the resulting flexible porous CNF/PDMS aerogel film-based NGs exhibited very stable and high output piezoelectric signals; namely, an open-circuit voltage (Voc) of 60.2V, a short-circuit current (Isc) of 10.1μA, and a corresponding power density of 6.3mW/cm3. The electric power generated by these NGs was able to directly turn on 19 blue light-emitting diodes (LEDs) and charge a capacitor up to 3.7V. Furthermore, these NGs also demonstrated excellent stability and durability. Considering their excellent piezoelectric performance, ease of large-scale manufacturing, and environmental friendliness, this technology provides a promising solution for developing practical, flexible, and self-powered electronic devices.

High Performance Flexible Piezoelectric Nanogenerators based on BaTiO3 Nanofibers in Different Alignment Modes.

Piezoelectric nanogenerators, harvesting energy from mechanical stimuli in our living environments, hold great promise to power sustainable self-sufficient micro/nanosystems and mobile/portable electronics. BaTiO3 as a lead-free material with high piezoelectric coefficient and dielectric constant has been widely examined to realize nanogenerators, capacitors, sensors, etc. In this study, polydimethylsiloxane (PDMS)-based flexible composites including BaTiO3 nanofibers with different alignment modes were manufactured and their piezoelectric performance was examined. For the study, BaTiO3 nanofibers were prepared by an electrospinning technique utilizing a sol-gel precursor and following calcination process, and they were then aligned vertically or horizontally or randomly in PDMS matrix-based nanogenerators. The morphological structures of BaTiO3 nanofibers and their nanogenerators were analyzed by using SEM images. The crystal structures of the nanogenerators before and after poling were characterized by X-ray diffraction. The dielectric and piezoelectric properties of the nanogenerators were investigated as a function of the nanofiber alignment mode. The nanogenerator with BaTiO3 nanofibers aligned vertically in the PDMS matrix sheet achieved high piezoelectric performance of an output power of 0.1841 μW with maximum voltage of 2.67 V and current of 261.40 nA under a low mechanical stress of 0.002 MPa, in addition to a high dielectric constant of 40.23 at 100 Hz. The harvested energy could thus power a commercial LED directly or be stored into capacitors after rectification.

Direct Writing of Patterned, Lead-Free Nanowire Aligned Flexible Piezoelectric Device.

A high-performance flexible piezoelectric nanogenerator (PNG) is fabricated by a direct writing method, which acquires both patterned piezoelectric structure and aligned piezoelectric nanowires simultaneously. The voltage output of the as-prepared PNG is nearly 400% compared with that of the traditional spin-coated device due to the effective utilization of stress. This facile printing approach provides an efficient strategy for significant improvement of the piezoresponse.

A vanadium-doped ZnO nanosheets-polymer composite for flexible piezoelectric nanogenerators.

We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to significantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ∼32 V and ∼6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices.

Lithium-doped zinc oxide nanowires-polymer composite for high performance flexible piezoelectric nanogenerator.

We present a method to develop high performance flexible piezoelectric nanogenerators (NGs) by employing Li-doped ZnO nanowires (NWs). We synthesized Li-doped ZnO NWs and adopted them to replace intrinsic ZnO NWs with a relatively low piezoelectric coefficient. When we exploited the ferroelectric phase transition induced in Li-doped ZnO NWs, the performance of the NGs was significantly improved and the NG fabrication process was greatly simplified. In addition, our approach can be easily expanded for large-scale NG fabrication. Consequently, the NGs fabricated by our simple method exhibit the excelling output voltage and current, which are stable and reproducible during periodic bending/releasing measurement over extended cycles. In addition, output voltage and current up to ∼ 180 V and ∼ 50 μA, respectively, were obtained in the large-scale NG. The approach introduced here extends the performance limits of ZnO-based NGs and their potentials in practical applications.