Flexible Piezoelectric Generator Research Articles

Flexible BTO piezoelectric generator fabricated by hydrothermal method with the assistance of lignocellulose and carbon nanomaterials

It is of great significance to develop piezoelectric composites with mechanical flexibility and high electromechanical coupling characteristics for the collection and conversion of mechanical energy. In this work, a barium titanate (BTO) based piezoelectric composite was prepared by hydrothermal synthesis and high-temperature carbonization with the assistance of cellulose nanofibers (CNF), graphene oxide (GO) and carboxylated carbon nanotubes (C-CNT). C-CNT, GO and CNF can provide growth sites for BTO, but compared with C-CNT, CNF and GO have stronger interaction with BTO, which can improve the compatibility between BTO and CNF/polyvinylidene fluoride (PVDF) matrix. The tensile strength of the composite membrane prepared by GO-CNF-BTO treated at 1100 °C can reach 23.36 ± 8.30 MPa. After further hot pressing and polarization treatment, its longitudinal piezoelectric coefficient (d33) reaches 9.8 ± 2.6 pC·N−1. Correspondingly, the open-circuit voltage (VOC) and short-circuit current (ISC) increases to 11.64 V and 824 nA, respectively. In addition, the assembled piezoelectric generator (PEG) can charge for small commercial capacitors, as well as light small bulbs and electronic screens. It also has good piezoelectric output stability and sensing performance, which can effectively convert the mechanical energy from human motion into electrical energy. This work provides a reference for the performance improvement of flexible piezoelectric devices.

Electromechanical Performance and Figure of Merit Optimization for Flexible Lead-Free PDMS-BaTiO 3 Piezocomposites.

In the modern era of the Internet of Things, the potential role of flexible piezoelectric generators (PEG) reflects the rapid increase in self-powered devices and wearable technologies. In this study, a casting process to elaborate the polydimethylsiloxane (PDMS)/barium titanate (BaTiO 3) composite has been presented. The addition of 15 wt % BaTiO 3 microparticles into the PDMS polymer greatly enhances the piezoelectric coefficient (d 31 = 24 pC N-1), leading to an increased output voltage of approximately 4 V under finger tapping force. The proposed flexible microgenerator yielded an excellent piezoelectric figure of merit (FoM 31 = 13.1 × 10-12 m2 N-1), significantly enhancing successfully the energy-harvesting performance (power density of 35 nW/cm2). Furthermore, the fabricated lead-free PEG exhibited an excellent flexibility figure of merit (fFoM) due to the low young modulus values (Maximum E = 3.4 MPa). These results indicate efficient energy conversion and demonstrate a favorable balance between the flexibility and piezoelectric properties of the composite, highlighting its potential for a wide range of applications in self-powered wearable sensors able to collect different human motions in applications such as gesture tracking and finger motion detection.

PZT thick film element balancing flexibility with piezoelectricity fabricated by electrohydrodynamics jet printing used for micro power generator

In this paper, a novel flexible piezoelectric thick-film generator is proposed to address the challenges caused by flexible deformation and high piezoelectricity. This improves the output charge of the generator, which breaks the limitation imposed by the rigid and brittle nature of traditional piezoelectric bulks on elastic strain and piezoelectric performance. Additionally, the low piezoelectric coefficient of piezoelectric polymer-based piezoelectric generators is also resolved. Given the high thickness precision of electrohydrodynamic jet printing technology, the facile production of 10-μm thick film components is achieved through a process of printing and layer-by-layer accumulation on a flexible substrate, which ensures the flexible deformation and piezoelectric characteristics of the functional film. To ensure that AC is converted into stable DC output, a bipolar charge collection circuit is developed. The printed thick film produces an excellent performance in surface uniformity and smoothness. Notably, the piezoelectric constant d33 is measured to be approximately 80 pC/N, which is five times higher than the d33 value of flexible PVDF films. Additionally, the strength of adhesion between the printed thick film and the flexible substrate is remarkably high, reaching up to 20 N, which is an order of magnitude higher than the magnetron sputtering method. In a single cycle, the forward charge output reaches an impressively high level of 260 nC, which is approximately thirteen times the charge transfer capability of PVDF flexible generator. Furthermore, a bipolar charge collection circuit is applied to convert AC into DC effectively. This increases the output voltage from 2 V to 4 V. The illumination of commercial electronic screens and 39 LED lights demonstrates the applicability of micron-scale jet-printed thick films in micro-energy harvesting.

Metal-doped functional zinc oxide nanosheets as flexible piezoelectric generator for self-powered mechanical sensing

The development of self-powered active mechanical sensors, which enable tactile sensing capabilities for soft robotics, has been substantially accelerated by the invention and rapid advancement of piezoelectric nanogenerators that harness mechanical energy from the environment as electricity. However, fabrication methods and sensory output expansion of nanogenerators are still challenging to meet the stability and durability requirements during prolonged use. In this work, metal-doped zinc oxide nanomaterial-polymer composites are prepared, characterized, and fully embedded in the flexible substrates to fabricate piezoelectric sensors with enhanced output performance and sensing capabilities. The flexible device can generate an open-circuit voltage up to 13.6 V when the applied force is 8 N at 3 Hz. In addition, these lead-free composite devices exhibit remarkable elbow motion detection sensitivity, providing a tremendous potential for precise human body motion sensing. Further, based on the sensors, a biomimetic soft robotic fin with mechanosensation has been developed, which can measure both the amplitude and frequency of the flapping of the fin ray. These findings not only shed new light on the development of functionl piezoelectric nanogenerators, but also lay the framework for advanced ambient sensing capacities of underwater organisms or robots.

Development of KNNLTS–PVDF-based flexible piezoelectric generator for energy-harvesting application

Development of KNNLTS–PVDF-based flexible piezoelectric generator for energy-harvesting application

Output characteristic of thin-film flexible piezoelectric generator with pure bending deformation via pneumatic energy excitation

Various flexible piezoelectric generators based on thin films are increasingly popular due to their high flexibility and long service life. Insufficient output power is the crucial problem restricting the application of flexible piezoelectric generators, whose piezoelectric capability usually depends on large strain deformation. Pure bending deformation is the primary method to give full play to its piezoelectric performance. This study demonstrates the output characteristics of a thin-film flexible piezoelectric generator under pure bending deformation via pneumatic energy excitation. The induced stress and output voltage of a flexible piezoelectric generator under different bending deformations are simulated by the finite element method (FEM) and verified by experiments. The output characteristics of a flexible piezoelectric generator with different parameters are studied, including the substrate position, the pre-bending, the velocity, the bending displacement, the aspect ratio of polyvinylidene fluoride (PVDF) film, and the thickness of the substrate. When the substrate thickness is 0.25 mm, and the PVDF aspect ratio is close to 0.6, the output performance of the flexible piezoelectric generator is better. The concept of direct current (DC) average power is proposed for the first time, and its power characteristics and load characteristics at different frequencies are studied. The peak and average power of the 8 stacked piezoelectric units in parallel can reach 4.45 mW and 0.686 mW at 6 Hz. This study can provide essential guidance for understanding the output characteristics of flexible piezoelectric generators with pure bending deformation, and promote their application in the field of pneumatic system energy capture.

Energy storage and catalytic behaviour of cmWave assisted BZT and flexible electrospun BZT fibers for energy harvesting applications

High-performance lead-free Barium Zirconium Titanate (BZT) based ceramics have emerged as a potential candidate for applications in energy storage, catalysis for electro chemical energy conversion and energy harvesting devices as presented in this work. In the present study hybrid microwave sintered BZT are studied for dielectric, ferroelectric and phase transition properties. BZT ceramic exhibits tetragonal structure as confirmed by the Retvield refinement studies. XPS studies confirms the elemental composition of BZT and presence of Zr. Polarization versus electric field hysteresis loops confirms the ferroelectric behaviour of BZT ceramic. Encouragingly, the BZT showed a moderate energy storage efficiency of 30.7 % and relatively good electro chemical energy conversion (HER). Excellent catalytic activity observed for BZT electrode in acid medium with low Tafel slope 77 mV dec-1. Furthermore, electrospun nanofibers made of PVDF-HFP and BZT are used to make flexible piezoelectric nano generators (PENGs). FTIR studies show that the 16 wt% BZT composite ink exhibits a higher electroactive beta phase. The optimized open-circuit voltage and short circuit current of the flexible PENG exhibits 7Vpp and 750 nA under an applied force of 3N. Thus, flexible and self-powered BZT PENGs are alternative source of energy due to its reliability, affordability and environmental-friendly nature.

Vanadium disulfide-incorporated polymer nanocomposites for flexible piezoelectric energy generators and road safety sensors

Piezoelectric materials have attracted considerable attention in the field of flexible electronics owing to their ability to convert mechanical strain into electrical energy.

A flexible piezoelectric generator based on KNN/PVDF composite films: Role of KNN concentration on the piezoelectric performance of generator

A flexible piezoelectric generator based on KNN/PVDF composite films: Role of KNN concentration on the piezoelectric performance of generator

Fully flexible thermoelectric and piezoelectric hybrid generator based on a self-assembled multifunctional single composite film

Thermoelectric and piezoelectric hybrid generators (TPHGs) are attractive candidates for powering wearable body sensor networks continuously and permanently owing to their excellent access to human-generated energy. Herein, we propose a fully flexible single film-based TPHG comprising n-type Bi2Te2.7Se0.3 particles and poly(vinylidene fluoride-co-trifluoroethylene). The hybrid generator was assembled through simple drop-casting and gravitational settling effect, for the first time. The film layer sedimented with the conductive thermoelectric particles simultaneously served as an electrode and a bottom substrate for piezoelectric energy harvesting. The fabricated device generated outputs of 1 μA and 4 V at a temperature difference of 3 K and a bending displacement of 5 mm; these values indicate that the thermoelectric and piezoelectric effects were combined well without compromising the energy harvesting performance of each part. Furthermore, the fabricated device exhibited robust mechanical durability for ∼5000 bending cycles; this result was better than those of previously reported flexible TPHGs (f-TPHGs). The proposed design concept for f-TPHGs can aid in the development of high-performance multisource energy harvesting devices for wearable sensors.

Improving the performance of flexible composites based on 3-3 interconnected skeletons for piezoelectric energy harvesting

With the rapid development of microelectronics and portable devices, flexible piezoelectric electricity generators (FPEGs) as self-powered devices have attracted extensive attention. Piezoelectric ceramic-polymer composites with good flexibility is the core component of FPEGs. Having high d33 and g33 values is also essential for power generation. Herein, the porous ceramic skeleton is prepared using PZT based as the ceramic powder and polyurethane sponge as the template, followed by compounding the porous ceramic skeleton with polydimethylsiloxane (PDMS) by vacuum impregnation to prepare a 3-3 interconnected composite. When the ratio of ceramic phase in the ceramic slurry is 75 wt%, the volume fraction of the ceramic phase in the composite can achieve 37 vol%. Before compounding PDMS, porous ceramics are polarised, which is called pre-polarisation. The d33 value of the pre-polarised composites can reach 158 pC/N as compared to not polarising the porous ceramic and then polarising it after composite; the improvement is 48%. In addition, the g33 value of the pre-polarized composites is up to 144 mV m/N. Moreover, the 3.0 × 1.2 × 0.2 cm3 FPEG can generate a maximum output voltage of 15 V and a maximum short circuit current of 167 nA at 9% compression strain. The maximum instantaneous power density is 990 nW/cm2, thereby providing a new idea for piezoelectric power generation.

Flexible horizontal piezoelectric energy generator for sea wave applications

Energy harvesting from the environment becomes a valuable technology, especially for sea wave applications, in which it usually ends up wasted despite its potential to be harvested. Due to its wide availability and high energy density, piezoelectric energy harvesting (PEH) is becoming popular for flexible energy harvesting. This paper presents a flexible horizontal piezoelectric (FHP) energy harvester to harvest energy from the surface of sea wave. The harvester is made of bimorph piezoelectric devices; they are utilised to amplify and convert the collected mechanical vibrations into electrical power. A finite element model is established from ANSYS simulations to solve the iteration method by generating resonance frequency (fr). Then, Taguchi method, SN ratio and the ANOVA approach were used by considering the input variable of fr to estimate the optimum performance through control factors; number of blade, length and thickness. From the performance test result, it is proven that the higher numbers of blade including length, and minimum numbers of thickness significantly improve the significant level, α = 0.05% of ANOVA. Three prototypes are developed with approximate body dimensions through the resonance frequency perform and generate a 160.3 Hz on blade dimensions of 10 × 300 × 0.2 mm, with a piezoelectric (PZT) on its surface. This particular study shows that the potential of output power is generated from sea wave surface through a significant relationship between length, thickness, and blade design. This research develops a novelty for energy harvesting from flexible piezoelectric generator on sea wave application that could be easily install on offshore platform.

Flexible piezoelectric generator based on PLLA/ZnO oriented fibers for wearable self-powered sensing

Herein, PLLA/ZnO oriented fibers were prepared via orientation electrospinning towards a piezoelectric generator, omitting polarization and stretching postprocesses. The composite fibers achieved macroscopic orientation and molecular alignment, as well as higher crystallinity and more polar phase for PLLA. Collectively, the resulting generator exhibited dramatic and stable piezoelectric signals over 1000 s, boosting the open-circuit voltage to 7.9 V, nearly 4.6 times larger than that of the random neat device. With the same changing tendency, the simulated results confirmed oriented fibers and ZnO induced stress concentration, imparting better piezoelectricity. Furthermore, the generated electricity from the generator with a short-circuit current of 286nA and an output power density of 1.25 mW cm−3 charged a 10 μF capacitor up to 2 V at 210 s then illuminated a LED. Encouragingly, high flexibility and sensitivity allowed this device to function as a wearable self-powered sensor for differentiating human movement and monitoring human health.

Enhanced poling efficiency via a maximized organic-inorganic interfacial effect for water droplet-driven energy harvesting

Piezoelectric fluoropolymers that can convert mechanical energy to electricity have attracted intensive attention in sustainable power sources for microelectronics. However, in order to achieve high energy conversion efficiency in fluoropolymers, an electrical poling under a high electric field is an unavoidable high energy-consumption process. Herein, we demonstrated the enhanced poling efficiency in nanocomposite made of poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) and porous BaTiO3 nanofibers (BT NFs). The high specific surface area of porous BT NFs maximized the P(VDF-TrFE)-BT interfacial region, which produces rapid reorientation of dipole moments under electric field; this behavior effectively improved the poling efficiency of the piezoelectric nanocomposite. Subsequently, we fabricated an flexible piezoelectric nanocomposite generator (PNCG), which generated an open-circuit voltage of ~13.1 V and a short-circuit current of ~2.0 μA with a relatively low electric field of 200 kV cm−1. Furthermore, the PNCG is realized in a real-world environment and generates sufficient power to charge a commercial capacitor by harvesting mechanical energy from falling water droplets. This work provides a low-energy consumption pathway for developing high-performance piezoelectric devices for practical applications.

Fabrication of β-Phase-Enriched PVDF Sheets for Self-Powered Piezoelectric Sensing.

The fabrication of self-powered pressure sensors based on piezoelectric materials requires flexible piezoelectric generators produced with a continuous, large-scale, and environmentally friendly approach. In this study, continuous poly(vinylidene fluoride) (PVDF) sheets with a higher β-phase content were facilely fabricated by the melt-extrusion-calendering technique and a PVDF-based piezoelectric generator (PEG) was further assembled. Such a PEG exhibits a remarkable piezoelectric output performance. Moreover, it possesses prominent stability even after working for a long time, exhibiting potential applications for real-time monitoring of various human movements (i.e., hopping, running, and walking) and gait. This work not only provides the possibility of continuous and environmentally friendly fabrication of PVDF sheets with remarkable piezoelectric properties but also paves a new promising pathway for powering portable microelectronic applications without any external power supply.

Self-powered smart patch promotes skin nerve regeneration and sensation restoration by delivering biological-electrical signals in program

Skin wound is always accompanied with nerve destruction. Due to the limited clinical treatment option, loss of skin sensation with unsatisfactory nerve regeneration is remained to be a challenge for wound therapy. Endogenous mesenchymal stem cells (MSCs) based in situ regeneration, of which, MSCs recruited by chemokines and directed for neuronal differentiation by biological and electrical signals have been thought a novel strategy with potential to accelerate the nerve regeneration and sensory functions recovery. However, most current therapeutic systems usually deliver the chemokines, biological and electrical signals separately and statically, resulting in limited nerve regeneration and sensory functions recovery. Moreover, most of the devices for providing electrical signals need external energy input and complicated practice, leading to poor compliance in patients. To address these issues, we propose a self-powered smart patch (PRG-G-C) to provide chemokine and biological-electrical cues in program. PRG-G-C was composed of a flexible piezoelectric generator to supply electrical stimulation and a conductive gel, which served as the reservoir of chemokine and neural directing exosomes as well as the electrode to transfer electric cue. PRG-G-C was shown to efficiently accelerate rapid nerve regeneration and sensation restoration at the wound site within 23 days. This study demonstrates a proof-to-concept in organizing chemokine, neural directing biological-electrical heterogeneous cues within a self-powered smart patch for accelarating nerve regeneration and sensation restoration, possessing great potential in neural repair applications.

Enhanced electromechanical conversion via in situ grown CsPbBr3 nanoparticles/poly(vinylidene fluoride) fibers for physiological signal monitoring

Mechanical energy conversion based on piezoelectric principle has received much attention due to its promising applications in sustainable power supply systems and sensor technology. Ferroelectric poly(vinylidene fluoride) (PVDF) combines the advantages of both good electromechanical coupling and easy processability, yet the low piezoelectric coefficient limits its output performances thus cannot meet the increasing requirements for power generation and sensing. Here, inorganic metal halide perovskite CsPbBr3 (CPB) nanoparticles have been incorporated into the PVDF fibers via electrospinning technique, where an in situ crystallization and growth process of CPB nanoparticles have been established. Meanwhile, both the CPB nanoparticles and PVDF fibers are poled by the electric field during electrospinning process, which promotes the formation of polar phase of PVDF and the distortion of CPB lattice, resulting in greatly enhanced piezoelectric performances of CPB/PVDF composites. The output performances under external force of the flexible generator developed from electrospun CPB/PVDF films are significantly enhanced compared with neat PVDF film, with the maximum Voc value 8.4 times higher; while the measurements on the microscopic piezoelectric responses unambiguously reveal that the increased polar phase mainly contributes to the enhanced electromechanical coupling. The functions of CPB/PVDF film as physiological signals monitoring sensor have been performed, demonstrating its potential applications as flexible piezoelectric generator and wearable health monitoring electronics.

Energy Harvesting by Flexible Piezoelectric Generator for Tag Attached on the Oscillating Fish Tail

Energy Harvesting by Flexible Piezoelectric Generator for Tag Attached on the Oscillating Fish Tail

Design on orientation of one-dimensional ZnO/P(VDF-HFP) nanocomposites for significant enhanced electromechanical conversion

Flexible piezoelectric generators (PEGs) are receiving considerable attention due to the increasing demands on lightweight and sustainable power supply for wearable electronics. Combing piezoelectric nanofillers with polymers have been extensively investigated as a promising strategy. Here, piezotronic ZnO nanorods are introduced into poly (vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] considering that piezoelectric functions of both components can be united for high performance PEGs. ZnO/P(VDF-HFP) nanocomposites were designed with fillers distribution controlled via different processing, and the relationship between the filler orientation and the crystallization behaviors, dielectric and electromechanical conversion performances with respect to filler content were studied. The microcapacitor model and percolation theory were employed to understand the dielectric anisotropy in oriented nanocomposites, and furthermore, finite element analyses were utilized to reveal the distribution of local electric field. Finally, a maximum output voltage 11.8 V has been achieved in oriented ZnO/P(VDF-HFP) film, which is 2.3 times and 7.9 times the value of random nanocomposites (5.1 V) and pure P(VDF-HFP) film (1.5 V), respectively. With the piezoelectric responses obtained from piezoelectric force microscopy, significant enhancement in electromechanical conversion performance has been thoroughly discussed. The results thus demonstrate a promising strategy towards high-performance flexible piezoelectric generator.

A Harvesting Circuit for Flexible Thin-Film Piezoelectric Generator Achieving 562% Energy Extraction Improvement With Load Screening

In this article, a novel energy harvesting (EH) interface for a flexible thin-film piezoelectric generator (FPEG) is proposed for EH from irregular human motion. The traditional thick piezoelectric generator (PEG) based kinetic EH circuits are designed for continuous and sinusoidal inputs from the cantilever-based structures and are not suitable for EH from irregular human motion. The proposed EH interface circuit significantly enhances energy extraction with a load-screening scheme, which minimizes the load capacitance to maximize the PEG output voltage up to 102 V while using the standard voltage 0.18- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m process. An energy-aware wake-up controller is designed to (monitor and) detect the FPEG deformation to assure that the harvesting interface is only activated when enough energy is available for EH. When the FPEG voltage peaks, the energy is transferred to the battery through an inductor with a single-cycle buck-converter-like operation, allowing the input voltage and frequency-independent EH operation. The measurement results show that the proposed EH interface successfully harvests energy from irregular pulsed inputs with 562% improvement compared with a full-bridge rectifier.