Flexible Piezoelectric Energy Harvester Research Articles

A high-performance flexible piezoelectric energy harvester based on lead-free (Na0.5Bi0.5)TiO3–BaTiO3 piezoelectric nanofibers

A high-performance flexible piezoelectric energy harvester based on lead-free nanofibers.

High performance of macro-flexible piezoelectric energy harvester using a 0.3PIN-0.4Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 flake array

Harvesting energy from human motion to power wearable devices using flexible piezoelectric energy harvesters is becoming a hot research topic, since this approach could fix the charging problem related to batteries and would do no harm to the environment. Unlike nano-generators, which have a piezoelectric material thickness at the level of a few nm to a few μm, we present a high-performance macro-flexible piezoelectric energy harvester (MF-PEH) with a piezoelectric material thickness of 45 μm, based on a 0.3PIN-0.4PMN-0.3PT (PIMNT) long flake array with an optimized cut. The piezoelectric properties of (110)-oriented PIMNT were studied as a function of thickness and compared to those of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNT). The electrical properties of this device under different strain and load resistances are studied systematically. The results of our experiment show that under a strain of 0.225%, the open-circuit voltage and short-circuit current of MF-PEH reach levels as high as 23.2 V and 0.105 mA (at an excitation frequency of 1.1 Hz), respectively, with a maximum electric output power of 245 μW across a piezoelectric materials area of 400 mm2. We have also used the device to harvest mechanical energy from the motion of human knees and charge a battery successfully. Efficient conversion from mechanical energy to electric energy and large output power demonstrate that our MF-PEH is an important complement to flexible energy harvesters and a potential candidate as a self-powered source for wearable low-power electronics.

Worm structure piezoelectric energy harvester using ionotropic gelation of barium titanate-calcium alginate composite

A laterally aligned flexible composite linear worm-based piezoelectric energy harvester made up of piezoelectric barium titanate nanoparticles and a three dimensional gel network of calcium alginate biopolymer was aimed to harness the low frequency mechanical energy. It is highly desirable to fabricate innovative micro/nanostructures for high performance energy harvesting beyond the conventional thin films, and small scale fabrication of nanowires (or rods). The open circuit voltage of a single composite worm-based energy harvester (diameter ≈ 550 μm, length ≈ 2.5 cm) increases up to 5 times by increasing the frequency of mechanical load (11 N) from 3 to 20 Hz. Similarly, 1.5 times voltage increment was observed by increasing the length of the composite worm from 1.5 to 3.5 cm upon the bio-mechanical hand force. The energy harvester can function as an efficient portable/wearable self-powered device due to its good flexibility, and multiple lengths of composite linear worms can be utilized to drive low-power electronic devices. In this work, the composite worms were prepared by an ionotropic gelation approach, which is eco-friendly, non-toxic, having low processing temperature/time, and potential for cost-effective, large-scale fabrication, making it suitable for low frequency based self-powered devices.

Power Source for Wireless Sensors in Pipes

In this paper, we present investigations on wireless sensors for fluid control inside a pipe. Autarkic sensors are in the technical trend. They are typically connected with a transceiver unit for data transmission. Sensors usually need a lower amount of energy than data transceivers. Therefore, they are commonly supplied via wires or batteries with electricity. With common technologies, this request leads to high requirements on tightness in liquids since poor sealing could easily lead to failures. Replacement of batteries inside pipes is complicated and almost accompanied by a flow interruption. The application of energy harvesters as power supply is therefore a good alternative. In our studies we used flexible piezoelectric energy harvesters of PVDF (Poly-Vinylidene-Di-Fluoride). All harvesting units consist of piezoelectric PVDF-foils as active layers and Aluminum-foils as electrodes. The layers were stacked alternating on each other and wound to a spool. A LDPE-film wraps the spool and prevents the inflow of liquids. The device has following parameters: No. of windings: 4 in air, 4, 5, 7 in water Dimensions: 15 mm O 22mm Materials: PDVF: 25μm; Aluminimum: 6μm, LDPE: 25μm A ring shaped bluff body was placed inside the pipe to induce turbulence in the fluid stream. As the harvesters have been arranged downstream of the bluff body, they were forced to oscillate independent of the media. In each case, deformation of the active layers led to a polarization and a separation of electrical charges. Experiments were carried out in a wind channel as well as in a water pipe. In air, the spool oscillates with a frequency of about 30Hz, at a wind speed of about 7m/s. A -Voltage of about 4V (peak-peak) was measured. This delivers in case of power adjustment, power values of about 0.54μW. In water, the velocity of the fluid was limited to nearly one tenth. Oscillation starts only at a water speed above 0.6m/s. The average oscillation frequency is about 18Hz. At a velocity of 0.74m/s, a peak-peak-Voltage up to about 2.3V was found. In case of impedance adjustment, the power was about 0.33μW. This power is stored in a capacitor. Assuming a data transmission unit consumes about 0.2 mWs during one operational period of 1 second, the duty cycle time can be calculated to about 6.2 minutes for air harvesting and 10.1 minutes for harvesting in water.

Stretchable piezoelectric nanocomposite generator.

Piezoelectric energy conversion that generate electric energy from ambient mechanical and vibrational movements is promising energy harvesting technology because it can use more accessible energy resources than other renewable natural energy. In particular, flexible and stretchable piezoelectric energy harvesters which can harvest the tiny biomechanical motions inside human body into electricity properly facilitate not only the self-powered energy system for flexible and wearable electronics but also sensitive piezoelectric sensors for motion detectors and in vivo diagnosis kits. Since the piezoelectric ZnO nanowires (NWs)-based energy harvesters (nanogenerators) were proposed in 2006, many researchers have attempted the nanogenerator by using the various fabrication process such as nanowire growth, electrospinning, and transfer techniques with piezoelectric materials including polyvinylidene fluoride (PVDF) polymer and perovskite ceramics. In 2012, the composite-based nanogenerators were developed using simple, low-cost, and scalable methods to overcome the significant issues with previously-reported energy harvester, such as insufficient output performance and size limitation. This review paper provides a brief overview of flexible and stretchable piezoelectric nanocomposite generator for realizing the self-powered energy system with development history, power performance, and applications.

A Flexible Piezoelectric Pulsewave Energy Harvester for Application to High-Efficiency Multi-Functional Skin Patches

A piezoelectric pulsewave energy harvester composed of flexible three-layers generates electrical power from human arterial pulsewaves. We present the simple structure and novel fabrication process of the flexible three-layers, having a silver inter-electrode layer between a P(VDF-TrFE) piezoelectric layer and a polyimide support layer. The triple functions and the purposes of the silver inter-electrode layer are designed, acting as an electrode for piezoelectric poling, an electrode for piezoelectric energy harvesting, as well as an etch stop barrier for window patterning on the polyimide support layer. We also developed special processes for the window patterning on the polyimide support layer with the polyimide residue removal on the silver electrode, thereby increasing the piezoelectric energy generation efficiency and support flexibility, as well as achieving an electric contact to the silver electrode through the patterned window. The fabricated energy harvester generates $0.2\sim 1.9~\mu \text{W}$ from the human pulsewave in the range of $50\sim 220$ BPM, where the effect of window formation is demonstrated to increase energy efficiency and flexibility in the amount of 45% and 8%, respectively. The flexible energy harvester is capable to integrate additional physiological sensors for the applications to the multi-functional self-powered skin patches. [2015-0194]

Model refinements and experimental testing of highly flexible piezoelectric energy harvesters

This paper addresses limitations to existing analytical models for piezoelectric energy harvesters. The presented model is targeted at predicting behaviours of highly flexible piezoelectric devices (FPEDs) and includes high orders of substrate and piezoelectric material nonlinearity, geometric nonlinearity, and additionally the effects of both self-weight and pre-stress. Validation through experimental testing is provided.The influence of self-weight on vibratory dynamics becomes important in FPEDs due to both material composition and dimension. The developed model facilitates the simulation of FPED performance mounted at specified angles to the horizontal. In one study, for a FPED of 120mm in length, the resonant frequency changed by over 30 percent with mounting angle. Consideration of mounting orientation is advised as self-weight increases damping and significantly lowers FPED performance – over a 50 percent reduction in one presented case.

A flexible energy harvester based on a lead-free and piezoelectric BCTZ nanoparticle-polymer composite.

Lead-free piezoelectric 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 (BCTZ) nanoparticles (NPs) composed of earth-abundant elements were adopted for use in a flexible composite-based piezoelectric energy harvester (PEH) that can convert mechanical deformation into electrical energy. The solid-state synthesized BCTZ NPs and silver nanowires (Ag NWs) chosen to reduce the toxicity of the filler materials were blended with a polydimethylsiloxane (PDMS) matrix to produce a piezoelectric nanocomposite (p-NC). The naturally flexible polymer-based p-NC layers were sandwiched between two conductive polyethylene terephthalate plastic substrates to achieve a flexible energy harvester. The BCTZ NP-based PEH effectively generated an output voltage peak of ∼15 V and a current signal of ∼0.8 μA without time-dependent degradation. This output was adequate to operate a liquid crystal display (LCD) and to turn on six blue light emitting diodes (LEDs).

Fabrication of flexible nanogenerator with enhanced performance based on p-CuO/n-ZnO heterostructure

A p-CuO/n-ZnO heterostructure was synthesized on an indium tin oxide coated flexible substrate (polyethylene terephthalate) by a simple and low-cost hydrothermal method. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction were used to characterize the as-synthesized heterostructure. The results indicated that flower-like CuO nanostructure conformably formed on the ZnO nanorods. Furthermore, a nanogenerator based on the p-CuO/n-ZnO heterostructure was fabricated for harvesting energy from environment, and the output performance of the device was investigated. A larger output current of ~100 nA was obtained in comparison with ZnO based nanogenerator, which could be ascribed to the formation of p–n heterojunctions in the CuO/ZnO composites, reducing the screening effect of excessive electrons. This strategy may provide a highly promising platform for realizing a high-performance flexible piezoelectric energy harvester by new composite piezoelectric material.

Splitting of neutral mechanical plane of conformal, multilayer piezoelectric mechanical energy harvester

Flexible piezoelectric mechanical energy harvesters (MEHs) are of recent interest as an important emerging variant of traditional piezoelectric devices. The design of stacking multilayer MEHs with adhesive in between is an effective way to enhance the magnitude of power generation. Here, we present an analytic model to study the mechanical behavior of the multilayer MEHs based on lead zirconate titanate (PZT) subjected to Euler buckling. Being different from the hypothesis of the plane section for the entire stack, it is found that each polyimide (PI) layer holds plane section of its own, while soft adhesives serve as shear lags. Accordingly, the neutral mechanical plane is split into multiple ones. The deformation is almost the same for each PI layer, as well as PZT arrays, which is very beneficial to avoid the premature failure of devices. The extreme cases and the transition of these cases are all captured quantitatively with a unified analytic model which is verified by the finite element method. A dimensionless parameter is obtained to characterize the degree of the splitting of neutral mechanical plane, which is significant for the design of the multilayer PZT MEHs.

Flexible Two-ply Piezoelectric Yarn Energy Harvester

We developed a flexible two-ply piezoelectric yarn-type generator using an electrospun polyvinylidenefluorideco- trifluoroethylene (PVDF–TrFE) mat and a commercially available silver-coated nylon fiber. By rolling the silvercoated nylon fiber into the electrospun PVDF–TrFE mat as the inner electrode, the two-dimensional piezoelectric PVDF– TrFE mat was easily transformed into a one-dimensional fiber. Then silver-coated nylon fiber rolled in PVDF–TrFE was plied with another similar fiber to make a flexible two-ply piezoelectric yarn. The overall fabrication processes of the flexible two-ply piezoelectric yarn are simple and have a high application potential. The flexible two-ply piezoelectric yarn can generate up to 0.7 V in compression and 0.55 V in tension. The yarn retained the piezoelectric performance in various shapes, such as a sewn structure. In addition, the piezoelectric performance was sensitive to velocity and pressure. The flexible two-ply piezoelectric yarn has potential applications as a human motion sensor, as a building block of energy- harvesting textiles, and in self-powered biomedical applications. Keywords: Energy harvester, Flexible, Piezoelectric, Two-ply, Wearable, Yarn.

Flexible ceramic-elastomer composite piezoelectric energy harvester fabricated by additive manufacturing

As a renewable energy harvesting method, interest in piezoelectric energy harvesting has increased significantly. Despite the piezoelectric energy-harvesting technology expanding its area to the flexible (elastic, amendable) devices, striking use or application of the technology is hardly found in the market. Here, we report a novel flexible piezoelectric energy harvester fabricated by using an additive manufacturing process, which enables both effective and customized manufacturing technique. By taking advantages of additive manufacturing, further application of the piezoelectric energy-harvesting technology is highly expected. Particles of BaTiO3, a ceramic with a large piezoelectric constant, were mixed with polyether block amide elastomer to form a flexible piezoelectric composite. The energy harvester was fabricated using an additive manufacturing process, by printing the piezoelectric composite on a laser-patterned flexible Indium-tin-oxide–coated polyethylene terephthalate substrate. Performance of fabricated energy harvester was evaluated by applying a mechanical stress to the energy harvester; voltage and current output were 2 V and 40 nA, respectively. An analytical model of the piezoelectric energy harvester was developed and discussed to explain the form of the voltage waveforms in response to the applied stress.

Powerful curved piezoelectric generator for wearable applications

With the widespread use of wearable electronics, the flexible piezoelectric energy harvesting devices have been extensively studied to efficiently convert the physical motion of the human body into electrical energy. The major obstacles for realizing a flexible piezoelectric generator include the insufficient output power generation and the poor efficiency at the low-frequency regime. Here, we demonstrate a curved piezoelectric generator favorable for wearable applications, generating a high output power. The curved structure plays a key role to improve the power generation, by effectively distributing the applied force across the piezoelectric layer, as well as to allow operation at the low frequency vibration range. Accordingly, this generator produces ~120V of peak output voltage and ~700µA of peak output current during a cycle. Furthermore, our generator can operate at low frequencies below 50Hz, generating ~55V of output voltage and 250µA of output current at 35Hz, and it even works at frequencies as low as 1Hz. With this generator, we successfully lit up 476 commercial LED bulbs. In addition, we experimentally demonstrate the possibility that the generator can be used in shoes, watches, and clothes as a power source. Our results will provide a framework to enhance the output power of conventional piezoelectric generators, and open a new avenue for realization of self-powered systems, such as wearable electronic devices.

Self-powered deep brain stimulation via a flexible PIMNT energy harvester

A self-powered deep brain stimulation has been demonstrated by a flexible piezoelectric PIMNT energy harvester to induce behavioural changes in a mouse.

A Flexible Piezoelectric Energy Harvesting System for Broadband and Low-frequency Vibrations

A piezoelectric energy harvesting system, where elastomer pillars stand on a piezoelectric polymer layer is designed, fabricated and tested for low and broadband frequency vibrations. In this configuration, elastomer pillars behave like a set of oscillators on the vibrating structure, which provide absorption of vibration energy and act as an energy sink. Then, the stored elastic energy is converted to electrical energy in the clamped boundary via stress concentration on the piezoelectric layer. A single pillar system with 10mm diameter and aspect ratio of 3 with an active area of 39 mm2 and thickness of 28μm generate a voltage of 4.5V and an output power of 58.4μW for an input acceleration of 3g at 62Hz with optimized load resistance condition.

Flexible piezoelectric thin-film energy harvesters and nanosensors for biomedical applications.

The use of inorganic-based flexible piezoelectric thin films for biomedical applications has been actively reported due to their advantages of highly piezoelectric, pliable, slim, lightweight, and biocompatible properties. The piezoelectric thin films on plastic substrates can convert ambient mechanical energy into electric signals, even responding to tiny movements on corrugated surfaces of internal organs and nanoscale biomechanical vibrations caused by acoustic waves. These inherent properties of flexible piezoelectric thin films enable to develop not only self-powered energy harvesters for eliminating batteries of bio-implantable medical devices but also sensitive nanosensors for in vivo diagnosis/therapy systems. This paper provides recent progresses of flexible piezoelectric thin-film harvesters and nanosensors for use in biomedical fields. First, developments of flexible piezoelectric energy-harvesting devices by using high-quality perovskite thin film and innovative flexible fabrication processes are addressed. Second, their biomedical applications are investigated, including self-powered cardiac pacemaker, acoustic nanosensor for biomimetic artificial hair cells, in vivo energy harvester driven by organ movements, and mechanical sensor for detecting nanoscale cellular deflections. At the end, future perspective of a self-powered flexible biomedical system is also briefly discussed with relation to the latest advancements of flexible electronics.

A Skin-attachable Flexible Piezoelectric Pulse Wave Energy Harvester

We present a flexible piezoelectric generator, capable to harvest energy from human arterial pulse wave on the human wrist. Special features and advantages of the flexible piezoelectric generator include the multi-layer device design with contact windows and the simple fabrication process for the higher flexibility with the better energy harvesting efficiency. We have demonstrated the design effectiveness and the process simplicity of our skin- attachable flexible piezoelectric pulse wave energy harvester, composed of the sensitive P(VDF-TrFE) piezoelectric layer on the flexible polyimide support layer with windows. We experimentally characterize and demonstrate the energy harvesting capability of 0.2~1.0μW in the Human heart rate range on the skin contact area of 3.71cm2. Additional physiological and/or vital signal monitoring devices can be fabricated and integrated on the skin attachable flexible generator, covered by an insulation layer; thus demonstrating the potentials and advantages of the present device for such applications to the flexible multi-functional selfpowered artificial skins, capable to detect physiological and/or vital signals on Human skin using the energy harvested from arterial pulse waves.

Flexible piezoelectric energy harvesting from jaw movements

Piezoelectric fiber composites (PFC) represent an interesting subset of smart materials that can function as sensor, actuator and energy converter. Despite their excellent potential for energy harvesting, very few PFC mechanisms have been developed to capture the human body power and convert it into an electric current to power wearable electronic devices. This paper provides a proof of concept for a head-mounted device with a PFC chin strap capable of harvesting energy from jaw movements. An electromechanical model based on the bond graph method is developed to predict the power output of the energy harvesting system. The optimum resistance value of the load and the best stretch ratio in the strap are also determined. A prototype was developed and tested and its performances were compared to the analytical model predictions. The proposed piezoelectric strap mechanism can be added to all types of head-mounted devices to power small-scale electronic devices such as hearing aids, electronic hearing protectors and communication earpieces.

Flexible piezoelectric vibration energy harvester using a trunk-shaped beam structure inspired by an electric fish fin

This paper presents a bio-inspired structure that can enhance the efficiency of piezoelectric power generation in vibration-type energy harvester. Inspired by an electric fish, Gnathonemus petersii, a trunk structure for high-performance vibration energy harvester is explored. The proposed vibration energy harvester consists of a flexible PVDF film and thin glass fiber plate shaped with auxiliary delta wings to mimic the trunk structure of the electric fish. An experimental study of the prototype energy harvester shows that the proposed piezoelectric vibration energy harvester featuring the new bio-inspired structure produces 45% more power output than the conventional vibration energy harvester due to its electret-like material behavior.

Nanogenerators: Self‐Powered Cardiac Pacemaker Enabled by Flexible Single Crystalline PMN‐PT Piezoelectric Energy Harvester (Adv. Mater. 28/2014)

A self-powered artificial pacemaker is demonstrated using a high-performance flexible piezoelectric PMN-PT thinfilm energy harvester. As reported by K. J. Lee and co-workers on page 4880, a PMN-PT harvesting device can convert slight mechanical movements to high electric power and provides functional electrical stimulation of a living heart.