Flexible Piezoelectric Devices Research Articles

Zinc tungstate integrated onto zinc oxide h-MDs-based flexible piezoelectric power device: A new energy technology for real-time indoor laboratory safety warning system

With the rapid development of research world, the number of researchers and research laboratories is increasing rapidly. Simultaneously, accidents in laboratories are on the rise, drawing significant attention from everyone. To address this issue, the current study demonstrates a real-time safety early warning alarm system aimed at preventing accidents and enhancing safety management in laboratories. We developed a zinc tungstate nanoparticles (NPs) integrated on zinc oxide hexagonal microdiscks (h-MDs) (ZnO–ZnWO4@PDMS) composite based on a novel flexible piezoelectric nanogenerator (FPENG). The observed piezoelectric response was 1.32 V, which is ∼4 times better than that of pure ZnWO4, owing to the synergistic effect of ZnO–ZnWO4@PDMS. When subjected to finger-tapping motion, the FPENG can charge a 1 μF capacitor, and it reached 81 mV within 56 s. Subsequently, the light-emitting diodes (LEDs) are powered with amplification. The FPENG system was demonstrated and validated through real-time application in the laboratory setting, marked as a “caution/restricted” line. The application of the system demonstrated its capability to simultaneously illuminate LEDs and sound alarms when people touch or cross the caution line. Furthermore, the proposed FPENG exhibited ∼660 mV even ∼90 % humidity, with no noticeable electrical changes under different solvents, confirming that the proposed FPENG is not affected by varying humidity and various indoor conditions. These outstanding results and real-time demonstrations unequivocally establish the feasibility of this system in contexts such as bank lockers, metro systems, hilly areas, and more.

Flexible piezoelectric sensor based on polyvinylidene fluoride/polyacrylonitrile/carboxy-terminated multi-walled carbon nanotube composite films for human motion monitoring

Flexible piezoelectric devices have attracted much attention in the fields of intelligent devices and biomedicine because of their high sensitivity, stability, and flexibility. In this paper, a multifunctional flexible pressure sensor was prepared by adding polyacrylonitrile (PAN) and carboxylic-terminated multi-walled carbon nanotubes (c-MWCNTs) with polyvinylidene difluoride (PVDF) as the substrate. The β-phase content of PVDF/PAN blended fibers compounded with c-MWCNT was up to 95%. At the same time, when PAN was added, the mechanical properties of the composite fibers were constantly improved. The results show that the polymer blending method can improve the comprehensive properties of PVDF composite. The flexible sensor prepared from the PVDF/PAN/c-MWCNT composite film has an output voltage of 2.1 V and a current of 7 μA. The addition of c-MWCNT can largely improve the sensitivity of the sensor (4.19 V N−1). The sensor is attached to the finger and shows good output performance under different degrees of bending of the finger. The maximum output voltage of the sensor is 0.4 V, 0.56 V and 1.15 V when the finger bending angle is 30°, 60°, and 90°, respectively. Moreover, the developed piezoelectric sensor can monitor large-scale movements of various parts of the human body. Therefore, this composite material shows potential in areas such as motion monitoring and energy storage devices.

Effective-performance of inorganic and organic (barium zirconium titanate/polyvinylidene fluoride) piezoelectric composite for energy harvesting and self-powered smart IoT-based electronics

In the context of the rapidly advancing fields of energy harvesting and the Internet of Things (IoT), flexible piezoelectric materials have received significant attention for powering and providing sensing signals to electronic devices. In this study, piezoelectric barium zirconium titanate (BZT) material was synthesized via a solid-state reaction method at high temperatures. The synthesized BZT was incorporated as a filler in the PVDF polymer matrix to design a flexible piezoelectric device using a solvent-casting method. Structural analyses verified the formation of the tetragonal structure (P4mm) of BZT and the successful composite with PVDF. Piezoelectric properties of PVDF and BZT/PVDF were tested under mechanical force, revealing that the BZT/PVDF composite exhibited higher voltage output compared to PVDF under applied load. Furthermore, the BZT/PVDF composite demonstrated excellent stress tolerance and enhanced piezoelectric performance under varying loads. Notably, the BZT/PVDF composite showed impressive energy harvesting capabilities during finger tapping, storing electrical energy in capacitors, to power electronic watch, calculator, mini-speaker, and illuminating LEDs. The composite also exhibited potential for monitoring and harvesting energy from human motion. Additionally, BZT/PVDF was utilized as a smart lab alarm (SLA) system for the safety of human beings, enhancing safety in laboratories by signaling potential contact between BZT/PVDF and human beings in hazardous areas. These findings indicate the flexible BZT/PVDF composite as a promising solution for lead-free energy harvesting and self-powered smart IoT-based electronics.

Eliminating surface cracks in metal film-polymer substrate for reliable flexible piezoelectric devices

In a flexible piezoelectric-metal-polymer device, the occurrence of surface cracks in metal-polymer interface may cause unstable metal connections, unreliable piezoelectric yield, poor passivation behaviour and metal electrode delamination. In this study, the properties of polydimethylsiloxane (PDMS) polymer substrate are optimised, and the sputter-deposition of aluminium (Al) and molybdenum (Mo) metal film layer is controlled to eradicate cracks and promote only surface wrinkles on large area metal-polymer interface. The PDMS substrate thickness of ∼123.8 µm, 20:1 prepolymer base to curing agent weight ratio, 50 °C PDMS curing temperature and 30 min of Al sputtering time have been discovered to produce crack-free wrinkle-only Al thin film layer on PDMS substrate. The Al thin film is 100 % conductive over large area and adhere well on PDMS with 0 % of Al removal. The grown zinc oxide (ZnO) and aluminium nitride (AlN) piezoelectric layer on the improved Al-PDMS are of good crystal quality, generating low leakage current and decent piezoelectric voltage. The attained crack-free wrinkled-only metal film-polymer substrate interface is vital for flexible piezoelectric-metal-polymer device to perform well as an acoustic sensor, energy harvester, or even as an insulation/buffer layer in stretchable electronics.

Efficient energy harvesting enabled by large-area piezoelectric PVDF-based composite film enhanced by carbon nanotubes

Considerable attention has been drawn to the use of flexible piezoelectric energy harvesting devices for powering smart wearable technology. Herein, we employed a melt extrusion casting process to prepare large-area PVDF-based piezoelectric composite films and achieved continuous production. The films were prepared by adding 15 wt% lead zirconate titanate powder modified with a titanium coupling agent (PZT@UP15) and different content of carbon nanotubes (CNTs) exhibiting high conductivity into the PVDF matrix. The addition of CNTs in moderate amounts significantly enhanced the mechanical, dielectric, and piezoelectric properties of the composite films. Remarkably, the composite film containing 0.06 wt% CNTs achieved a d33 value of 28 pC/N, generated an open circuit voltage of 16.85 V, and a maximum power density of 0.46 μW/cm2 in the bending-releasing mode. Furthermore, the film exhibited relatively stable output performance even after 1500 cycles. The enhanced performances of the piezoelectric composite films can be attributed to the factors that the CNTs can effectively promote PVDF polarization by inducing dipole alignment and building an internal electric field, and further improve the piezoelectric performance and the electrostrictive performance. This work shows that the prepared piezoelectric composite film holds great potential as an energy harvesting device to provide power for wearable electronic devices.

Accurate finite element modeling of multilayered flexible piezoelectric energy harvesting devices with strong coupling of structure, piezoelectricity, and circuit

Multilayered flexible piezoelectric energy harvesting devices (FPEDs) are a new future harvesting technology which are highly flexible and lightweight than familiar cantilever piezoelectric energy harvesters. This mechanical vibration driven FPED is a strongly coupled multiphysics phenomena that involve complex natural three-way interaction among the composite piezoelectric structure, the electric charge accumulated in the piezoelectric material, and a controlling electrical circuit attached to it. Efficient and accurate computational solution approaches are essential for analyzing these mechanical vibration-driven FPEDs to capture the main physical aspect of the coupled phenomena and to accurately predict the output voltage. While there are some numerical models for simple familiar cantilever type piezoelectric energy harvester reported in the literature, a fully three-dimensional strongly coupled model for complex material distributed, complex geometry, and multilayered FPED involving strong coupling of structure, piezoelectricity, and circuit phenomena has not yet been developed. A partitioned iterative algorithm is developed using a hierarchical decomposition approach wherein the coupled three fields are solved separately and coupled through loop union integration techniques that provide an efficient and accurate simulation of FPEDs. The simulation results matched the experiment results very well. This study provides a basis for the natural extension of partitioned iterative finite element coupled algorithm to simulate the future piezoelectric energy harvesting technologies involving a strong coupling of structure, piezoelectricity, and circuit phenomenon.

Bottom Electrode Effects on Piezoelectricity of Pb(Zr0.52,Ti0.48)O3 Thin Film in Flexible Sensor Applications

Piezoelectric thin films grown on a mechanical, flexible mica substrate have gained significant attention for their ability to convert mechanical deformation into electrical energy though a curved surface. To extract the generated charge from the PZT thin films, bottom electrodes are typically grown on mica substrates. However, this bottom electrode also serves as a buffering layer for the growth of PZT films, and its impact on the piezoelectric properties of PZT thin films remains understudied. In this work, the effect of Pt and LaNiO3 bottom electrodes on the piezoelectric effect of a Pb(Zr0.52,Ti0.48)O3 thin film was investigated. It was observed that the PZT thin films on LNO/Mica substrate possessed weaker stress, stronger (100) preferred orientation, and higher remanent polarization, which is beneficial for a higher piezoelectric response theoretically. However, due to insufficient grain growth resulting in more inactive grain boundaries and lattice imperfections, the piezoelectric coefficient of the PZT thin film on LNO/Mica was smaller than that of the PZT thin film on a Pt/Mica substrate. Therefore, it is concluded that, under the current experimental conditions, PZT films grown with Pt as the bottom electrode are better suited for applications in flexible piezoelectric sensor devices. However, when using LNO as the bottom electrode, it is possible to optimize the grain size of PZT films by adjusting the sample preparation process to achieve piezoelectric performance exceeding that of the PZT/Pt/Mica samples.

Enhanced Piezoelectricity of PVDF-TrFE Nanofibers by Intercalating with Electrosprayed BaTiO3.

Over the past few decades, flexible piezoelectric devices have gained increasing interest due to their wide applications as wearable sensors and energy harvesters. Poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), as one of piezoelectric polymers, has caught considerable attention because of its high flexibility, high thermal stability, and biocompatibility. However, its relatively lower piezoelectricity limits its broader applications. Herein, we present a new approach to improving the piezoelectricity of PVDF-TrFE nanofibers by integrating barium titanate (BTO) nanoparticles. Instead of being directly dispersed into PVDF-TrFE nanofibers, the BTO nanoparticles were electrosprayed between the nanofiber layers to create a sandwich structure. The results showed that the sample with BTO sandwiched between PVDF-TrFE nanofibers showed a much higher piezoelectric output compared to the sample with BTO uniformly dispersed in the nanofibers, with a maximum of ∼ 457% enhancement. Simulation results suggested that the enhanced piezoelectricity is due to the larger strain induced in the BTO nanoparticles in the sandwich structure. Additionally, BTO might be better poled during electrospraying with higher field strength, which is also believed to contribute to enhanced piezoelectricity. The potential of the piezoelectric nanofiber mats as a sensor for measuring biting force and as a sensor array for pressure mapping was demonstrated.

Synergistic influence of surface‒modified SmxZn1-xCoO3‒poly(vinylidene fluoride) as a piezoelectric material for smart IoT applications

Due to the ability of mechanical energy converted to electrical energy, flexible piezoelectric energy harvesters have significant attention in recent years. In this current study, we designed and developed trimetallic oxide-based samarium zinc cobalt oxides, which were prepared using the co-precipitation method. The prepared material was fabricated using a solution casting method with 15% poly (vinylidene fluoride) (PVDF) to obtain a thin film of flexible piezoelectric sensor devices (FPSDs) SmxZn1-xCoO3/PVDF which was characterized by various analytical characterizations. Piezoelectrical characterizations were conducted on the fabricated (FPSDs) such as PVDF and SmxZn1-xCoO3/PVDF, by applying different dynamic forces. The obtained results clearly show that the output voltage of SmxZn1-xCoO3/PVDF improved, (33.3%) more than that of PVDF at 1 N force. Using finger tapping force on the surface of SmxZn1-xCoO3/PVDF FPSD to charge the capacitor, and it reached 245 mV within 16 s, then the light-emitting diodes (LEDs) glowed under amplification. Finally, the fabricated thin film was utilized to control the actions like the ‘jump’ of T-REX and ‘fly’ of flapping bird gaming interfaces using finger tapping. These optimistic results confirm that our fabricated FPSD is capable of energy-harvesting applications and self-powered smart IoT devices and so on.

Three-Dimensional Printable Flexible Piezoelectric Composites with Energy Harvesting Features.

The purpose of this work was to obtain an elastic composite material from polymer powders (polyurethane and polypropylene) with the addition of BaTiO3 until 35% with tailored dielectric and piezoelectric features. The filament extruded from the composite material was very elastic but had good features to be used for 3D printing applications. It was technically demonstrated that the 3D thermal deposition of composite filament with 35% BaTiO3 was a convenient process for achieving tailored architectures to be used as devices with functionality as piezoelectric sensors. Finally, the functionality of such 3D printable flexible piezoelectric devices with energy harvesting features was demonstrated, which can be used in various biomedical devices (as wearable electronics or intelligent prosthesis), generating enough energy to make such devices completely autonomous only by exploiting body movements at variable low frequencies.

Modulation of Electrical Characteristics of Polymer–Ceramic–Graphene Hybrid Composite for Piezoelectric Energy Harvesting

The use of lead-based ceramics to enhance the piezoelectricity of poly(vinylidene fluoride) (PVDF) is the primary challenge toward nontoxic flexible piezoelectric devices. 0.67BiFeO3-0.33BaTiO3 (BF33BT) is one of the lead-free piezoceramics with high-temperature stability and comparable piezoelectric characteristics to existing lead-based piezoceramics. The work represents PVDF–BF33BT two-phase and PVDF–BF33BT–graphene oxide (GO) three-phase composites with detailed analysis of the dielectric, ferroelectric, and piezoelectric characterizations. Solvent-casting followed by the hot-pressing technique improves the electroactive β-phase of ≥60% in the composites. With BF33BT and GO loading, the dielectric constant and loss tangent increase; however, there is an abrupt rise at the threshold GO concentration of 0.08 wt %. The three-phase composite with 40 wt % BF33BT and 0.08 wt % GO records a dielectric constant of 303 and a loss tangent of 0.68. The harvester out of the same composition achieves a piezoelectric strain constant of 9 pC·N–1, an open-circuit voltage of ∼3.9 V, and a short-circuit current of 1.3 μA. The feasibility of the harvester was tested by powering a calculator by charging a 2.2 μF capacitor after rectification. The recoverable energy density also improves seven times, indicating that the PVDF–BF33BT–GO composite is preferable for piezoelectric and energy storage applications.

A Flexible and Biodegradable Piezoelectric‐Based Wearable Sensor for Non‐Invasive Monitoring of Dynamic Human Motions and Physiological Signals

AbstractRecent progress in flexible sensors and piezoelectric materials has enabled the development of continuous monitoring systems for human physiological signals as wearable and implantable medical devices. However, their non‐degradable characteristics also lead to the generation of a significant amount of non‐decomposable electronic waste (e‐waste) and necessitate a secondary surgery for implant removal. Herein, a flexible and biodegradable piezoelectric material for wearable and implantable devices that addresses the problem of secondary surgery and e‐waste while providing a high‐performance platform for continuous and seamless monitoring of human physiological signals and tactile stimuli is provided. The novel composition of bioresorbable poly(l‐lactide) and glycine leads to flexible piezoelectric devices for non‐invasive measurement of artery pulse signals in near‐surface arteries and slight movement of the muscle, including the trachea, esophagus, and movements of joints. The complete degradability of piezoelectric film in phosphate‐buffered saline at 37 °C is also shown. The developed pressure sensor exhibits high sensitivity of 13.2 mV kPa−1 with a response time of 10 ms and shows good mechanical stability. This piezoelectric material has comparable performance to commonly used non‐degradable piezoelectric materials for measuring physiological signals. It can also be used in temporary implantable medical devices for monitoring due to its degradable nature.

Fabrication, Characterization, and Signal Processing Optimization of Flexible and Wearable Piezoelectric Tactile Sensors

Piezoelectric microelectromechanical systems (MEMS) meet the growing demand for sensors with small sizes and low power consumption. For tactile applications and pressure measurements, they are applied in various fields from robotics to healthcare. In this context, flexible devices are very important for their high responsivity and ability to conform to the analyzed surface. This work reports on miniaturized flexible and compliant piezoelectric devices to increase the number of integrable sensors for detecting and discriminating localized pressures and contacts per unit area with minimal crosstalk. For this purpose, a series of Aluminium Nitride-based (AlN) piezoelectric sensors with different diameters (from 5 μm to 500 μm) was realized and the generated electrical signal by sensor deformation was amplified by a differential voltage amplifier circuit. By the analysis of the shape of the piezoelectric signal as a function of the applied pressure, oscillations due to piezoelectric deformations, superimposed on the initial peak signal corresponding to the touch event, have been observed. The integral of the electrical signal was calculated for the most accurate representation to describe the sensor’s response. The best responsivity was obtained in samples with diameters of 200 μm and 500 μm. Furthermore, it was also found that the minimum distance between the edges of closed sensors, observing crosstalk below -20 dB, was around 500 μm.

Influence of the intermediate oxidation layer on the characteristics of lead zirconate titanate thin films with aluminium substrate

This paper presents a flexible piezoelectric device that has been realized by depositing lead zirconate titanate (PZT) thin films by chemical solution deposition (CSD) on a commercial aluminum foil as a substrate. The thermal treatment required for the crystallization of the PZT thin films leads to the oxidation of the substrate and a parasitic intermediate layer of alumina (Al2O3) is formed between the substrate and the first PZT layer. The comparison with and without the use of a conductive ruthenium dioxide (RuO2) interlayer, which can shunt the insulating alumina layer, showed the influence of the latter on the different characteristics of the material. The thickness of the alumina layer on the surface of the aluminum substrate after deposition of the PZT film (≈ 39 nm) was determined by calculation and confirmed by transmission electron microscopy (TEM). Dielectric characterization of the sample without considering this layer gives the permittivity of the Al2O3/PZT bilayer and not the active material alone (PZT). A relative permittivity value of 313 is measured against 558 for the single PZT layer if the alumina layer is taken into account, which means a decrease of 44%. The piezoelectric characterization is also influenced by the alumina layer, the piezoelectric coefficient is 14 pC/N while it is 26 pC/N when this layer is taken into account. This study evidences and quantitatively evaluates the influence of the oxidation layer (Al2O3) on the dielectric and piezoelectric characteristics and mechanical energy harvesting performances.

Multi-material freeform 3D printing of flexible piezoelectric composite sensors using a supporting fluid

Three-dimensional (3D) printed flexible piezoelectric devices featuring conformal or freeform geometries show great potential for being fabricated into wireless sensors and energy harvesters with tailorable mechanical stiffness and piezoelectric response. In our work, supporting fluid-assisted multi-material extrusion-based 3D printing technology has been successfully utilized to fabricate flexible conformal or freeform piezoelectric composite sensors with integrated electrodes. The printing technique relies on the extrusion of two paste-like materials: piezoelectric and conductive composite inks. A comprehensive characterization of the inks (i.e., piezoelectric or conductive behaviors, rheological and mechanical properties) and the rheological behavior of the supporting fluid are performed. Polydimethylsiloxane (PDMS)/30 vol% lead zirconate titanate (PZT), PDMS/25 vol% silver (Ag) and mineral oil/6% (w/v) fumed silica are the formulations for piezoelectric ink, conductive ink and supporting fluid, respectively. Three types of piezoelectric composite demonstrators which are a multi-layer planar film, a conformal non-planar hemisphere and a 3D structure composed of six spirals printed vertically between two hexagon layers (freeform spiral-hexagon), are fabricated and tested under tension or compression tests. The piezoelectric performance is consistent with the applied stress in all the tests. For example, the freeform spiral-hexagon piezoelectric sensor has a peak-to-peak voltage output of 86.39 ± 1.145 mV when it is subjected to a cyclic compression force at 8 Hz for more than 800 cycles. The dimensional accuracy measurements using an optical microscope and the microstructure images taken using a scanning electron microscope (SEM) show that the fabricated 3D structures have good shape fidelity (with a maximum relative error of ~3.5%) when compared to the designed models. Our fabrication approach opens a new way to fabricate conformal and freeform piezoelectric structures with integrated electrodes from flexible composites for sensing and energy harvesting applications.

Inch-Size Molecular Ferroelectric Crystal with a Large Electromechanical Coupling Factor on Par with Barium Titanate.

Molecular ferroelectrics with large piezoelectric responses have long been sought for their advantages of light weight, mechanical flexibility, and easy preparation, in contrast to the widely used inorganic counterparts. Representatively, a molecular ferroelectric crystal [Me3NCH2Cl]CdCl3 (TMCM-CdCl3) has been found to show a large piezoelectric coefficient d33 of 220 pC/N exceeding that of BaTiO3 (You et al. Science2017, 357, 306-309). However, although the d33 of molecular ferroelectrics has achieved great progress, their electromechanical coupling factor k33, which is essential for various piezoelectric applications, including ultrasonic transducers and actuators, was rarely explored and is far below the level of inorganic ferroelectrics. The major reason for this situation is the great challenge of growing large-size crystals which is a key limiting factor for measuring k33. Here, we grew inch-size crystals of organic-inorganic perovskite ferroelectric TMCM-CdCl3 with a high d33 (383 pC/N) for investigating its piezoelectric responses including the k33 (0.483) by the resonance method. Such high k33 (0.483) is much larger than those of other molecular ferroelectrics and competitive with that of BaTiO3 (0.5). In addition, TMCM-CdCl3 has a low elastic modulus of 13.03 GPa, an order of magnitude lower than that of BaTiO3. This finding sheds light on the exploration of large electromechanical coupling factors in molecular ferroelectrics for potential applications in flexible and portable piezoelectric devices.

A Flexible Piezoelectric Device for Frequency Sensing from PVDF/SWCNT Composite Fibers.

Polymer piezoelectric devices have been widely studied as sensors, energy harvesters, and generators with flexible and simple processes. Flexible piezoelectric devices are sensitive to external stimuli and are attracting attention because of their potential and usefulness as acoustic sensors. In this regard, the frequency sensing of sound must be studied to use flexible piezoelectric devices as sensors. In this study, a flexible piezoelectric device composed of a polymer and an electrode was successfully fabricated. Polyvinylidene fluoride, the active layer of the piezoelectric device, was prepared by electrospinning, and electrodes were formed by dip-coating in a prepared single-walled carbon nanotube dispersion. The output voltage of the external sound was matched with the input frequency through a fast Fourier transform, and frequency matching was successfully performed, even with mechanical stimulation. In a high-frequency test, the piezoelectric effect and frequency domain peak started to decrease sharply at 300 Hz, and the limit of the piezoelectric effect and sensing was observed from 800 Hz. The results of this study suggest a method for developing flexible piezoelectric-fiber frequency sensors based on piezoelectric devices for acoustic sensor systems.

Experimental and numerical studies on working parameter selections of a piezoelectric-painted-based ocean energy harvester attached to fish aggregating devices

Fish aggregating devices (FADs) have not only greatly improved the fishing capacity in recent years, but also play an important role in marine monitoring and data collection. In this study, a flexible piezoelectric device (FPED) for ocean energy harvesting was designed to achieve continuous and stable energy supply for FAD equipments and islands. Firstly, we developed FPEDs coated with piezoelectric paint. Painted FPEDs were then attached to the frame of an FAD to examine their characteristics including submerged depth and the support-type. Moreover, under broadband wave conditions, we investigated the dominant parameters influencing electrical performance. Furthermore, we built a theoretical model according to the experiment setup and developed a computational model based on the immersed boundary method to evaluate the FPED-wave interactions. Both the theoretical and computational results were validated by experimental ones, demonstrating that the two models can be considered as alternative tools in FPED working parameter selections. Finally, we conducted a field test under real sea conditions with a remote data monitoring system for the painted FPEDs, which showed good performance under extreme bending, weathering, and fatigue.

Novel Rubber Composites Based on Copper Particles, Multi-Wall Carbon Nanotubes and Their Hybrid for Stretchable Devices.

New technologies are constantly addressed in the scientific community for updating novel stretchable devices, such as flexible electronics, electronic packaging, and piezo-electric energy-harvesting devices. The device promoted in the present work was found to generate promising ~6V and durability of >0.4 million cycles. This stretchable device was based on rubber composites. These rubber composites were developed by solution mixing of room temperature silicone rubber (RTV-SR) and nanofiller, such as multi-wall carbon nanotube (MWCNT) and micron-sized copper particles and their hybrid. The hybrid composite consists of 50:50 of both fillers. The mechanical stretchability and compressive modulus of the composites were studied in detail. For example, the compressive modulus was 1.82 MPa (virgin) and increased at 3 per hundred parts of rubber (phr) to 3.75 MPa (MWCNT), 2.2 MPa (copper particles) and 2.75 MPa (hybrid). Similarly, the stretching ability for the composites used in fabricating devices was 148% (virgin) and changes at 3 phr to 144% (MWCNT), 230% (copper particles) and 199% (hybrid). Hence, the hybrid composite was found suitable with optimum stiffness and robust stretching ability to be useful for stretching electronic devices explored in this work. These improved properties were tested for a real-time stretchable device, such as a piezoelectric energy-harvesting device and their improved voltage output and durability were reported. In the end, a series of experiments conducted were summarized and a discussion on the best candidate with higher properties useful for prospective applications was reported.

Screen Printing of Surface-Modified Barium Titanate/Polyvinylidene Fluoride Nanocomposites for High-Performance Flexible Piezoelectric Nanogenerators.

Piezoelectric energy harvesters are appealing for the improvement of wearable electronics, owing to their excellent mechanical and electrical properties. Herein, screen-printed piezoelectric nanogenerators (PENGs) are developed from triethoxy(octyl)silane-coated barium titanate/polyvinylidene fluoride (TOS-BTO/PVDF) nanocomposites with excellent performance based on the important link between material, structure, and performance. In order to minimize the effect of nanofiller agglomeration, TOS-coated BTO nanoparticles are anchored onto PVDF. Thus, composites with well-distributed TOS-BTO nanoparticles exhibit fewer defects, resulting in reduced charge annihilation during charge transfer from inorganic nanoparticles to the polymer. Consequently, the screen-printed TOS-BTO/PVDF PENG exhibits a significantly enhanced output voltage of 20 V, even after 7500 cycles, and a higher power density of 15.6 μW cm−2, which is 200 and 150% higher than those of pristine BTO/PVDF PENGs, respectively. The increased performance of TOS-BTO/PVDF PENGs is due to the enhanced compatibility between nanofillers and polymers and the resulting improvement in dielectric response. Furthermore, as-printed devices could actively adapt to human movements and displayed excellent detection capability. The screen-printed process offers excellent potential for developing flexible and high-performance piezoelectric devices in a cost-effective and sustainable way.