Piezoelectric Polyvinylidene Fluoride Film Research Articles

Improved Surface-Enhanced Raman Scattering Performance of 2D Ti3C2Tx MXene Embedded in PVDF Film Enabled by Photoinduction and Electric Field Modulation.

In this study, we introduce a synergistic approach to enhance the surface-enhanced Raman scattering (SERS) signal in two-dimensional (2D) MXene through photo-irradiation and electric field modulation. Our methodology involves the integration of 2D Ti3C2Tx MXene with piezoelectric polyvinylidene fluoride (PVDF) polymer, resulting in the creation of a free-standing, flexible composite film. On this composite film, a thin layer of Au was deposited. Our flexible substrate was able to sense methylene blue (MB), crystal violet (CV), 4-aminothiophenol (ATP), and melamine. The SERS substrate exhibits low detection limit of 10-8 M MB with a 6.7 × 106 enhancement factor (EF). The SERS substrate enables picomolar (pM) detection sensitivity for CV molecules with an EF of 9.2 × 109. Furthermore, the introduction of photo-irradiation leads to an additional ∼3.5-fold enhancement in the SERS signal, which is attributed to the altered work function and defects. The application of mechanical force to the piezoelectric PVDF/Ti3C2Tx film results in a ∼4.5-fold boost in SERS signal due to mechanical force-induced electrical energy. The fabrication strategy employed here for producing a flexible piezoelectric PVDF/Ti3C2Tx film holds significant promise for expanding the potential application of 2D MXene in rapid, on-site sensing scenarios.

Experimental study of taper shape bistable beam for improved vibration energy harvesting

Unwanted vibrations cause discomfort and affect the accuracy of the machinery. Vibrations of low frequency (<30 Hz) are usually inutile. Various researchers focus on harvesting and enhancing energy output through low-frequency vibrations. This paper focuses on improving energy harvesting from low-frequency vibration sources through taper shape (TAP) bistable beam fabricated using thin Piezoelectric Polyvinylidene fluoride (PVDF) film sandwiched between thin copper and aluminium films on both sides. Voltage power output through a PVDF film depends on the film’s strain distribution; hence, in this study, five different beam designs are studied for strain distribution through the ANSYS workbench. Further, an experimental harmonic analysis study for voltage output is performed on rectangular beam (RECT) and TAP beam for both straight and bistable configuration using three different harmonic input conditions, which concluded that the voltage output for the TAP beam is much more than that of the RECT beam, with a much more significant voltage output increase in bistable conditions for all three harmonic input conditions.

Energy harvesting from low-frequency vibrations of hanger using PVDF: An experimental study and performance analysis

Piezoelectric energy harvesters (PEH) are widely used to collect piezoelectric energy. However, adapting to different engineering application environments is difficult for traditional PEHs. To improve the engineering application value of PEH, a hanger piezoelectric energy harvester (HPEH) based on low frequency vibration of hanger is proposed in this paper. A dynamic electromechanical coupling model was established for hanger structure, and the effects of the external load resistance, the polyvinylidene fluoride (PVDF) piezoelectric film installation location, the stability of the PVDF piezoelectric film with different winding methods, and the external excitation amplitude on the energy output performance of the HPEH were studied. Results indicate that the optimal load resistance of the HPEH studied in this paper is 1.0 MΩ; the PVDF piezoelectric film location has a significant impact on the performance of the HPEH, and the output power is highest at hanger Lc/4; the PVDF piezoelectric films during ring winding is better than those in spiral winding for the same external cycle excitation; in the external excitation amplitude range of 2d–6d (d: hanger diameter), appropriately increasing the external excitation amplitude is conducive to improving the output voltage of the HPEH, with the root mean square voltage increasing by 95.11 % at external excitation amplitude A = 6d compared with that at the initial excitation amplitude. It provides an innovative solution for the field of cable structures and new energy sources, and the further research and application of this technology is expected to have a profound impact in the field of energy sustainability and engineering technology.

Enhanced energy harvesting ability of bismuth sodium titanate/polyvinylidene fluoride composite film-based piezoelectric nanogenerators for mechanical energy scavenging and safety-walker applications

Herein, we proposed a piezoelectric Bi0.5Na0.5TiO3 (BNT)/polyvinylidene fluoride (PVDF) flexible composite film-based peizoelectric nanogenerator (PNG) device as a highly efficient mechanical energy harvester. Initially, the BNT nanoparticles (NPs) with high dielectric constant were synthesized and loaded into a PVDF polymer matrix. The effect of BNT loading on the chemical property, dielectric property, and β phase of PVDF-based composite films was analyzed in depth. The various PNG devices based on the PVDF piezoelectric films with different concentrations of BNT NPs and aluminum electrodes were fabricated. The external force was applied to all the PNGs and their electrical output was systematically investigated to find the optimal concentration of BNT NPs inside the PVDF. The optimized 0.5 wt% BNT loaded PVDF composite film-based PNG device produced a highly efficient electrical output of about 19 V, 1.2 μA, and 3.5 mW/m2. The fabricated PNG device was robust and could generate highly stable electrical output over a long period. A highly efficient external electrical circuit was developed to effectively store the generated electricity from the PNG into various energy storage devices. Furthermore, the generated electrical energy was utilized to charge various energy storage capacitors and to power small electronics. Additionally, the flexible PNG device was demonstrated as a biomechanical energy harvester to convert various human movements into electricity successfully. Owing to the high flexibility, robustness, and energy conversion efficiency of the fabricated PNG device, it is expected to be utilized to harvest various mechanical movements available in daily life through large-scale technology. The unique PNG-powered self-illuminating bracelet-based safety walker system was proposed, which can be utilized in daily life to avoid accidents on roads and for many other applications.

Magnetic Modulation of the Piezoelectric Polyvinylidene Fluoride Film Energy Harvester for Noncontact Dynamic Characteristics Control

This paper aims to improve the performance of the piezoelectric buckled beam under low vibration environment using the noncontact magnetic modulation method. Based on the bi-stable buckling beam structure, the magnetic force is introduced to capture more energy. In order to investigate the influence of magnetic force in the process of vibration, the dynamic response of the harvester is analyzed under different magnetic force through numerical simulation and experiment. It is found that the magnetic force has a softening effect on the structure, namely, it could reduce the stiffness of the buckled beam. Therefore, the energy harvester could realize large-amplitude vibration under low-amplitude or low-frequency vibration with the help of magnetic force. The experimental results show that the harvester can realize inter-well vibration only when the vibration acceleration is 3.5[Formula: see text]g and the frequency is 15[Formula: see text]Hz without the magnetic force. The harvester only needs 2.5[Formula: see text]g acceleration or 10[Formula: see text]Hz vibration frequency to realize the large-amplitude vibration. While in the case of 12[Formula: see text]mm magnetic gap. After the magnetic force is introduced in the harvester, the voltage output under 2.5[Formula: see text]g acceleration is increased from 1 to 4[Formula: see text]V, and the voltage output at 10[Formula: see text]Hz vibration frequency is increased from 0.2 to 2[Formula: see text]V. Therefore, the proposed magnetically tuned bi-stable energy harvester can better operate in low frequency and low amplitude environments.

Design and Experimental Evaluation of a Dual-Cantilever Piezoelectric Film Sensor with a Broadband Response and High Sensitivity.

Cantilever-beam-type PVDF (Polyvinylidene Fluoride) piezoelectric film sensors are commonly utilized for vibration signal detection due to their simple structures and ease of processing. Traditional cantilevered PVDF piezoelectric film sensors are susceptible to the influence of the second-order vibration mode and have a low lateral stress distribution at the free end, which limit their measurement bandwidth and sensitivity. This study is on the design of a dual-cantilever PVDF piezoelectric film sensor based on the principle of cantilevered piezoelectric film sensors. The results of the experiments indicate that, compared to a typical single-arm piezoelectric cantilever beam vibration sensor, the developed sensor has a longer second-order natural frequency that ranges from 112 Hz to 453 Hz, while the first-order natural frequency is maintained at around 12 Hz. This leads to a better ratio of the second-order natural frequency to the first-order natural frequency and a wider frequency response range. At the same time, the sensitivity is increased by a factor of 3.48.

Surface Crack Monitoring by Rayleigh Waves with a Piezoelectric-Polymer-Film Ultrasonic Transducer Array.

This paper presents a method for measuring surface cracks based on the analysis of Rayleigh waves in the frequency domain. The Rayleigh waves were detected by a Rayleigh wave receiver array made of a piezoelectric polyvinylidene fluoride (PVDF) film and enhanced by a delay-and-sum algorithm. This method employs the determined reflection factors of Rayleigh waves scattered at a surface fatigue crack to calculate the crack depth. In the frequency domain, the inverse scattering problem is solved by comparing the reflection factor of the Rayleigh waves between the measured and the theoretical curves. The experimental measurement results quantitatively matched the simulated surface crack depths. The advantages of using the low-profile Rayleigh wave receiver array made of a PVDF film for detecting the incident and reflected Rayleigh waves were analyzed in contrast with those of a Rayleigh wave receiver using a laser vibrometer and a conventional lead zirconate titanate (PZT) array. It was found that the Rayleigh waves propagating across the Rayleigh wave receiver array made of the PVDF film had a lower attenuation rate of 0.15 dB/mm compared to that of 0.30 dB/mm of the PZT array. Multiple Rayleigh wave receiver arrays made of the PVDF film were applied for monitoring surface fatigue crack initiation and propagation at welded joints under cyclic mechanical loading. Cracks with a depth range of 0.36-0.94 mm were successfully monitored.

Dynamic characteristics of axial load bi-stable energy harvester with piezoelectric polyvinylidene fluoride film

In this paper, a nonlinear bi-stable energy harvester with a bulking beam is proposed. Its bi-stable characteristics can be realized by the structure. The characteristics of the piezoelectric energy harvester are tested under different conditions. In the experiment, high speed framing camera is used to capture the details of movement. It is found that similar characteristics occur at low frequency and high frequency, but the principles are not the same. The vibration amplitude is insufficient former when the frequency is low. Under high frequency conditions, the system is hindered by the reverse excitation when the system is about to enter the second steady state due to insufficient response time. In the experiment, the axial load is measured by the length of the buckling beam and the electronic scale. It is found that the axial load has great influence on the vibration amplitude of the harvester. The results show that the harvester changes from inter-well vibration to intra-well vibration when axial load changes from 0.4 N to 1.5 N. The inter-well vibration of the harvester occurs when the acceleration is 3.5 g, the vibration frequency is 15 Hz and the axial load is 0.4 N.

Vibration Energy Conversion Power Supply Based on the Piezoelectric Thin Film Planar Array.

Vibration energy harvesting has received much attention as a new type of power solution for low-power micro/nano-devices. However, VEH (vibration energy harvester) based on PVDF (polyvinylidene fluoride) piezoelectric materials have a low output power and energy conversation efficiency due to the relatively low piezoelectric constant, coupling coefficient, and dielectric constant. For this reason, we design a vibration energy conversion power supply, which consists of a VEH with a PVDF piezoelectric thin film planar array vibration structure and an energy harvesting circuit for regulating the electric energy of multiple sources. Furthermore, our solution was validated by simulations of structural dynamics in COMSOL and equivalent circuits model in Multisim. From the circuitry simulation results, the output current and the charging period increase and decrease, doubling, respectively, for each doubling of the number of array groups of films. Moreover, the solid mechanics simulation results show that the planar array structure makes the phase and amplitude of the input vibration waves as consistent as possible so that the same theoretical enhancement effect of the circuitry model is achieved. An identical experimental test was implemented with vibration conditions of 75 Hz-2.198 g. The fabricated harvester quickly charged the 22 V-0.022 F ultracapacitor bank to 5 V in 24 min. The maximum open circuit voltage and output power, respectively, were 10.4 V and 0.304 mW. This maximum charging power was 11.69 times higher than that of a single film. This special power supply can replace batteries to power low-power electronics deployed in vibrating environments, thus reducing the maintenance costs of equipment and environmental pollution rates.

Improved surface-enhanced Raman scattering performance enabled by hydrophilic-hydrophobic piezoelectric PVDF-silver substrate

It holds extreme significance in expansive fields to promote the sensitivity and quantitative aptitudes of surface-enhanced Raman scattering (SERS) substrate. Herein, a distinctive piezoelectric polyvinylidene fluoride (PVDF) film combined with hydrophilic-hydrophobic strategy was ventured into SERS technique to facilitate a superior self-energized hybrid substrate. Notably, enhanced localized electromagnetic field of Ag nanoparticles (Ag NPs) could be rationally induced by pressing or bending the PVDF film, enabling a tunable ultra-high sensitivity. The quantitative level of the sensitive detection was further improved by employing a facile hydrophilic-hydrophobic strategy to uniformly anchor and enrich analytes, ascertaining a low variation of 11.8%. As a proof-of-concept, an in-situ collection and assay of enrofloxacin residue on fishes with different surface roughness were successfully accomplished by the pressed substrate and trustworthy recovery rates were demonstrated. Briefly, the hydrophilic-hydrophobic self-energized PVDF-Ag hybrids demonstrated superior SERS enhancement with a promising uniformity, providing a novel and practical design options for sensing devices and facilitating the noninvasive monitoring of residue in sea food. • A novel kind of self-energized E-SERS substrate with a tunable ultra-high sensitivity was developed. • An facile hydrophilic-hydrophobic strategy was used to improve the accuracy of the E-SERS signal. • A practical monitoring of enrofloxacin residue on fishes was achieved by the self-energized substrate.

Analysis of space debris impact source localization based on PVDF piezoelectric film

As the pace of human exploration and utilization of space continues to accelerate, space debris gradually becomes an inevitable problem affecting and threatening human space activities. When space debris strikes the spacecraft bulkhead, determining the impact source location timely and accurately is the foundation of the repair damage, and is also of great importance for the safety of astronauts' life. This paper analyzed the wave propagation law in thin plates, established a lightweight sensor array using PVDF (Polyvinylidene fluoride) circular thin-film sensors, and used a two-stage light-gas gun loading system to conduct hypervelocity collision localization experiments on impacting 2A12 aluminum plates to study the effects of sensor array radius and sensor size on localization results. The results show that the smaller the radius of the PVDF sensor array is, the more accurate the positioning result is under the premise of the same size of the PVDF circular film sensor array. On the premise of the same PVDF sensor array arrangement, the larger the PVDF circular membrane sensor is, the more accurate the positioning result is. ABAQUS finite element software is used to study the stress wave propagation of aluminum ball impacting aluminum plate at high speed, simulating space debris impacting spacecraft. The stress waveform obtained from the simulation is in good agreement with the experiment, which shows the accuracy of the numerical simulation method.

On-line monitoring of steel ball stamping by mechatronics cold heading equipment based on PVDF polymer sensing material

Abstract In order to explore the influence of cold heading equipment based on polyvinylidene fluoride (PVDF) polymer sensing material on steel ball stamping, a new method was proposed to reflect the defects of cold heading forming of steel ball by load signal. PVDF piezoelectric film is used as the sensor design of force and support structure of steel ball cold heading electromechanical sensor model. PVDF piezoelectric thin film force sensor is used for the structural optimization and simulation. The structural parameters affecting the natural frequency are numerically analyzed by MATLAB software. The mapping relationship between the external load and the output load of the sensor is obtained by using ANSYS software, and the simulation curve of the natural frequency of the sensor is compared with the theoretical curve to verify the factors affecting the natural frequency. The results show that the nonlinear error of sensors refers to the measured curve and the maximum deviation between the fitting line and the percentage of full-scale output.

Experimental investigation into the sensitivity of elastically coated piezoelectric polyvinylidene fluoride films to an impact force

This paper presents an experimental study on the effect of an elastic coating on the sensitivity to an impact force on a polyvinylidene fluoride (PVDF) film by using a model consisting of a top mass, a coated/uncoated PVDF film, and a base block. The sensitivity of the PVDF film is determined by measuring the voltage outputs from the PVDF film and an impact hammer, which is used to excite the top mass. The effects of the constraints at the top and bottom surfaces of an uncoated PVDF film on the sensitivity are examined first. Experimentally, the shear-free and perfectly bonded constraints are approximated by applying oil and epoxy glue to the interfaces between the PVDF film and the top mass/base block. The sensitivities of the PVDF film for these two constraints are determined analytically, thus explaining the roles of the stress components in the thickness and in-plane directions of the film in generating the voltage outputs. The approximated shear-free boundary condition using oil at the interface allows an experimental determination of the piezoelectric voltage constant of the PVDF film in the poling direction. Rubber and polyurethane are used for constructing the coated PVDF films. Even a thin layer of elastic coating is capable of significantly increasing the sensitivity of the PVDF film. For example, 3 mm rubber layers allow a 27 dB increase in the low-frequency sensitivity. A system including an elastically coated PVDF film provides an additional 10 dB increase at frequencies close to its first resonance frequency, resulting in a total 37 dB increase in the system sensitivity. The increased sensitivity may be explained as being due to the increased shear force between the elastic material and PVDF film as the thickness of the elastic layer increases. The dominating effect of the shear force is illustrated by the experimental and finite-element analysis as the thickness of the rubber coating gradually increases. The high rate of increase of the sensitivity as a function of rubber thickness can be observed when the thickness is under 0.8 mm.

A bionic piezoelectric tactile sensor for features recognition of object surface based on machine learning.

Based on the tactile mechanism of human fingertips, a bionic tactile sensor fabricated from polyvinylidene fluoride piezoelectric film is proposed, which can identify the surface softness, viscoelasticity, thermal conductivity, and texture roughness of the object. The tactile sensor is mounted on the fingertip of the bionic manipulator, which obtains the surface features by touching and sliding the object. The time-domain features of the output signal are used for preliminarily discriminating the softness, viscoelasticity, and heat conduction of the object. Finally, based on the Back Propagation and the Particle Swarm Optimization-Back Propagation neural network algorithm, the recognition experiment of texture roughness is carried out using the PSO algorithm to improve the BP neural network so that the optimized BP algorithm has a higher convergence accuracy. The results show that the PSO-BP algorithm achieved the highest accuracy of 98% for identifying samples with different roughnesses and the average recognition achieved an accuracy of 94%. The bionic piezoelectric tactile sensor proposed in this paper has a good application development prospect in recognizing the surface features of objects and intelligent robots.

Damage identification for a beam structure based on a PVDF piezoelectric film combined sensor

The structural strain curvature mode is widely used in structural health monitoring because of its high sensitivity to local changes and accurate damage localization capability. In this research, a combined polyvinylidene fluoride (PVDF) sensor was designed and manufactured based on measurement characteristics of the PVDF sensor. The designed sensor can directly measure the response signal of the strain difference in the structure. According to the central difference principle, the measured value is deduced and used to obtain the local strain curvature of the structure, and the strain curvature modal parameters of the structure are identified with the operating modal identification method. Taking the strain curvature mode shape difference as the damage index, the damage recognition results of the single-chip PVDF sensor and the combined PVDF sensor are compared by performing single damage, multiple damage and damage range experiments on a beam structure. The experimental results show that the combined PVDF sensor proposed in this study is more sensitive to local minor damage.

Electroprinting of MWCNT-assisted PVDF thin films with enhanced electrical properties

Polyvinylidene fluoride(PVDF) thin film with good electrical properties is usually used as a piezoelectric sensor or energy harvesting device. It has a broad potential application prospect in the fields of damage detection, structural vibration, medical devices, and artificial intelligence. In the work, PVDF/MWCNTs thin films were prepared by electroprinting method. The effect of the intercalation of MWCNTs on the β-PVDF formation and the mechanism of improving the electrical properties of PVDF piezoelectric thin films in the electroprinting process were discussed. The results show that the doping of MWCNTs promotes the crystallinity and the β-phase content of PVDF films in the electric field. With the increase of the amount of MWCNTs added, the piezoelectric and dielectric properties of the PVDF/MWCNTs thin film are correspondingly improved. However, the dielectric loss of the film is reduced. Due to the preparation and polarization of the film in the electroprinting process are unified, the PVDF piezoelectric film without poling shows excellent piezoelectric and dielectric properties.

Human Pulse Signal Acquisition System Based on PVDF Piezoelectric Film

Nowadays, traditional Chinese medicine (TCM) is attracting more attention. As the most complete methods of pulse diagnosis, the method named ‘three regions nine subdivisions’ has come to the fore. It is important to collect accurate pulse signals in this way. Hence a pulse signal acquisition system is developed, which includes a pulse sensor based on PVDF (Polyvinylidene fluoride) piezoelectric film, charge amplifier, low-pass filter, voltage amplifier, voltage follower, and a software system based on LabVIEW for controlling the acquisition process and storing data. And PVDF piezoelectric film has suitable performance for this system which as a new kind of polymer piezoelectric material. Finally, the experiment results demonstrate that the system can extract effective pulse signals without heavy pressure, laying a solid foundation for the subsequent analysis on pulse signals.

Experimental Studies on Fretting Wear Behavior of PVDF Piezoelectric Thin Films.

This paper discusses an in-depth experimental study on the fretting wear behavior of PVDF (polyvinylidene fluoride) piezoelectric thin film against a Si3N4 ceramic sphere under air conditions. A fretting wear device with a ball-on-plate contact configuration was applied. The changes of displacement amplitude, normal force, and applied voltage were taken into account. The friction logs were used to determine the contact state of the PVDF thin film during the fretting test. The 3D topography instrument and scanning electron microscope (SEM) were used to measure the details of the surface morphology and wear volume. The test results of PVDF thin films under different normal force, displacement amplitude, and applied voltage are summarized through the collection and analysis of experimental data. It is shown that the creep and plastic deformation lead to obvious winkles at the contact surface, which may decrease the specific wear rate of PVDF thin films.

Measurement Method for Fluid Pressure Fluctuation in Fluid-Conveying Pipe Using PVDF Piezoelectric Film Sensor

As a representative fluid-transporting system, fluid-conveying pipes play an essential role in many fields. For a fluid-conveying pipe system in operation, fluid pulsation in pipes contains much information about fluid flow parameters (flow velocity, fluid pressure, etc.). Therefore, the measurement of fluid pulsation is important for understanding the internal fluid flow. To use polyvinylidene fluoride (PVDF) piezoelectric film sensors to indirectly measure the pressure fluctuation of the internal fluid, we simulated a fluid-conveying pipe with PVDF piezoelectric film sensors attached to the outer pipe wall. The simulation results showed that the variation of voltage signal of PVDF, circumferential stress and strain of the pipe wall, and the pressure fluctuation of internal fluid were highly positively correlated, which proved that the PVDF piezoelectric film sensor can be applied to indirectly measure the pressure fluctuation of internal fluid. We also studied the influences of flow velocity pulsation and mechanical vibration caused by the pipeline pump during operation. It is found that the flow velocity pulsation had little influence on the measurements of the variation of circumferential stress and strain of the pipe wall and the internal fluid pressure fluctuation. When both ends of the pipe were fixed by hoops, mechanical vibration had little influence on the measurement of the variation of circumferential stress and strain of the pipe wall as well as the fluid pressure fluctuation. Finally, simulation results were verified by experiments.

Design, Assembly and Testing of a Novel Piezoelectric Geophone Based on PVDF Film

A piezoelectric geophone is a vibration transducer that converts mechanical vibrations into electrical signals via the piezoelectric effect. At present, the commonly used sensitive component of the conventional piezoelectric geophone is piezoelectric ceramic (PZT) material, which has low structural flexibility and high natural frequency. This paper reports a piezoelectric geophone based on polyvinylidene fluoride (PVDF) film with a sensitive unit composed of PVDF film and spiral cantilever beam, which can increase the sensitivity and reduce the low-frequency cutoff frequency. Firstly, the PVDF piezoelectric film is introduced, and the sensitive unit with PVDF piezoelectric film and spiral cantilever beam is designed. Secondly, the signal conditioning circuit and the digital module circuit are designed according to the characteristics of the detector and the test environment. Finally, the performance tests and fabrication of the geophone are carried out. The results indicate that the piezoelectric geophone has a stable sensitivity of 230 mV/m/s2 in the range of 4–90 Hz, which are superior to the existing piezoelectric geophone.