PVDF Piezoelectric Film Research Articles

Identification of Damage Mode of High-speed Impact Target Based on PVDF Piezoelectric Film

Identification of Damage Mode of High-speed Impact Target Based on PVDF Piezoelectric Film

Design of Multifunctional Touch and Slip Sensor System Based on PVDF Piezoelectric Film

A multi-functional touch slip sensing system is designed based on PVDF piezoelectric film. The piezoelectric sensor converts the pressure signal into electrical signal through piezoelectric effect, and the conditioning circuit further processes the electrical signal. After A/D conversion, the data is transferred to the upper computer to extract the information. In addition, based on the thermoelectric effect of piezoelectric film, the sensor can detect the thermal sensation signal and has the function of self-protection. The piezoelectric sensor adopts bionic fingerprint structure, which has high sensitivity and good flexibility. The conditioning circuit includes amplifying unit, filtering unit, voltage lifting unit and voltage following unit. These units are integrated on the circuit board of 11mm*10mm, which has high integration and easy application. The experiment verifies that manipulator equipped the sensing system can automatically judge tactile, slip and thermal sensation, and can grasp an egg and a paper cup with water, realizing the ability of soft grasping.

Research on mathematical model of characteristic curve of surface perception by PVDF array based on Ferguson function

The traditional 3D shape perception and reconstruction requires the use of relatively expensive 3D scanning equipment to obtain the coordinates of discrete feature points of the 3D shape. The reconstruction accuracy is determined by the scanning accuracy of the 3D scanning device, generally, the accuracy is low. In this study, based on the PVDF piezoelectric film sensing array, the 3D topographic feature point coordinate value is perceived and acquired. According to the feature point coordinate value, the feature curve fitting of the 3D shape is obtained, and the slope information of the 3D topography characteristic curve is obtained. The mathematical model of the feature surface of PVDF array surface topography based on Ferguson curve is studied to realise the surface reconstruction of 3D complex topography. Theoretical research shows that three-dimensional complex topographic reconstruction technique based on Ferguson curve for PVDF piezoelectric film array surface topography perception has the advantages of simple principle, easy implementation and high precision of shape reconstruction. It can develop intelligent structure with three-dimensional complex shape perception function.

Design and development of monitoring device for corn grain cleaning loss based on piezoelectric effect

It is wildly known that the grain direct harvest can improve the corn harvest efficiency effectively. However, in the process of grain direct harvest, incomplete threshing and cleaning loss will lead to the loss of corn grain. Among them, the grain loss caused by the cleaning process can be controlled and reduced by adjusting the opening extent of the cleaning sieve, fan speed and other parameters. In traditional operation process, the operator had to adjust the cleaning mechanism based on their experience, which directly leads to low efficiency as well as high rate of grain loss. The grain loss rate sensor proposed in this paper provides the feedback parameters to control the above actuators, which makes the intelligent cleaning of the harvester possible. By comparing the existing research results, the PVDF piezoelectric film was used as the sensitive material. A sensor test platform and a real machine test platform were built and the corresponding software system of the sensor was designed and developed. The software system includes data acquisition module, filtering algorithm, wave shaped module, counting module, data processing module and wireless transmission module. Moreover, an algorithm was proposed to calibrate the error caused by misidentification of the grains and residues. After the testing and debugging, the final identification error of the laboratory tests was decreased from 12% to 3% and the error of the real machine test was under 6%, which is acceptable.The research results of this paper provided the basis for the development of intelligent control system of grain harvesting machinery, and it is of great significance to reduce the cleaning loss rate of harvesting machinery.

Three-Dimensional MOF-Assisted Self-Polarized Ferroelectret: An Effective Autopowered Remote Healthcare Monitoring Approach.

In recent years, flexible and sensitive pressure sensors are of extensive interest in healthcare monitoring, artificial intelligence, and national security. In this context, we report the synthetic procedure of a three-dimensional (3D) metal-organic framework (MOF) comprising cadmium (Cd) metals as nodes and isoniazid (INH) moieties as organic linkers (CdI2-INH═CMe2) for designing self-polarized ferroelectret-based highly mechano-sensitive skin sensors. The as-synthesized MOF preferentially nucleates the stable piezoelectric β-phase in poly(vinylidene fluoride) (PVDF) and also gives rise to a porous ferroelectret composite film. Benefiting from the porous structure of 3D MOFs, composite ferroelectret film-based ultrasensitive pressure sensor (mechano-sensitivity of 8.52 V/kPa within 1 kPa pressure range) as well as high-throughput ( power density of 32 μW/cm2) mechanical energy harvester (MEH) has been designed. Simulation-based finite element method (FEM) analysis indicates that the geometrical stress confinement effect within the interpore region of the ferroelectret structure synergistically influences the mechano-electrical property of the MEH. In addition, 143 pC/N (∼4.5 times higher than commercial piezoelectric PVDF films) piezoelectric charge coefficient (d33) magnitude and superior response time (tr ∼ 8 ms) of this composite ferroelectret film enable the detection of different physiological signals such as coughing, pronunciation, and gulping behavior, making it a promising candidate for early intervention of healthcare, which may play a significant role in accurate alert of influenza and chronic obstructive pulmonary disease (COPD)-related symptoms. In addition, MEH enables the tracking of the subtle pressure change in the wrist pulse, indicating its usefulness in effective mechano-sensitivity. Since the cardiovascular signal is one of the vital parameters that can determine the on-going physiological conditions, the wireless transmission of the detected wrist pulse signal has been demonstrated. All of these features coupled with wireless data transmission indicate the promising application of MOF-assisted composite ferroelectret films in noninvasive real-time remote healthcare monitoring.

Impinging Performance of High-Pressure Water Jets Emitting from Different Nozzle Orifice Shapes

The impinging pressure of a water jet is a key factor in engineering applications, and the jet shape has a great influence on this pressure. In this paper, five different nozzle shapes were designed, and impacting tests were conducted based on a self-designed experimental platform using a PVDF piezoelectric film sensor and a high-speed camera to record the impacting data. Additionally, the computational fluid dynamics (CFD) method was also applied to study the velocity distribution. The results show that the pressure profiles of different water jet shapes impacting onto a solid surface present a consistent pattern, namely, an initial transient and enormous peak pressure and then a longer and smaller stagnation pressure. Although the stagnation pressure in this paper is not sufficiently obvious, the peak pressures of the five water jet shapes are much different from one another. Under the same inlet pressure, the peak pressure of the circular water jet is the largest, and those of the square, triangular, cross-shaped, and elliptical water jets decrease in turn. The flowing regimes captured by the high-speed camera together with the CFD simulation results indicate that the discrepancy in the peak pressure may be a combined action of the liquid velocities and jet head shapes.

Self-sensing piezoelectric bistable laminates for morphing structures

Bistable laminates offer opportunities for shape morphing, energy harvesting, and flow control devices. Smart materials such as piezoelectric macrofiber composites and shape memory alloys have been embedded in bistable laminates to actuate or harvest energy. However, sensor systems capable of measuring bistable shapes and snap-through events are lacking. In this paper, we present curved bistable laminates layered with piezoelectric PVDF films that can sense smooth shape changes as well as abrupt snap-through transitions. Near-static measurement is facilitated by a drift compensated charge amplifier with a large time constant that converts the sensor’s charge output into a measurable voltage with minimal drift error. The sensing function is demonstrated on mechanically-prestressed bistable laminates. The laminated composites include two sensor layers such that one measures the changes in curvature and the other measures snap-through events. An analytical model is presented in which strains and curvatures calculated using a laminated-plate model are fed into a linear piezoelectric model to calculate voltage. Shapes measured by the sensors correlate well with shapes measured using a 3D motion capture system. A model-based analysis is performed to understand the laminates’ design space.

Wearable multimode sensors with amplified piezoelectricity due to the multi local strain using 3D textile structure for detecting human body signals

Abstract In this study, a new wearable multi-local strain sensor (MLS-sensor) based on 3D textile structure with pre-strained monofilament was proposed, which features two modes. First, the vibration mode detects bio-signals from voice printing, respiration and blood pulse. Second, the tensile and compression mode, which detects signals from body movement based on pressure of fingertip and gait, four movement of neck, and joint movement (elbow and knee). Previous research studies mainly focused on investigation on how to enhance the output performance of piezoelectric PVDF film via nanostructure. However, this study explores how macro-sized 3D textile structure can improve the piezoelectric performance of PVDF film. Whereas, 3D textile structure has been commonly utilized as a pressure absorber due to the space caused by the monofilament that exhibits viscoelastic behavior. The MLS-sensor utilizes the pre-strained monofilament of 3D textile structure as a pressure transmitter to create amplified strain resulting from multi-local strain (MLS) in PVDF film in order to improve the PVDF piezoelectric performance. The MLS-sensor was shown to amplify the piezoelectric output voltage (4.6 V) up to 5 times (25.6 V) using the same pressure.

Design and experimental study of acceleration sensor based on PVDF piezoelectric film

PVDF piezoelectric film is a piezoelectric polymer material with excellent properties. In this paper, the research status of PVDF piezoelectric thin film was summarized, and the working principle of PVDF piezoelectric thin film accelerometer was introduced. On the basis of optimizing parameters, a cantilever PVDF piezoelectric film accelerometer and signal processing circuit were designed. The signal processing circuit which was composed of amplifier circuit and filter circuit was analyzed experimentally,and the frequency characteristic diagram of the filter circuit was obtained.The amplitude-frequency and phase-frequency characteristics of the filter circuit were better in a certain range,which can meet the design requirements.Experiments on the designed PVDF piezoelectric film accelerometer were carried out, including the calibration experiment of the PVDF accelerometer and the performance test of the sensor.The analysis results showed that the sensor has high sensitivity and good linearity, and can meet the measurement requirements.

Direct writing of PVDF piezoelectric film based on near electric field added by [Emim]BF4

PVDF/IL piezoelectric film based on [Emim]BF4-added was prepared by near electric field direct writing. The β-phase content and its electric property of the film were analyzed. The results showed that the content of β crystal phase of PVDF film was improved by the synergistic effect of IL ([Emim]BF4) and near electric field. When the amount of [Emim]BF4 added was 1.5 wt%, the relative β-phase content of PVDF film reached 85.09%, and the crystallinity is 47.84%. Increase in [Emim]BF4 content resulted in a significant increase in the relative dielectric constant of the film, from 6 to 285, but also accompanied by a sharp increase in dielectric loss. The d33 value of the film can be as high as −10 pC/N, and the output voltage from the cantilever beam vibration feedback indicates that the voltage strength of the [Emim]BF4-added film is greatly improved compared with the pure PVDF film.

Near static strain measurement with piezoelectric films

A fundamental challenge that prevents the implementation of piezoelectric sensors for measuring extremely low frequency (<1 mHz) events, such as aerodynamic pressure measurements, earthquake detection, and physiological monitoring, is their inability to measure static or very low frequency signals. To enable near static measurements, we present a low-noise, differential charge amplifier topology that performs real-time cancellation of drift in the output voltage while simultaneously increasing the gain of a conventional charge amplifier. A sensing frequency range from 0.01 mHz to 310 kHz with a voltage drift reduction of up to 95% is demonstrated. A theoretical sensitivity increase of up to 30 dB is achieved with the proposed topology compared to a basic charge amplifier with the same component tolerances, time constant, and allowable drift rate. The proposed circuit is interfaced with a piezoelectric PVDF film for evaluation of performance in the time and frequency domains. The measured voltage from uniaxial near DC strain measurements stays within 3% over a measurement period of 500 s. The paper further describes a linear piezoelectric strain sensor model and the various factors that influences the charge output, loading effect, and lateral cross-sensitivity of the sensor. The calculated strain–voltage relationship or the gage sensitivity agrees well with the measurements with a linearity error of less than 5% up to 1 millistrain.

Event Driven Time-logging System based on Continuous Operation of Real Time Clock towards Perpetual Electronics

This paper presents a novel time logging system using a real time clock (RTC) powered by a vibrational energy harvester to record the time of events when piezoelectric PVDF film as an event-driven sensor is activated. The power-management circuit normally remains in the sleep mode to cut power supply to the micro-processor and the ferroelectric random access memory. On the other hand, the RTC alone is powered by a battery to keep the time by seamless operation, which lowers the standby power consumption as small as 231 nW. As the PVDF film generates power, the developed power management circuit can supply load current upwards of 8 mA at 3.3 Vdc for external circuit to record the time of events with the energy consumption of 467 µJ.

Energy Harvesting Piezoelectric Wind Speed Sensor

In this paper, we demonstrate a miniature wind speed sensor consisting of a triangle-shaped bluff body attached to the free end of a cantilever incorporating a commercial PVDF piezoelectric film. In the wind, the bluff body causes regular vibration of the cantilever based on galloping, and the piezoelectric film converts the vibration energy into electrical energy. The vibration frequency of this device has an approximately linear dependence on wind speed, and so can be used to detect wind speed directly with high accuracy. In wind tunnel tests, a wind speed sensor based on this principle could detect the wind speed from 4.45 to 10 m/s, and measured speed was typically within 2% of the value obtained using a Pitot tube.

Fragment Velocity Test System Based on PVDF

In order to solve the problem of low measurement accuracy, large environmental interference and high cost of production in fragment velocity test, this paper proposed the fragment velocity test system by using PVDF piezoelectric film, NI-PXI platform and LabVIEW graphical programming language. The test system mainly includes PVDF film, adjusting circuit, acquisition module and terminal control software. The adjusting circuit amplifies the weak signal of the PVDF sensor. The acquisition module is responsible for reading the data collected by the data acquisition card for subsequent analysis and storage. The terminal control software executes data multi-channel acquisition, storage and display. The test system is stable and reliable with high accuracy through experimental verification.

Dynamic characteristics and optimization research on PVDF piezoelectric film force sensor for steel ball cold heading machine

According to cold heading process with overloaded craft, high-impact dynamic real-time measurement requirements, this paper presents researches on dynamic characteristics and optimization of PVDF piezoelectric film force sensor for steel ball cold heading forming quality monitoring, through the combination method of mechanism analysis, mathematical modeling, numerical simulation and experimental validation. The motivation and strategic objectives are to breakthrough dynamic time-varying impacting load measuring fundamental technologies in steel ball forging process. The structure of piezoelectric film force sensor is proposed. The theoretical calculation formula of natural frequency is deduced and calculated by using MATLAB software. The mechanical performance analysis on dynamic model and structural optimization simulation by FEM is carried out. In order to study the validity of the proposed method, a prototype of the sensor is fabricated. The static and dynamic calibration devices are designed to realize calibration experiments on the fabricated PVDF piezoelectric film force sensor. The differences among experimental value, simulation value and the theoretical value are given. The nonlinear error of the fabricated sensor is 0.197%. The sensor’s first order natural frequency value is 5238 Hz. It is proved that the PVDF piezoelectric film force sensor has superior dynamic performance and high accuracy for measuring deformation in steel ball. The paper will provide important scientific basis and technical foundation to achieve superior performance steel ball.

An Autonomous Power Management System with Event-driven Energy Harvester Switch

This paper presents a new use of piezoelectric PVDF film as an event-driven sensor switch that activates the power-management circuit for a subsequent wireless sensor ZigBee such that it would not consume extra power during the sleep mode. The circuit is designed to pick up a mechanical vibration with the PVDF film and control the self-holding circuit to keep flowing the drive current to the load until a reset pulse signal is received. The developed power management circuit can supply load current upwards of 33 mA at 3.3 Vdc for load resistance ranging between 100 Ω and 1 MΩ.

Kinematics and Mechanics analysis of trap-jaw ant Odontomachus monticola

Trap-jaw ants of the genus Odontomachus exhibit spectacularly rapid predatory and fugitive strikes. In order to reveal the extraordinary impact resistance of the apical teeth material, we analyzed the kinematics and mechanics of the closing mandibles. Odontomachus monticola is an Odontomachus species and extensive in China. We video-recorded jaw-strikes to measure the closing velocity and acceleration. The experimental results showed that O. monticola’s mandibles closed at a highest velocity of 35.42 m/s and a highest acceleration of 750,000 m/s2 within an average duration of 0.16 ms. In addition, in order to measure the strike force, we developed an extraordinary measuring method with poly (vinylidene fluoride) (PVDF) piezoelectric film. First, the dynamic calibration of the PVDF piezoelectric film was conducted, then the calibrated piezoelectric film was struck by O. monticola. Finally, the mandible strike force was calculated according to the calibration result and the output signal. The measurements results demonstrated that the strike force ranges from 102.2 N to 235.2 N, which is impressive contrast with O. monticola’s body weight.

Film formation and characterisation of PVDF piezoelectric polymer thin film by spray coating and its application to helical spring

Poly(vinylidene difluoride) (PVDF) thin film was formed by spray coating method. This method is suitable for fabricating a uniform thin film on a three-dimensional (3D) surface, even if it is complicatedly curved. PVDF is compatible with spray coating because it can be dissolved in an organic solvent. In previous study, we formed PVDF film by bar-coating method, which can deposit PVDF onto substrate by expanding it using a roller bar. However, this method limits coating targets to only flat substrates. In this study, spray coating was carried out to form PVDF film on a 3D surface. After coating, mechanical and piezoelectric properties of PVDF film were characterised. As a result, good mechanical and piezoelectric properties were confirmed. Power-generating element was fabricated using PVDF thin film spray-coated on a 3D helical spring and output voltage was obtained by compressing it.

Evaluation of output voltage characteristics by impact test of piezoelectric PVDF film

Evaluation of output voltage characteristics by impact test of piezoelectric PVDF film

Analysis of Voltage Generating Characteristics of Composite Rail Pad Composed of Piezoelectric PVDF Film and Polyurethane Bonding Materials

Analysis of Voltage Generating Characteristics of Composite Rail Pad Composed of Piezoelectric PVDF Film and Polyurethane Bonding Materials