Polyvinylidene Fluoride Film Research Articles

High Anti‐Jamming Flexible Capacitive Pressure Sensors Based on Core–Shell Structured AgNWs@TiO2

AbstractFlexible capacitive pressure sensors play an important role in electronic skin and human–machine interaction due to their high sensitivity and convenient preparation, comparing with those resistive/piezoresistive sensors. However, due to the complexity of the application environment, reported capacitive sensors often experience signal instability by electromagnetic interference and proximity effects. The great challenge for capacitive sensors is to maintain sensitivity and wide linear range while reducing interference. This study proposes a high anti‐jamming capacitive flexible pressure sensor with polyvinylidene fluoride (PVDF)@AgNWs@TiO2 film as the dielectric layer. Core–shell structure‐based AgNWs@TiO2 is embedded into the PVDF film. The introduction of the core–shell structure not only enhances the initial capacitance but also balances the dielectric constant, dielectric loss, and breakdown strength of the dielectric layer. The sensor is validated to exhibit a high signal‐to‐noise ratio for a variety of interference sources and is demonstrated with an intelligent glove sensing system, which provides a new idea for developing a high anti‐jamming capacitive flexible pressure sensor.

Structure and pyroelectric properties of PVDF ferroelectric films obtained by 3D printing

This article reports a method to produce polymer films of polyvinylidene fluoride (PVDF) by an additive manufacturing (3D printing). Method Fused Deposition Modeling (FDM) allows using PVDF and its copolymers not only in microelectronics as pyroelectric and piezoelectric sensors, as well as creating dynamic memory elements, organic solar cells and used in robotics. The surface morphology of the samples observed by scanning electron microscopy (SEM) presents in this paper. Pyroelectric measurements performed by the dynamic method show the presence of a noticeable pyroelectric response in PVDF films obtained using additive technologies, bypassing the orientation extraction stage. The calculation of the pyroelectric coefficient gives values corresponding to the values of the pyroelectric coefficient for PVDF samples obtained by traditional methods.

Osteogenic activity of bone: Novel approach of polyvinylidene fluoride films, marrow blood supply, and ultrasound stimulation

AbstractElectric fields used in bone stimulation are based on the application of direct current, but some drawbacks exist, such as the need for an external power source. Piezoelectric poly(vinylidene fluoride) (PVDF) has attracted interest for biomedical applications due to its flexibility, low toxicity, and the piezoelectric response to mechanical stimuli. This study aimed to investigate the effects of PVDF films on bone regeneration in rabbit tibias to assess the potential improvement in osteogenesis. An initial exploratory experiment was performed to determine optimal parameters for regulating the marrow blood supply. The second experiment focused on examining the effects of ultrasound stimulation on the implant's osteogenic capacity. The results showed that PVDF films have a notable impact on the extraskeletal bone formation and bone density in a secluded microenvironment with and without microperforations. At 60 days after surgery, tibias with marrow blood supply reached higher bone volumes and density and they were consistent with the cellular activity. Our results suggest that piezoelectric PVDF films have osteogenic characteristics and can be used to enhance new bone formation in a secluded space, thus reinforcing their biocompatibility nature. Additional studies are required to analyze the benefits of ultrasound stimulation.

Halide Tunablility Leads to Enhanced Biomechanical Energy Harvesting in Lead-Free Cs2SnX6-PVDF Composites.

The main challenges impeding the widespread use of organic-inorganic lead halide perovskites in modern-day technological devices are their long-term instability and lead contamination. Among other environmentally convivial and sustainable alternatives, Cs2SnX6 (X = Cl, Br, and I) compounds have shown promise as ambient-stable, lead-free materials for energy harvesting, and optoelectronic applications. Additionally, they have demonstrated tremendous potential for the fabrication of self-powered nanogenerators in conjunction with piezoelectric polymers like polyvinylidene-fluoride (PVDF). We report on the fabrication of composites constituting solvothermally synthesized Cs2SnX6 nanostructures and PVDF. The electroactive phases in PVDF were boosted by the incorporation of Cs2SnX6, leading to enhanced piezoelectricity in the composites. First-principles density functional theory (DFT) studies were carried out to understand the interfacial interaction between the Cs2SnX6 and PVDF, which unravels the mechanism of physisorption between the perovskite and PVDF, leading to enhanced piezoresponse. The halide ions in the inorganic Cs2SnX6 perovskites were varied systematically, and the piezoelectric behaviors of the respective piezoelectric nanogenerators (PENGs) were investigated. Further, the dielectric properties of these halide perovskite-based hybrids are quantified, and their piezoresponse amplitude, piezoelectric output signals, and charging capacity are also evaluated. Out of the several films fabricated, the optimized Cs2SnI6_PVDF film shows a piezoelectric coefficient (d33) value of ∼200 pm V-1 and a remanent polarization of ∼0.74 μC cm-2 estimated from piezoresponse force microscopy and polarization hysteresis loop measurement, respectively. The optimized Cs2SnI6_PVDF-based device produced an instantaneous output voltage of ∼167 V, a current of ∼5.0 μA, and a power of ∼835 μW across a 5 MΩ resistor when subjected to periodic vertical compression. The output voltage of this device is used to charge a capacitor with a 10 μF capacitance up to 2.2 V, which is then used to power some commercial LEDs. In addition to being used as a pressure sensor, the device is employed to monitor human physiological activities. The device demonstrates excellent operational durability over a span of several months in an ambient environment vouching for its exceptional potential in application to mechanical energy harvesting and pressure sensing applications.

Effective interactions and dielectric study of polymer nanocomposite thin films of polyvinylidene fluoride and graphene oxide

ABSTRACT Polyvinylidene fluoride (PVDF) is a well-known fluoropolymer for its electronic applications. The present work investigates the influence of Graphene oxide (GO) in various weight percentages over the dielectric profile of the PVDF matrix. Field emission scanning electron microscopy (FESEM) is used to explain the morphological features of the samples. The thermal stability of the PVDF polymer with the addition of GO was studied using thermogravimetric analysis (TGA). X-ray diffraction spectroscopy (XRD), confocal Raman microscopy (CRM), and Fourier Transform infrared spectroscopy (FTIR) were used to interpret the appreciable interfacial interactions between the matrix and the nanofiller and possible phase transformations. The presence of polar and non-polar polymorphic phases in PVDF was verified with the help of XRD, FTIR, and CRM analyses. The band gap energy of the samples was determined using the Tauc-plot method from UV–visible observations. The variation in the polarity of the matrix with the inclusion of GO is also noted. The dielectric and AC conductivity measurements were done at 100 Hz and 2 MHz. All these ascertain the candidacy of PVDF/GO nanocomposite thin films to be incorporated into electronic devices of this era.

Monitoring of human dynamics by a flexible and comfortable polyvinylidene fluoride (PVDF) sensor

With the increasing demand for self-adaptive electronics, stretchable and conformable sensors with high sensitivity, stretchability, and self-adhesive are significant intelligent devices. Here a novel tactile sensor is demonstrated that maintains conformal contact to the object for efficient movement monitoring. The device, which was composed of the “H” well-manicured thermoplastic elastomer (TPE), a rectangular polyvinylidene fluoride (PVDF) film coupled with a silver electrode and clamped into the copper-clad signal line ends, and a “U” shaped super-elastic silica gel layer, provided satisfactory performance. The device was investigated as a dynamic monitoring sensor due to its stretchable and conformal configuration. The mechanical stability and high sensitivity suggested that, when attached to the skin of participants, the sensor detected motion induced strain which was experimentally demonstrated. The results show that the novel biomimetic sensor is effective in monitoring human dynamics, with an accuracy exceeding than 98.3%. The stretchable and conformable sensor is low-cost and nontoxic with potential applications in clinical, conformal detection, and artificial intelligence.

Ultraflexible polyvinylidene fluoride film based amperometric enzyme-free sensor for selective detection of uric acid in a trace level.

The present invention describes a novel flexible nanosensor for the electrochemical detection of uric acid (UA) present in urine. The synthesized graphite-boron nanocomposite with an average thickness of ∼32 nm was grown up on a flexible polyvinylidene fluoride film with an average thickness of ∼50 μm and it acts as a nonenzymatic sensor for UA. The developed flexible sensor showed a prominent reduction peak in cyclic voltammetry and amperometric response with the presence of different concentrations of aqueous UA solution. In the electrochemical study, the redox peak was generated near ∼-0.42 V with a detection limit of around ∼2.09 μM as the bottom level. The high robustness of the developed sensor originated from the polymeric film base and the rapid response time of ∼0.5 s for detecting UA present in human urine. The interference property of the sensor was confirmed in the presence of bilirubin and creatinine as an eventual reference toward selectivity. The phase and morphology of the sensor surface were extensively observed before and after sensing to comprehend the electrochemical interaction between the sensor and target molecules. The generated quantitative results of the integrated system were verified by testing known and unknown concentrations of UA solutions.

A flexible triboelectric nanogenerator based on poly(vinylidene fluoride-vinyl chloride) for basketball dribbling technique training

Recently, intelligent sports monitor devices based on self-powered sensor technology have received widespread attention. Here, we designed a triboelectric nanogenerator based on a poly(vinylidene fluoride-vinyl chloride) PV(DF-A) film and a polydimethylsiloxane (PDMS) film (PP-TENG) to harvest bio-mechanical energy and serve as the basketball training sensor. After experimental testing, the electron loss ability of the PV(DF-A) film is greater than that of a polyvinylidene fluoride film. Also, the open-circuit voltage (Voc) and short-circuit current density (Jsc) of PP-TENG can get to 1856.4 V and 269 mA m−2, respectively. The PP-TENG can obtain a maximum power density of 130.28 W m−2. Moreover, the PP-TENG sensor can monitor various gait patterns of players in basketball and achieve auxiliary analysis of basketball training strategies. This research will promote the development of intelligent basketball training sensors.

Large-scale fabrication and performance improvement of polyvinylidene fluoride piezoelectric composite films

Sensing applications such as wearable electronics, electronic skin, and soft robotics using flexible piezoelectric films have received extensive attention. In this study, we fabricate large-scale 0–3 type composite films of polyvinylidene fluoride (PVDF)-doped modified lead zirconate titanate (PZT) particles (PZT@UP) through an extrusion-casting process to enhance piezoelectric properties and explain the piezoelectric performance mechanism. The introduction of PZT@UP particles improved the dielectric permittivity of the composite films and promoted the polarization of PVDF, which positively affected the piezoelectric properties of PVDF/PZT@UP films. The composite film with 25 wt% PZT@UP possessed an excellent piezoelectric coefficient (d33) of 29 pC/N, which was 93% higher than that of neat PVDF (15 pC/N). Moreover, the addition of PZT@UP particles effectively inhibited the movement of PVDF molecular chains and improved the mechanical modulus stability of the composite films. The law of electrostrictive effect of the PVDF/PZT@UP composite films is clarified from the aspects of the movement of PVDF molecular chains, the principle of electric field distribution, and the construction of the internal electric field. Further, the similarities and differences between the piezoelectric and electrostrictive mechanisms of the PVDF/PZT@UP composite films are summarized. The extrusion-casting process combined with modified fillers shows promising potential in improving wear and tear of and electricity generation from PVDF-based composite films, leading to a profound impact on the development of large-scale fabrication of piezoelectric sensors.

Thermal Conductivity of Polyvinylidene Fluoride Films with a Multi-Scale Framework.

The orientation of amorphous regions in pure polymers has been noted to be critical to the enhancement of thermal conductivity (TC), but the available reports are still rather few. Here, we propose to prepare a polyvinylidene fluoride (PVDF) film with a multi-scale framework by introducing anisotropic amorphous nanophases in the form of cross-planar alignments among the in-planar oriented extended-chain crystals (ECCs) lamellae, which show an enhanced TC of 1.99 Wm-1 K-1 in the through-plane direction (K⟂) and 4.35 Wm-1 K-1 in the in-plane direction (K∥). Structural characterization determination using scanning electron microscopy and high-resolution synchrotron X-ray scattering showed that shrinking the dimension of the amorphous nanophases can effectively reduce entanglement and lead to alignments formation. Moreover, the thermal anisotropy of the amorphous region is quantitatively discussed with the aid of the two-phase model. Superior thermal dissipation performances are intuitively displayed by means of finite element numerical analysis and heat exchanger applications. Moreover, such unique multi-scale architecture also results in significant benefit in the improvement of dimensional stability and thermal stability. This paper provides a reasonable solution for fabricating inexpensive thermal conducting polymer films from the perspective of practical applications.

Acoustic and electromagnetic properties of a martensitic-aging ferro-nickel alloy with the addition of copper under mechanical tension

The paper presents the results of a study of the effect of mechanical longitudinal uniaxial stretching on the velocity of longitudinal and transverse waves in XM-12 steel samples. During the research, an acoustic mirror-shadow method was used on multiple reflections of the control using an electromagnetic acoustic transducer and a piezoelectric transducer based on a polyvinylidene fluoride film to excite and receive waves. The elastic modules of the studied samples and the coefficients of acoustoelasticity are calculated.

Effects of Fabrication Conditions on the Partial Discharge Mitigation Performance of Electrets for Power Electronic Driven Systems

In our previous studies, we have shown that electrets can be designed to mitigate partial discharge (PD) in power electronic converter (PEC)-driven systems by neutralizing locally-enhanced harmful electric fields. Surface charge density is one of the main factors that determines the PD mitigation performance of electrets. In this study, we fabricate electrets from polyvinylidene fluoride (PVDF) films under various charging conditions including voltage magnitude, charging duration, voltage polarity, and temperature using triode-corona discharge method. The surface charge density and PD mitigation performance of the fabricated electret films are assessed by surface potential measurements and PD experiments. <styled-content style="color:black">The effects of fabrication temperature on electret surface charge stability, and the impacts of atmospheric conditions on electret surface charge density and PD magnitude are discussed.</styled-content> This study provides knowledge that is essential for establishing the fabrication conditions of electrets that can effectively mitigate PD in PEC-driven systems.

Embedded Pt-PVDF sensor without compromising mechanical properties of GFRP for on-line sensing

A wide variety of embedded sensors are currently used for structural health monitoring of glass fiber reinforced polymer (GFRP) composites. However, some studies showed the sensor embedding scarified the mechanical performance; several studies showed less influence on static performance but not embedded in the maximum stress area. In this work, we designed an embedded sensor without scarifying static and fatigue mechanical performances of the composites based on the flexible piezoelectric film-polyvinylidene fluoride (PVDF). Moreover, the sensor in-situ monitored the damage and fatigue evolution successfully until the specimens failed. The PVDF sensor in this work provides a reliable alternative for GFRP in structural health monitoring.

Radial mesoporous silica supported Eu3+‐functionalized carbon dots for ratiometric tetracycline detection and their polyvinylidene fluoride hybrid film for temperature sensing

A radial mesoporous silica (mSiO2) supported Eu3+‐functionalized carbon dots (CDs) nanocomposite (mSiO2‐CDs‐Eu) was successfully prepared using citric acid as CD precursors, showing specific ratiometric tetracycline (TC) fluorescence sensing behavior. The blue fluorescence of CDs is quenched by the internal filtering effect with TC, and the red fluorescence intensity of Eu3+ ions is improved on account of an antenna effect. The self‐calibrated ratiometric fluorescence sensing of TC by mSiO2‐CDs‐Eu showed a minimum detection limit of 30 nM. In addition, a mSiO2‐CDs‐Eu hybridized polyvinylidene fluoride (PVDF) film was developed for optical temperature sensing with a high‐temperature sensitivity of 1.69% °C−1 in the physiological temperature range of 25–45°C and a temperature resolution greater than 0.04°C. This work demonstrates a feasible way in fabricating dual‐functional mSiO2‐CDs‐Eu nanocomposite with optical ratiometric sensing properties toward both TC and temperature changes, opening its promising applicability for food security and temperature monitoring.

Wide-band electrical and electromechanical properties of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) piezoelectric films using electro-acoustic reflectometry

Thin piezoelectric polymer films are used in increasingly more high frequency applications. However, they are not well characterized up to the gigahertz range. In this paper, polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) films are mechanically and electrically characterized using the electro-acoustic reflectometry (EAR) method from 20 MHz to 2 GHz. In addition to mechanical and electrical properties, nonuniform poling is detected in the tested PVDF-TrFE samples showing a larger piezoelectric constant in the middle of the film and thus generating even and odd resonance modes.

A Ratiometric Fluorescent Sensor Based on Silicon Quantum Dots and Silver Nanoclusters for Beef Freshness Monitoring

A ratiometric fluorescent sensor with hydrogen sulfide (H2S) and methanthiol (CH3SH) sensitivity was developed to real-time monitor beef freshness. A silicon quantum dots (SiQD) and silver nanoclusters (AgNC) complex, namely SiQD-AgNC, was used as the dual emission fluorescence materials. Due to the fluorescence resonance energy transfer (FRET) effect between SiQD and AgNC, when the fluorescence of AgNC (610 nm) was quenched by H2S or CH3SH, the fluorescence of SiQD (468 nm) recovered, resulting in an increase of the fluorescent intensity ratio (I468/I610). I468/I610 showed a linear relationship with the H2S concentration within the concentration range of 1.125-17 μM, with a limit of detection (LOD) value of 53.6 nM. Meanwhile, I468/I610 presented two linear relationships with the CH3SH concentration within the concentration range of 1.125-17 μM and 23.375-38.25 μM, respectively, with a LOD value of 56.5 nM. The SiQD-AgNC complex was coated on a polyvinylidene fluoride (PVDF) film to form a portable SiQD-AgNC/PVDF film sensor. This film showed purplish red-to-cyan color changes in response to H2S and CH3SH, with LOD values of 224 nM and 233 nM to H2S and CH3SH, respectively. When the film was used to monitor beef freshness at 4 °C, its fluorescent color gradually changed from purplish red to cyan. Hence, this study presented a new ratiometric fluorescent sensor for intelligent food packaging.

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.

The Use of a PVDF Array to Measure the Stress Field Inside an Elastic Material.

This paper reports a series of experimental and modeling investigations on two piezoelectric arrays made of polyvinylidene fluoride (PVDF) films. They were embedded inside rubber cylinders and used to directly measure the internal stresses generated by various external excitations applied to the top surface of the cylinder. Corresponding finite element (FE) models were established to reveal the relationship between the PVDF output and the stress field applied to it. This research improves the understanding of the output mechanism of the embedded PVDF and provides useful information for the design of PVDF sensors.

Stretchable Strain and Strain Rate Sensor Using Kirigami‐Cut PVDF Film

AbstractWearable sensor technology has recently received considerable interest because of the emergence of digital healthcare and its expanding markets. Wearable sensors require stretchability, biocompatibility, and high performance. In this study, stretchable strain sensors are designed and fabricated using a kirigami‐cut polyvinylidene fluoride (PVDF) film. Further, the biocompatibility of PVDF is examined. Kirigami cutting can improve stretchability by 400% using the structural distortion of the cut parts. Compared to previously reported sensors, the developed sensor can measure the strain and strain rate simultaneously. The effect of strain and strain rate on the piezoelectric performance is analyzed. The output voltage increases exponentially with the strain, and a high strain rate results in high piezoelectric efficiency. The strain and strain rate can be detected by analyzing the sensor property, which illustrates the relationship between the voltage and voltage change rate. The sensing performance is evaluated using various kirigami patterns. Theoretical analysis reveals the dependence of output voltage on strain and strain rate. Finally, the developed sensor is successfully used as a wearable sensor for athlete rehabilitation and posture monitoring.

Three-dimensional force detection using PVDF and room temperature-vulcanized silicone rubber layers

Three-dimensional force perception plays an extremely important role in human-computer interaction. The main objective of the present study is to propose a three-dimensional force detection sensor using room temperature-vulcanized silicone rubber, polyvinylidene fluoride (PVDF), and a silver coating layer. The sensor was designed in a cylindrical structure to detect the tangential force. The performed analyses reveal that the silver coating layer improves the surface charge output of the PVDF film. The output peak voltage of the sensing unit is 271.7% higher than that of the single PVDF film. The sensor has a response time of 40 ms. It is found that the angle detection error of the sensor along horizontal and vertical directions is less than 2.79° and 0.88°, respectively. In order to evaluate the performance of the proposed sensor, it is fixed on the mechanical hand to perform grasping and sliding tests. The tested results show that the proposed sensor can effectively identify the weight and slip of the object, and can be used in the field of manipulator clamping control.