Polyvinylidene Fluoride Thin Films Research Articles

Spin-transport across semi-crystalline polyvinylidene fluoride thin films in Ta/Co/PVDF/NiFe pseudo spin-valve devices

Room temperature magnetoresistance (MR) across semi-crystalline polyvinylidene fluoride (PVDF) thin films in Ta(2 nm)/Co(15 nm)/PVDF/NiFe(28 nm) pseudo-spin-valve devices (PSVs) are systematically investigated by varying PVDF thicknesses from 80 − 230 nm and applied bias voltages up to 100 mV. NiFe, Ta/Co magnetic bottom and top electrodes, and PVDF thin films are deposited by DC magnetron sputtering and spin-coating methods. The structural, microstructural, and magnetic natures have been evaluated using grazing incidence X-ray diffraction, atomic force microscopy, and magneto optic kerr effect systems. Electrical characteristics reveal a maximum MR of ∼0.25 % at 60 mV bias voltage across PVDF-80 nm and ∼0.08 % across PVDF-230 nm & PVDF- 120 nm devices. A constant MR is found across all the devices up to 100 mV applied bias voltages. In addition to the electrical spin injection evaluation, coplanar waveguide ferromagnetic resonance measurements are utilized to validate the spin injection into PVDF layers by estimating the Gilbert damping parameters of NiFe and PVDF/NiFe bilayers. Furthermore, low MR in PSVs is discussed with the parallel spin-dependent conducting channels corresponding to PVDF’s amorphous, alpha, and beta crystalline phases.

Enhanced microwave absorption and mechanical performance of polyvinylidene fluoride thin films embedded with novel activated carbon and manganese ferrite

AbstractThin composite films hold great promise for microwave devices for microwave absorption. This work mainly focuses on the investigation of the microwave absorption and mechanical studies of a composite thin film of activated carbon and manganese ferrite as conductive fillers within a polyvinylidene fluoride (PVDF) matrix. The production of activated carbon was successfully accomplished using a pyrolysis technique. Composite films consisting of polyvinylidene fluoride (PVDF) and activated carbon‐manganese ferrite were fabricated using a solution blending method. The composite films maintained a consistent concentration of activated carbon at 5 wt%. The characterization of the materials was conducted using scanning electron microscopy and X‐ray diffraction. The composite consists of 3 wt% of MnFe2O4 and 5 wt% Activated carbon/PVDF showed exceptional absorption properties and achieved a minimum reflection loss of around −38 dB at a frequency of 8–12 GHz at a thickness of 2 mm. Significantly, the composite film exhibited a greater tensile strength than the PVDF film. The results of our study highlighted the enhanced microwave absorption and economical manufacturing technique for producing composite films. These films exhibit promising microwave‐absorbing properties in stealth applications.Highlights A facile strategy to fabricate thin film PVDF composites was proposed. Novel activated carbon was synthesized to enhance the conductivity. Achieved reflection loss of around −38 dB at a frequency of 8–12 GHz. Synergistic effects of fillers enhanced dielectric and magnetic losses. Exhibited efficient mechanical performance and microwave absorption.

Enhancement of energy storage in nanocomposite thin films: Investigating PVDF-ZnO and PVDF-TZO for improved dielectric and ferroelectric characteristics

In contrast to a polymer nanocomposite for high energy density application, a lead-free material such as zinc oxide (ZnO) and a non-toxic polymer matrix such as polyvinylidene fluoride (PVDF) can serve as a potential candidate for use in eco-friendly applications. In the present report, an effort has been made to enhance the dielectric behaviour of the PVDF-based nanocomposites by adding ZnO nanoparticles (NPs) and TiO2-coated ZnO NPs (TZO) as nanofillers. A wet chemical precipitation technique was adopted to synthesize the thin films of PVDF,PVDF-ZnO, and PVDF-TZO nanocomposites. The structural, dielectric, ferroelectric, and energy density studies of PVDF, PVDF-ZnO, and PVDF-TZO nanocomposites thin films were performed for different concentrations (10%, 20%, 30%, and 40%) of nanofillers. Structural characterization carried out using x-ray diffraction studies confirmed the formation of PVDF-ZnO and PVDF-TZO nanocomposite thin films as the diffraction peaks (110) and (200) belonging to β-phase of PVDF, and (100, (002), (101), (110), (103), (200), (112), and (210) peaks were observed for ZnO, and (200), (116), (202) peaks belonging to TiO2 in case of PVDF+ 10% TZO and PVDF+40% TZO thin films. The functional groups belonging to β-phase of PVDF and ZnO were detected using a Fourier transform infrared spectrometer (FTIR). The surface microstructural of pure PVDF thin films showed spherulites and microimages of PVDF+ 10% ZnO and PVDF+ 10% TZO thin films depicted the inhomogeneous distribution of particles in the PVDF matrix. The maximum value of the dielectric constant, the maximum value of energy density, maximum remnant polarization, and the minimum value of dielectric loss for PVDF-TZO. PVDF-TZO thin films show an energy density of 65.3 μJ/cm3 for 40% of the nanofiller (TZO).

Influence of 100 MeV 16O7+ ion irradiation on the structural, morphological, dielectric, and electromagnetic interference shielding properties of ferroelectric PVDF polymer

Polyvinylidene fluoride (PVDF), with β polymorph, is a versatile ferroelectric polymer in device fabrication. Its flexibility, lightweight, and ease of fabrication make it an alternative for electromagnetic interference shielding effectiveness (EMI-SE) improved through swift heavy ion (SHI) irradiation. For the first time, we modified PVDF thin films for EMI-SE applications, exposing them to a 100 MeV oxygen ion beam at varying fluencies. Our analysis encompassed investigating structural study, bonding interactions, surface morphology, and elemental analysis using X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), and Field Effect Scanning Electron Microscopy (FESEM) with Energy Dispersive X-ray Spectroscopy (EDS) respectively. Further, we measured dielectric response, cole-cole plot and EMI-SE in Ku-band (12–18 GHz) region using a vector network analyzer (VNA). The results revealed distinctive variations due to the deposition of 100 MeV oxygen ion beams, emphasizing the significant potential of irradiated PVDF thin films for EMI-SE applications. This study contributes to understanding the transformative impact of ion beam exposure on PVDF thin films and highlights their practical promise in emerging technological applications, particularly in EMI-SE.

Influence of Indium Tin Oxide (ITO) poling temperature in vacuum on surface roughness of Polyvinylidene Fluoride(PVDF) film

The surface roughness is a significant parameter of the performance of PVDF thin film sensors. In this work, we have investigated the effect of ITO poling in vacuum at various temperature on the surface roughness of uniaxially stretched PVDF film. The influence of poling temperature on the surface roughness of PVDF film was examined using atomic force microscopy (AFM). In this work, the AFM data are obtained through the database, and topography is analyzed using Gwydion Software (GS). GS has characterized surface roughness in terms of Average Roughness (Ra), Root Mean Square (Rrms), and Arithmetic average height (Rz). The results show that the GS can detect and measure profile thickness and roughness on a nanoscale with reliable accuracy. The results confirm that the increased poling temperature can reduce the roughness of the surface.

Enhancing wettability and adhesive properties of PVDF-based substrates through non-thermal helium plasma surface modification

Polyvinylidene fluoride (PVDF) has gained attention as a promising material for tissue engineering due to its biocompatibility and piezoelectricity. However, achieving proper cell adhesion to PVDF surfaces remains a challenge. This study focuses on the preparation and characterization of PVDF-based substrates, including PVDF thin films and nanocomposites incorporating CoFe2O4 magnetic nanoparticles. Helium plasma treatment is employed to modify the surface properties of these substrates. The plasma treatment induces significant changes in the topography of the PVDF-based nanocomposites. The roughness values of the samples increase from 2–3 nm to 14–17 nm after 90 s of plasma treatment, leading to enhanced hydrophilicity with an average contact angle below 60°. Importantly, the helium plasma treatment preserves the magnetic and structural properties of the substrates, suggesting the retention of their magnetoelectric properties and, thus treated composites hold potential for remote stem cell activation. We provide evidence of cytocompatibility and improved adhesive properties of plasma-treated substrates using human mesenchymal stem cell cultures.

A comparative analysis of flexible pvdf based smart films for advanced electromagnetic shielding applications using a machine learning approach

Due to emerging technology, the usage of electronic gadgets has paved a route for the arousal of Electromagnetic Interference (EMI) pollution. Electromagnetic pollution is considered a global threat that can harm all biological systems and technological equipment. To overcome this issue, a suitable shielding material has to be implemented to attenuate the incoming electromagnetic waves. On the other hand, compared to traditional materials, recently, polymers have grabbed excellent responses in various fields of material science and modern chemistry. Specifically, functional polymers are increasing their scope in industry and academia due to their unique features, such as magnetic, catalysis, optical and piezoelectric properties. In this regard, Polyvinylidene Fluoride (PVDF), a well-known semicrystalline polymer from the family of Fluoropolymers, has achieved remarkable in various applications of sensors, actuators, biomedical scaffolds and energy harvesting devices. PVDF has also contributed excellent outcomes as a shielding material as they are transparent to light and flexible. Hence, this research work attempts to fabricate PVDF thin films with various weight percentages of nanofillers such as Zinc oxide (ZnO), Zirconium oxide (ZrO2), and Titanium dioxide (TiO2). Further, all the samples were tested for electromagnetic shielding effectiveness (SE). Further, these experimental results were compared with statistical and computational approaches such as the Gradient Descent Algorithm (GDA) and Response Surface Methodology (RSM). Based on the experimental results, it was observed that the PVDF nanofilm fabricated with 0.3 wt% of ZrO2, 0.5 wt% of TiO2and 0.3 wt% of ZnO nanofillers had achieved a maximum EMI SE of 11.4 dB at X-band frequency of 8–12 GHz.

Characterization of dynamic confinement response of potting materials at different strain rates and temperatures

A Kolsky compression bar was modified with an instrumented confining tube for characterizing dynamic confinement response of materials at various strain rates. A thin film polyvinylidene fluoride (PVDF) force transducer was designed and integrated to the confining tube for direct in-situ measurement of confining pressure when the specimen is subjected to dynamic axial compressive load such that the mean stress-volumetric strain response of the specimen material is able to be determined. An environmental chamber was also implemented to the Kolsky compression bar for characterizing dynamic confinement response of materials at different environmental temperatures. After careful calibration of the instrumental confining tube, five different potting materials (EPON 828, EPON 828 filled with glass microballoons (GMBs), Sylgard 184, Sylgard 184 filled with GMBs, and expanded polystyrene (EPS) foam) were characterized with the modified Kolsky compression bar at different strain rates and environment temperatures. The effects of strain rate and temperature on the mean stress-volumetric strain response were determined for all five potting materials. Experimental uncertainties were also presented.

Research on the location of space debris impact spacecraft based on genetic neural network

The existence of space debris will pose a serious threat to the safety of spacecraft in orbit and cause serious impact damage to spacecraft. Therefore, the timely and accurate determination of the impact location of space debris is very important to improve the safety and reliability of the orbiting spacecraft in the long run. This paper proposes an intelligent back-propagation artificial neural network-based algorithm for locating the impact source of space debris. The method of building and training the algorithm is described, based on the moment of arrival of the stress waves detected by the PVDF (Polyvinylidene Fluoride) sensor array and the sensor coordinates. Based on the ABAQUS finite element simulation data, the neural network is trained. The result shows that compared with the traditional TOA (Time of Arrival) localization algorithm, the localization accuracy of the BP (Back Propagation) neural network localization algorithm is improved by 34.7%. The optimal objective is to minimize the error between the space debris impact point and the localization point. The parameters of the PVDF sensor array (diameter d of the circular PVDF thin film sensor, radius R of the PVDF sensor array) were optimized by genetic algorithm, and the optimal sensor array parameters were obtained based on the optimization algorithm.

Improving beta phase of spin coated PVDF thin films by doping with silver nanoparticles

This research deals with the effect of process parameters of spin coating such as spinning speed, weight composition of silver nanoparticles (AgNP), and annealing duration on the phase change of polyvinylidene fluoride (PVDF) thin films. FTIR spectroscopy along with XRD confirmed the transformation of α to β-phase in the PVDF thin films. The spin coated films exhibited higher β-fraction than that of the pristine PVDF. The β-fraction in the thin films was mainly influenced by the addition of AgNP. The DSC results showed decrease in crystallinity from 63.74 to 53.21% with increase in spinning speed from 1000 to 3000 rpm due to the over-stretching of crystalline lamellae.

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.

Effects of Porosity on Piezoelectric Characteristics of Polyvinylidene Fluoride Films for Biomedical Applications.

Objective: The objective of this work is to study the effects of porosity on mechanical and piezoelectric properties of polyvinylidene fluoride (PVDF) films for biomedical applications. Impact Statement: By investigating the piezoelectric properties of PVDF and the porosity effect on its electromechanical performance, there is potential for further development of PVDF as a hemodynamic sensor that can lead to further technological advancements in the biomedical field, benefiting patients and physicians alike. Introduction: PVDF thin films have shown potential in the application of hemodynamic flow sensing and monitoring the effects on blood flow caused by prosthetic valve implantation via the transcatheter aortic valve replacement operation. The piezoelectric performance of PVDF films can be influenced by the porosity of the material. Methods: In this study, strain tracking was performed on thin film PVDF specimens with various levels of porosity and pore sizes to determine the mechanical properties of the specimens. The mechanical properties were used to model the PVDF material in COMSOL multiphysics software, in which compression test simulations were performed to determine the piezoelectric coefficient d33 of the PVDF. Results: A decline in the elastic modulus was found to be highly inversely correlated with porosity of the specimens and the simulation results show that elastic modulus had a much greater effect on the piezoelectric properties than Poisson's ratio. Conclusion: A combination of experimental and computational techniques was able to characterize and correlate the mechanical properties of PVDF films of varying porosities to their piezoelectric properties.

Harvesting airflow energy from circular cylinder wake via a thin polyvinylidene fluoride film

To improve the characteristics of airflow energy harvesting, this paper presents a new piezoelectric wind energy harvester (PWEH), in which a polyvinylidene fluoride (PVDF) film was directly located in the wake of the circular cylinder. Four important parameters were independently varied for detailed experimental investigations: wind speed, spacing ratio for the distance between the center of the circular cylinder and the tip of the PVDF film to the circular cylinder diameter, diameter of the circular cylinder, and load resistance. The results indicated that the designed PWEH performed optimally with the occurrence of resonance, maintaining a relatively high output when significantly exceeding the resonance wind speed. The PVDF film inhibited the vortex shedding of the circular cylinder, which weakened with increasing spacing ratio. The optimum value of the spacing ratio should be approximately 2.5, which yields an effective coupling between the vortex and structure. The diameter of the circular cylinder played an important role in determining the output power. The match between the load resistance and PWEH also contributed to the high-level performance. Moreover, with an increase in the diameter of the circular cylinder, the increasing blockage ratio unexpectedly enhanced the vortex shedding frequency and decreased the theoretical resonance wind speed, which provided a new orientation for improving the performance of such PWEHs.

The Electromagnetic Interference Shielding Effectiveness and Dielectric Response of PVDF-nTiO2Nanocomposites Thin Films

This paper presents electromagnetic interference (EMI) shielding effectiveness (SE) and dielectric response of Polyvinylidene Fluoride (PVDF) and PVDF-Titanium dioxide (nTiO2) nanocomposite thin films. nTiO2 nanoparticles were synthesized by the combustion method using urea as fuel. PVDF and PVDF-nTiO2nanocomposite thin films of different wt% of TiO2as fillers in the PVDF matrix were prepared using the solvent evaporation method. The synthesized nanocomposite thin films were characterized by XRD, FTIR, and SEM. The EMI-SE was studied in the frequency range 0.5 - 8GHz and dielectric response in 10Hz - 8MHz at room temperature. The EMI-SE shows up and down valleys in S-Band with an average variation of ⁓28 and ⁓35 dB at 2 and 4GHz respectively and remains stable in C- Band agreeing with existing literature. The dielectric constant of PVDF-nTiO2 nanocomposite thin films decreases with an increase in frequency and anomaly for 10wt% of nTiO2 fillers in the PVDF matrix at standard frequency. HIGHLIGHTS TiO2 nanoparticles were synthesized by the combustion method using urea as fuel PVDF and PVDF-nTiO2 composites were prepared using the solvent evaporation technique The addition of nanoparticles to the PVDF polymer has varied the EMI shielding and dielectric properties of nanocomposite thin films The observed variations in EMI-SE and dielectric constant with frequency are discussed in terms of the dynamics of domain switching GRAPHICAL ABSTRACT

Fabrication of Biopolymer-Based Piezoelectric Thin Film From Chitosan Using Solvent Casting Method

The application of biopolymer in piezoelectric application provides a great potential to replace traditional piezoelectric substances like polyvinylidene fluoride (PVDF) and lead zirconate titanium (PZT), because of their biodegradability, biocompatibility, low toxicity properties and sustainable production. Chitosan, a natural polysaccharide has been found to fulfil all the characteristics and can be used safely for piezoelectric applications in agricultural, food industries and biomedical fields. This study aims to assess how piezoelectric characteristics are affected by different acid solvents and solvent casting volumes during chitosan thin film production. Chitosan thin film prepared using acetic acid and formic acid were fabricated using solvent casting method on petri dish at different volume of acids solvent. Chitosan thin films produced using acetic acid and 25 mL solvent loading provided the most significant mechanical quality factor (2.8). Moreover, the dissipation factor (0.80) was the lowest, indicating comparability to traditional thin PVDF film piezopolymer. Hence, thin chitosan films produced using acetic acid is proven to have the potential in piezoelectric application

Effects of solvents on synthesis of piezoelectric polyvinylidene fluoride trifluoroethylene thin films

• Polyvinylidene fluoride thin films were developed with multiple dissolving solvents. • High dipole moment solvents increased piezoelectric properties. • Propylene carbonate used to synthesize polyvinylidene fluoride. Polyvinylidene Fluoride (PVDF) and its co-polymer formulations, such as tri-fluoroethylene (TrFE) have been extensively researched as a thin flexible piezoelectric material for a wide range of applications, and new methods of synthesizing the material are continuously being investigated. Researchers have used various solvents to synthesize the PVDF film, yet the effects of these solvents on the piezoelectric properties have not been systematically investigated. The selection of an optimized solvent for polymer dissolution can affect film properties, which could lead to enhanced device performance for piezoelectric-based microsystems. Herein, several solvents were screened for the dissolution of PVDF-TrFE polymer to investigate the effect of solvents and to determine key properties of the solvents that influence the piezoelectric response, so further enhancements can be made in the future. This study investigated 14 different solvents with varying physicochemical properties. The thin films were characterized via X-ray diffraction and quasi-static piezometer measurements. This paper reports that the piezoelectric coefficient of the thin film was highly dependent on the solvent's dipole moment. Our observation revealed that the solvent with the highest dipole moment that was able to completely dissolve the PVDF-TrFE powder produced the film with the highest piezoelectric coefficient. The spin coated film decreased thickness with increasing spin speed, and the piezoelectric coefficient was not affected by the thickness of the film in the range of 1–5 μm.

Simultaneous measurement of two biological signals using a multi-layered polyvinylidene fluoride sensor

Cardiovascular and deep breathing diseases can be detected by measuring human signals such as heart rate, respiration, and blood pressure, which are important physiological parameters for accessing the state of the body. However, conventionally, heart and respiration rates are monitored using different sensors, which is cumbersome and can further increase the psychological burden on patients. To address these issues, this report proposes a sensor consisting of two stacked elements that can simultaneously measure heart and respiration rates. The two signals received can be expressed separately as heart and respiration rates after signal processing. The two stacked elements are composed of polyvinylidene fluoride thin film bonded to a polydimethylsiloxane substrate. One element (element 1) measures movement related to the heart, and the other (element 2) measures movement related to breathing. Elements 1 and 2 were experimentally observed to have sensitivities of 0.163 V/N and 0.209 V/N, respectively. In addition, the proposed system was compared with a commercial digital heart rate and respiration rate measurement instrument and was verified to be effective for simultaneous measurement of human vital signals with multiple sensors. In addition, the proposed system is flexible, lightweight, and inexpensive, making it convenient and economical.

Preparation and properties of antibacterial PVDF composite thin films

As medical dressings, polyvinylidene fluoride (PVDF) thin films loaded with antimicrobial agents offer excellent wound infection control. In this study, PVDF/tea polyphenol (TPs) and PVDF/TPs/Ag composite thin films were prepared by electrically assisted three-dimensional (3D) printing method. The surface morphology, hydrophilicity, and antibacterial properties of the composite thin films were studied. The results showed that the presence of appropriate amount of TPs promoted the crystallinity and β-phase content of the PVDF thin films, and TPs played an important role in the formation of abundant holes on the surface of PVDF films. It facilitated the deposition of silver nanoparticles on the surface of PVDF thin film and improved the uniformity of their distribution. The Escherichia coli (E. coli) inhibition rate of the PVDF/TPs composite thin film reached 97.22%. The antibacterial activity of this composite thin film improved significantly after the deposition of silver nanoparticles, and the E. coli inhibition rate of the PVDF/TPs/Ag composite thin film was 99.58%.

Research on Measurement of Transformer Short-Circuit Force Using Piezoelectric Thin Film Polyvinylidene Fluoride Sensor

This paper presents a newly designed piezoelectric thin film polyvinylidene fluoride (PVDF) sensor that is able to measure short-circuit force directly in a short-circuit test. The sensor, with its advantages of high sensitivity, thin shape and shock-resistant, could measure the axial and radial short-circuit force which is usually difficult to measure due to large voltage and small gap between transformer windings during a short-circuit test, and thus provides a good way to study the ability of transformers to withstand short circuit, in which case many transformer accidents are caused. In the first part the working principle of PVDF sensor and the design of PVDF sensor in transformers are described. The following part introduces the calculation and simulation of the sensor and the short-circuit force. A real short-circuit test with PVDF sensor is then recorded and analyzed in the following part. And it is finally concluded that the piezoelectric thin film PVDF sensor is proved to have high accuracy in the measurement of the short-circuit force of transformer.

Structural and microstructural analysis of spin-coated PVDF thin films

In present work, semi-crystalline polyvinylidene fluoride (PVDF) films of 5 wt%, 10 wt%, and 15 wt% PVDF solution is deposited on the glass substrate by spin coating technique at 500, 1000, and 1500 rpm speed. For deposition of the film, the polymeric solution is prepared by dissolving PVDF powder in the polar solvent of N,N-dimethylformamide solvent. The effect of different PVDF content and spin coating speed on the microstructural evolutions in the produced film is investigated by using FE-SEM, AFM, and FTIR spectrometer. The optical properties of the film are also investigated by the UV-vis spectrometer.