Piezoelectric Polyvinylidene Fluoride Research Articles

Experimental Study of Taper Shape Bistable Beam for Improved Vibration Energy Harvesting

Abstract 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.

Re-usable Cd0.9Zn0.1S-ZnO@C/PVDF piezo-photocatalytic film with exceptional hydrogen evolution capability triggered by the synergetic advantages of piezoelectricity and S-Scheme heterojunction

Piezoelectric materials have advantages of fine-tuning photocatalytic performance through harvesting mechanical energy and open a new avenue in facilitating green catalytic reaction. Herein, polyvinylidene fluoride (PVDF), a flexible piezoelectric material, was introduced to synthesize a novel Cd0.9Zn0.1S-ZnO@C/PVDF (CZS-ZO@C/PVDF) piezo-photocatalytic film by spin coating and immersion phase conversion method. Benefiting from the piezoelectricity of PVDF and the internal electric field (IEF) of CZS-ZO@C Step-scheme (S-Scheme) heterojunction, CZS-ZO@C/PVDF was able to induce a hydrogen generation rate of 34.9 mmol g−1 h−1 activated by ultrasound and visible light (U-L), which is ∼17.5 times of Cd0.9Zn0.1S/PVDF (CZS/PVDF) and ∼7.4 times of the photocatalysis rate activated by visible light only (L). Piezoelectric measurements and COMSOL simulation illustrated the excellent piezoelectricity of CZS-ZO@C/PVDF film, which exhibits a piezoelectric coefficient (d33) of 9.9 pm V−1 and a piezoelectric potential of 874 mV (under 0.5 MPa). The reaction mechanism for the exceptional piezo-photocatalytic performance was finally disclosed through density functional theory (DFT) calculation and electrochemical tests. This study enriches the application scope of piezoelectric materials in sustainable energy catalysis and provides a new direction to develop efficient piezoelectric photocatalysts.

Polyvinylidene Fluoride Nanocomposites as Piezoelectric Nanogenerator: Properties, Fabrication and Market Applications

Depletion of fossil fuels and increase in pollution through chemical batteries trigger the development of self‐powered devices based on flexible piezoelectric nanogenerators (PNG). Biocompatible piezoelectric polyvinylidene fluoride (PVDF) nanocomposites merged with piezoelectric fillers like ZnO, KNN, and BaTiO3 reproduce amended piezoelectric current, contributing to the safe application as biosensors and flexible industrial devices. Optimized loading, precise selection, and variating the surface chemistry of piezoelectric filler, along with fabrication schemes comprising different structural configurations of composites, considerably influence its potential for application as an energy harvester. Also, optimized processing condition upgrades dielectric constant and energy storage density, and reduces dielectric loss, thereby plummeting energy dissipation even after prolonged usage. Consequently, this article reviews the principles, properties, fabrication techniques, and market application of PVDF composites. A detailed relationship of significant electrical properties of PVDF composites with its fabrication methods and (piezoelectric parameters of fabricated PVDF composites with reported real‐life wearable, implantable, and industrial‐based portable piezoelectric devices are discussed in detail along with tabulated data for a clear understanding of structure–property relationship. Again, the market strategy for establishing flexible PVDF composite as a PNG has been discussed. A piece of in‐depth knowledge is provided for procuring affordable futuristic large‐scale PVDF‐based nanogenerators exhibiting affordable market worth.

Research progress of piezoelectric polymer PVDF in sound absorption technology

Owing to its impedance properties and piezoelectric effect, the piezoelectric polymer polyvinylidene fluoride (PVDF) finds application in the field of noise control. Traditional sound-absorbing materials have gradually fallen short of the demands of sound-absorbing functionality and environmental adaptability in today’s increasingly acute noise pollution environment. When PVDF is added to sound absorption, materials or structures have an additional loss path for the conversion of sound energy to electric energy. This helps to increase the low-frequency sound absorption band and improve low-frequency sound absorption performance. Through the action of viscosity, friction, relaxation, piezoelectric effect, and dielectric loss, the sound energy in the passive sound-absorbing material containing PVDF is transformed into energy dissipation in the form of heat energy, electric energy, and so on under the matching of PVDF low impedance. In active control, secondary sound and force sources can be supplied by PVDF-based transducers and actuators to reduce noise. This paper first provides an overview of the piezoelectric characteristics of β-phase PVDF and its optimization techniques. It then goes on to discuss the use of PVDF in passive sound-absorbing materials, active controls, and hybrid sound absorption systems. Finally, it summarizes the benefits, issues that still need to be resolved, and future directions for these three noise reduction techniques.

Futuristic Alzheimer's therapy: acoustic-stimulated piezoelectric nanospheres for amyloid reduction.

The degeneration of neurons due to the accumulation of misfolded amyloid aggregates in the central nervous system (CNS) is a fundamental neuropathology of Alzheimer's disease (AD). It is believed that dislodging/clearing these amyloid aggregates from the neuronal tissues could lead to a potential cure for AD. In the present work, we explored biocompatible polydopamine-coated piezoelectric polyvinylidene fluoride (DPVDF) nanospheres as acoustic stimulus-triggered anti-fibrillating and anti-amyloid agents. The nanospheres were tested against two model amyloidogenic peptides, including the reductionist model-based amyloidogenic dipeptide, diphenylalanine, and the amyloid polypeptide, amyloid beta (Aβ42). Our results revealed that DPVDF nanospheres could effectively disassemble the model peptide-derived amyloid fibrils under suitable acoustic stimulation. In vitro studies also showed that the stimulus activated DPVDF nanospheres could efficiently alleviate the neurotoxicity of FF fibrils as exemplified in neuroblastoma, SHSY5Y, cells. Studies carried out in animal models further validated that the nanospheres could dislodge amyloid aggregates in vivo and also help the animals regain their cognitive behavior. Thus, these acoustic stimuli-activated nanospheres could serve as a novel class of disease-modifying nanomaterials for non-invasive electro-chemotherapy of Alzheimer's disease.

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.

Self-poled PVDF/recycled cellulose composite fibers utilizing cellulose nanocrystals to induce PVDF β-phase formation through wet-spinning as a flexible fabric piezoelectric sensor

In general, PVDF (Polyvinylidene fluoride) needs polarization treatment to exhibit its piezoelectric properties. Introducing nanofillers or applying stretching during the processing can promote the β-phase transformation in PVDF, achieving self-polarization. Herein, by incorporation of cellulose nanocrystals (CNCs), continuous β-phase enriched PVDF/cellulose composite fibers are prepared via wet spinning and drawing, in which the cellulose is recycled from waste cotton textiles to improve the wet spinnability of PVDF and reduce the cost. The obtained composite fibers are woven into fabrics and subsequently assembled into a flexible sensor, exhibiting excellent piezoelectric performance (d33 = 26.2 pC/N) without requiring additional polarization treatment. It generates an open-circuit voltage of 12 V and a short-circuit current of 100nA, much higher than those of the previously reported piezoelectric PVDF sensors with high-voltage polarization. This fabric-based flexible sensor also exhibits notable characteristics, including stable output signals and heightened sensitivity, thereby fulfilling the demands for monitoring both minute and extensive human movements. Furthermore, it shows great potential for widespread use in sound sensing for human-machine interfaces. The self-poled PVDF composite fibers offer the advantage of being easily woven together with other fiber materials, which contributes towards the development of self-powered flexible piezoelectric fabric sensors.

Optimizing solvent dipole moment enables PVDF to improve piezoelectric performance

The all-trans conformation (β-phase) possesses a significant impact on the piezoelectric polymer polyvinylidene fluoride (PVDF). Inducing more molecular chain [−CH2−CF2−]n to form all-trans conformation is one of the biggest obstacles for manufacturing high-performance piezoelectric sensing devices. Herein, the continuous vacuum technology is used to modulate the polarity of binary solvents by the proportion of the lower solvent. The regulated solvent forms a high dipole moment, an interaction between the dipole of β-phase and the dipole moment makes the phase reversal in PVDF. Fourier transform infrared spectroscopy, piezoelectric constant test and other characterization results show that when the weakly polar acetone and the strongly polar solvent DMF reach a ratio of 4:6, the pure PVDF film possesses high piezoelectricity (d 33 ∼ −44.8 pC N−1) and strong self-polarization. Additionally, the A4D6 device exhibits high sensitivity (S 1 = 0.182 V/N, 0.5 N ∼ 30 N), driven capability (0.49 mW m−2), and reliability during the electrical tests as a pressure device. This work provides an effective and cost-effective route of optimizing the solvent’s polarity to improve the piezoelectric characteristics of the polymer.

Ultrasound-Activated Piezoelectric Polyvinylidene Fluoride-Trifluoroethylene Scaffolds for Tissue Engineering Applications.

Severe peripheral nervous system (PNS) injuries have limited options for therapeutic solutions to regain functional recovery. This can be attributed in part to the lack of regeneration pathways promoted by recapitulating chemical, physical, and electrical cues to direct nerve guidance. To address this, we examined ultrasonic stimulation of a piezoelectric polyvinylidene fluoride-triflouroethylene (PVDF-TrFE) scaffold as a potentially clinically relevant therapy for PNS regeneration. Owing to the piezoelectric modality of PVDF-TrFE, we hypothesize that ultrasound stimulation will activate the scaffold to electrically stimulate cells in response to the mechanical deformation mediated by sound waves. Biocompatible PVDF-TrFE scaffolds were fabricated to be used as an ultrasound-activated, piezoelectric biomaterial to enhance cellular activity for PNS applications. NIH-3T3 fibroblasts were cultured on PVDF-TrFE nanofibers and stimulated with low-, medium-, or high-powered ultrasound. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays were performed on fibroblasts to measure the metabolic activity of the cells following stimulation. MTT assays showed that ultrasound-stimulated fibroblasts on PVDF-TrFE scaffolds had increased metabolic activity as power was increased, whereas on plain polystyrene, an opposite trend was observed where cells had a decreased metabolic activity with ascending levels of ultrasound power. Ultrasound-stimulated PVDF-TrFE nanofibers hold exciting potential as a therapy for PNS injuries by promoting increased metabolic activity and proliferation. The ability to noninvasively stimulate implantable piezoelectric nanofibers to promote mechanical and electrical stimulation for nerve repair offers a promising benefit to severe trauma patients.

PVDF‐Based Flexible Piezoelectric Tactile Sensors: Review

AbstractWith the advent of the intelligence era, flexible piezoelectric tactile sensors are the key components for sensing information and sending signals. The performance parameters of piezoelectric sensors are closely related to the selection of piezoelectric materials. Compared with conventional piezoelectric materials, polyvinylidene fluoride (PVDF) has significant advantages in flexibility, stretchability, chemical stability, electromechanical conversion, ease of use, and acoustic propagation impedance. As a result, PVDF has become a popular topic of research. This paper introduces the working principle of piezoelectric materials and flexible piezoelectric sensors based on PVDF materials and details the research progress of different materials based on PVDF for the preparation of flexible piezoelectric tactile sensors, such as: PVDF and its copolymers for the preparation of flexible piezoelectric sensors and PVDF doped with other functional materials for the preparation of flexible piezoelectric sensors. In this paper, the advantages and disadvantages of different materials and the development prospects of PVDF flexible piezoelectric sensors are summarized to provide some insights for high‐performance flexible PVDF piezoelectric sensors.

Electrospinning of Highly Bi-Oriented Flexible Piezoelectric Nanofibers for Anisotropic-Responsive Intelligent Sensing.

Flexible piezoelectric energy harvesters (PEHs) have gained substantial attention owing to their wearability, breathability, and sustainable self-powered supply. However, existing film PEHs cannot identify forces in different bending directions, limiting their applications in wearable electronics and artificial intelligence. This study constructs a fabric PEH for the first time by introducing piezoelectric anisotropic BaTi2 O5 nanorods (BT2-nr) into piezoelectric polyvinylidene fluoride (PVDF) nanofibers with a bi-oriented architecture, in which BT2-nr uniformly aligns in the PVDF nanofiber during electrospinning. The dual-orientation feature endows the flexible PEH with anisotropy, which can sensitively identify the forces at different bending directions (e.g., bent vertically, parallelly, or twisted by 45° along the fiber orientations). Simultaneously, the composite PVDF/BT2 PEH containing 15wt.% BT2-nr delivers an optimal piezoelectric output of 31.2V with a high sensitivity of 5.22V N-1 . The developed anisotropic PEH can be used as a self-powered pressure sensor for multimodal intelligent biomonitoring of human movement. This study provides a feasible strategy for fabricating self-powered flexible PEHs with high electromechanical conversion efficiency and multifunctionality for wearable piezoelectric pressure sensors.

Boosting Piezoelectricity by 3D Printing PVDF‐MoS2 Composite as a Conformal and High‐Sensitivity Piezoelectric Sensor

AbstractAdditively manufactured flexible and high‐performance piezoelectric devices are highly desirable for sensing and energy harvesting of 3D conformal structures. Herein, the study reports a significantly enhanced piezoelectricity in polyvinylidene fluoride (PVDF) achieved through the in situ dipole alignment of PVDF within PVDF‐2D molybdenum disulfide (2D MoS2) composite by 3D printing. The shear stress‐induced dipole poling of PVDF and 2D MoS2 alignment are harnessed during 3D printing to boost piezoelectricity without requiring a post‐poling process. The results show a remarkable, more than the eight‐fold increment in the piezoelectric coefficient (d33) for 3D printed PVDF‐8wt.% MoS2 composite over cast neat PVDF. The underlying mechanism of piezoelectric property enhancement is attributed to the increased volume fraction of β phase in PVDF, filler fraction, heterogeneous strain distribution around PVDF‐MoS2 interfaces, and strain transfer to the nanofillers as confirmed by microstructural analysis and finite element simulation. These results provide a promising route to design and fabricate high‐performance 3D piezoelectric devices via 3D printing for next‐generation sensors and mechanical–electronic conformal devices.

具有柔性和压电性的超薄Janus纳米纤维敷料用于伤口愈合

The healing process of infected skin lesions is often delayed by many factors including bacterial infection, excessive accumulation of wound exudate, poor local perfusion, and low cell recruitment. Development of wound dressing for efficient wound management and promotion of wound healing is a great challenge. Herein, we constructed a Janus nanofiber dressing with the comprehensive capacities of bacterial killing, piezoelectrical stimulation for promoting fibroblast migration, and wound exudate removal via unidirectional liquid delivery. The rationally designed Janus nanofibrous dressing with ultrathin, flexible, breathable, and piezoelectric characteristics is fabricated via the facile layer-by-layer electrostatic spinning technology. The hydrophilic layer of the dressing is composed of randomly arranged polycaprolactone/gelatin (PCL/Gel) nanofibers, while the hydrophobic layer consists of well-aligned Ag nanoparticles (Ag NPs)-doped piezoelectric polyvinylidene fluoride (PVDF/Ag) nanofibers. The in vitro and in vivo experimental results demonstrate that the Janus dressing can not only drain excess wound exudate out of the wound unidirectionally and kill local bacteria, but also generate dynamic piezopotential under normal body motions to promote fibroblast proliferation and migration, collagen deposition, angiogenesis, and re-epithelialization, which accelerates rapid wound healing on mice. The smart Janus dressing will provide a new approach for acceleration of wound healing and wound management.

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.

Synthesis and characterization of biphasic layered structure composite with simultaneous electroconductive and piezoelectric behavior as a scaffold for bone tissue engineering

AbstractIn recent years, materials with piezoelectric and electroconductive behavior have been thought interesting and important to be used for bone scaffolds due to their potential in mimicking the bone tissues. In the present work, attempts have been made to prepare three‐dimensional laminated scaffolds by means of embedding the piezoelectric polyvinylidene fluoride (PVDF)/polylactic acid (PLA) electrospun nanofibrous mats into the electroconductive porous oxidized alginate (ADA)/gelatin/polypyrrole‐graft‐gelatin (PPy‐g‐gelatin) hydrogel precursor structure to obtain a biphasic layered structure (a fiber‐hydrogel scaffold). The morphology, tensile strength, β‐phase contents, and crystallinity of the fibers are evaluated. The compressive modulus of the electrospun fiber‐hydrogel composites (32.72 MPa) shows to be much higher than the neat hydrogel (0.01 MPa). The prepared composites present high electrical conductivity (1.8 S m−1) and piezoelectric coefficient (1.61 fC N−1). By incorporating the fibers into the hydrogel structure, the cross‐link density of the composite is increased. The swelling ratio, porosity, and rate of biodegradation of the fabricated composites are also investigated. Moreover, good biocompatibility of human osteosarcoma cells attached to the PVDF/PLA nanofibers‐ADA/gelatin/PPy‐g‐gelatin hydrogel scaffold is evidenced by alkaline phosphatase assay, alizarin red and hematoxylin and eosin staining, and osteogenic gene expression evaluation. The prepared osteon‐mimetic samples with the synergized features of piezoelectricity and electrical conductivity can potentially be used as three‐dimensional scaffolds for bone tissue engineering.

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.

Enhanced bone regeneration via ZIF-8 decorated hierarchical polyvinylidene fluoride piezoelectric foam nanogenerator: Coupling of bioelectricity, angiogenesis, and osteogenesis

Piezoelectric biomaterials are advantageous in terms of easy generation of transduced bioelectrical signals to skeleton systems in response to body movements or external stimulations. In the bone formation process, the coupling of angiogenesis-osteogenesis is crucial but the effect of piezoelectric biomaterials on angiogenesis and mechanism of stress-transformed electrical signals affecting vascular cells remain elusive. In this work, hierarchically architected polyvinylidene fluoride (PVDF) foam fabricated by solid-state shearing milling was further decorated with ZIF-8 nanocrystals. The unique hierarchical porous structure realizes stable voltage outputs up to 10 V without polarization. The electric potential of piezoelectric PVDF affected molecular trajectory of Zn2+ released from ZIF-8, leading to Zn2+ enrichment around the PVDF surface. Under piezoelectric condition, PVDF/ZIF-8 foams promoted in-vitro angiogenic and osteogenic activity as well as antibacterial effect. Upon calvarium and femur defect repair, PVDF/ZIF-8 piezoelectric foams also guided vascularized bone regeneration through micro-current stimulation and Zn2+ enrichment. RNA-seq demonstrated PVDF/ZIF-8 piezoelectric foam mainly up-regulated ATP coupled cation transmembrane transportation in vascular endothelial cells, which enhanced cellular uptake of Zn2+, indicating the synergistic effect of piezoelectric PVDF and bioactive ZIF-8. This work offers a preliminary explanation for mechanism of angiogenesis-osteogenesis coupling of PVDF/ZIF-8 foam nanogenerator and provides a valuable complement to clinical treatment strategies for bone defect repair.

An Umbo Microphone for Fully-Implantable Assistive Hearing Devices

This article presents an implantable microphone for sensing the displacement of the umbo, the end of the malleus where it attaches to the center tip of the cone-shaped tympanic membrane. The sensor comprises a piezoelectric polyvinylidene fluoride (PVDF) film with copper–nickel electrodes suspended across a brass cylinder. The cylinder is oriented so that the umbo pushes on the film center, causing a static and acoustically driven dynamic film displacement. An amplifier filters the resulting piezoelectric charge to produce an output signal. The sensor enables the full implantation of assistive hearing devices, which can restore hearing without inhibiting the user’s lifestyle, while enabling better sound localization in noisy environments.

Structure-Property Relationship of Piezoelectric Properties in Zeolitic Imidazolate Frameworks: A Computational Study.

Metal-organic frameworks (MOFs) are a class of nanoporous crystalline materials with very high structural tunability. They possess a very low dielectric permittivity εr due to their porosity and hence are favorable for piezoelectric energy harvesting. Even though they have huge potential as piezoelectric materials, a detailed analysis and structure-property relationship of the piezoelectric properties in MOFs are lacking so far. This work focuses on a class of cubic non-centrosymmetric MOFs, namely, zeolitic imidazolate frameworks (ZIFs) to rationalize how the variation of different building blocks of the structure, that is, metal node and linker substituents affect the piezoelectric constants. The piezoelectric tensor for the ZIFs is computed from ab initio theoretical methods. From the calculations, we analyze the different contributions to the final piezoelectric constant d14, namely, the clamped ion (e140) and the internal strain (e14int) contributions and the mechanical properties. For the studied ZIFs, even though e14 (e140 + e14int) is similar for all ZIFs, the resultant piezoelectric coefficient d14 calculated from piezoelectric constant e14 and elastic compliance constant s44 varies significantly among the different structures. It is the largest for CdIF-1 (Cd2+ and -CH3 linker substituent). This is mainly due to the higher elasticity or flexibility of the framework. Interestingly, the magnitude of d14 for CdIF-1 is higher than II-VI inorganic piezoelectrics and of a similar magnitude as the quintessential piezoelectric polymer polyvinylidene fluoride.

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.