Electrospun scaffolds offer a promising platform for immune-instructive materials, but stable and modular functionalization with bioactive signals remains a technical challenge. Here, we develop a surface coating strategy for electrospun scaffolds that consist of poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), a piezoelectric polymer, using electrostatic adsorption of charged nanoparticles. We show that under certain conditions, these piezoelectric scaffolds are suitable substrates for electrostatic self-assembly, and that the density of nanoparticle coatings can be tuned by adjusting buffer pH, ionic strength, and nanoparticle concentration. This approach enables robust and uniform coating of both polymeric nanoparticles and soft nanocarriers such as liposomes, without requiring covalent surface modification. Liposome-coated scaffolds are cytocompatible with adherent epithelial and suspension immune cells and support lipid exchange at the cell-material interface. Using a supramolecular tethering strategy, we use liposome coatings to present interleukin-15 (IL-15) from the scaffold surface and demonstrate localized, sustained cytokine signaling. Together, these findings establish a modular approach for post-fabrication, noncovalent scaffold functionalization with bioactive nanocarriers, offering new opportunities for tissue and immune engineering.

The development of efficient, flexible, and sustainable energy-harvesting technologies is critical for powering self-sufficient wearable electronics, biomedical sensors, and remote IoT systems. In this study, we present an advanced auxetic laminar composite architecture that integrates piezoelectric polymer films—specifically P(VDF-TrFE) and P(VDF-TrFE-CTFE)—with re-entrant honeycomb substrates fabricated using a UV-curable resin. The negative Poisson’s ratio (NPR) behavior of auxetic structures was strategically employed to amplify in-plane mechanical strain in the active piezoelectric layers, enhancing voltage output under uniaxial loading. The electrospun nanofibers exhibited uniform, bead-free morphologies with preferential β-phase crystallinity, confirmed via SEM and wide-angle X-ray diffraction (WAXD). Finite element simulations revealed strong stress concentration at re-entrant hinges and vertical struts, with the degree of auxetic deformation increasing at larger monomer angles (55–65°) and thicker substrates. Digital image correlation (DIC) analysis confirmed consistent deformation behavior and validated simulated strain fields. Composite structures incorporating 5 mm-thick auxetic substrates and P(VDF-TrFE) films demonstrated superior mechanical strength, enhanced interfacial stress transfer, and significantly improved voltage response compared to P(VDF-TrFE-CTFE)-based systems. Experimental results showed that induced piezoelectric voltage increased nonlinearly with applied force and excitation frequency, with P(VDF-TrFE) achieving up to ~250% output enhancement. Simulated voltage outputs were in close agreement with experimental trends, supporting the design rationale. This work demonstrates a scalable, low-toxicity, and recyclable design for flexible piezoelectric harvesters using mechanical metamaterials. The integration of auxetic geometries with optimized piezoelectric polymers enables high sensitivity and tunable mechanical-electrical coupling, aligning with sustainable development goals. These findings provide valuable insights for designing next-generation flexible power sources for green energy applications.

Flexible piezoelectric sensors represent a particularly challenging yet extremely promising class of sensing devices, capable of enabling a wide spectrum of innovative applications across multiple fields. Due to their wide frequency range, they can be applied in wearable technologies, biomedical devices, soft robotics and structural health monitoring. In fact, such sensors can be strategically employed to provide proprioceptive feedback to passive structures, e.g. robotic joints or mechanical components of different thicknesses, helping to monitor and to perfect their movements and deformations. Moreover, when produced via Additive Manufacturing (AM), they can be easily tailored to fit different geometries and scales.AM technologies are indeed emerging as a highly promising solution for the on-demand, customizable fabrication of the next generation of flexible piezoelectric devices. Among the various AM techniques, Inkjet Printing (IJP) stands out as particularly advantageous. This is due to its ability to deposit functional materials in a non-contact, digitally controlled, scalable, and cost-effective manner. Furthermore, IJP is compatible with a broad range of functional inks typically used in the fabrication of piezopolymer-based sensors [1].In recent years, Polyvinylidene Fluoride, and in particular its copolymer with Trifluoroethylene P(VDF-TrFE), has been exploited as one of the most promising piezopolymers for the next-generation of sensing devices. Its remarkable piezoelectric coefficient, ease of processing, and biocompatibility put it in a top position for research in this field. The combination of this material and AM results in high processing scalability and leads to a unique set of desirable features: high mechanical flexibility, inherent biocompatibility, low weight, ease of fabrication as well as excellent sensitivity to mechanical stimuli without the need of a power supply [2]. These properties are fundamental for applications where traditional rigid sensors would fail or underperform. Hence, inkjet-printed flexible devices based on piezoelectric polymers are rapidly gaining attention in the next-generation sensors’ landscape.The present study explores the design, computational simulation, fabrication and initial performance assessment of a fully inkjet-printed piezoelectric sensor, specifically engineered for applications involving large mechanical deformations. The innovation introduced in this work lies not only in the exclusive combination of materials used, carefully selected to enhance piezoelectric response and mechanical durability, but also in the application of IJP as a manufacturing strategy for all the functional layers present in the device. Preliminary results confirm the feasibility and functionality of the proposed approach, showing that the sensor is capable of detecting dynamic and static strain with high sensitivity, even under significant bending or stretching conditions. The sensor maintains its performance without mechanical delamination, giving a stable and repeatable output signal Vpp ≈ 850 mV under cyclic bending. These findings underscore the potential of this novel materials/process synergy for the development of next-generation, low-cost, and highly adaptable piezoelectric sensors.[1] D. Thuah et al., J. Mater. Chem. C 5, 9963-9966 (2017).[2] F. Narita et al., Adv. Eng. Mater. 20, 1700743 (2018).

Abstract The scaffold for tissue engineering not only require good biocompatibility, mechanical properties and appropriate structure, but also should actively participate in biophysical and biochemical processes to accelerate tissue repair. Piezoelectric scaffold can generate electrical activity when deformed, which constructs an electrochemical microenvironment for inducing cell signaling pathways and facilitating tissue regeneration, attracting extensive attention in tissue engineering. Herein, piezoelectric materials used in tissue engineering, including piezoelectric ceramics, synthetic piezoelectric polymers and natural biological piezoelectric materials are systematically summarized, and their advantages and limitations are analyzed. As for piezoelectric scaffold, the piezoelectric properties mainly stem from the asymmetric crystal structure of materials and the directional arrangement of internal dipoles, which is highly dependent on the fabrication and post-treatment strategies. Therefore, the fabrication techniques of piezoelectric scaffold, covering both traditional fabrication techniques and additive manufacturing techniques are detailedly introduced. Besides, rational structural design of piezoelectric scaffold can alter strain transmission pathways and charge distribution, or add new operational modes to regulate piezoelectric properties. Thereby, the piezoelectric metamaterials, micro/nanostructures, porous structures, heterogeneous structures and biomimetic structures are comprehensively summarized. Additionally, the functions of piezoelectric scaffold for tissue engineering application in terms of bone regeneration, neural regeneration, antibacterial activity and intelligent sensing are reviewed. Finally, the challenges and future research directions of piezoelectric scaffold are discussed.

Smart sensor networks play important roles in structural monitoring, health diagnosis, and data transmission. Given their extensive distributed energy requirements, piezoelectric energy harvesting, which aims to convert mechanical vibrational energy into electrical power, can serve as a viable alternative or supplement to power supplies owing to its compact size, high power density, and excellent stability. Piezoelectric energy harvesting involves three key components: piezoelectric materials responsible for mechanical-to-electrical energy conversion, mechanical structures enabling mechanical-to-mechanical energy transmission, and power-management systems used to efficiently extract electrical energy. For electromechanical conversion, state-of-the-art piezoelectric materials, including crystals, ceramics, polymers, and composites, are analyzed. Regarding mechanical energy transmission, the focus is on methodologies to achieve high power output, wide bandwidth, and multi-directional vibration capability. Several widely adopted electrical circuits are comprehensively reviewed in terms of power management. From an application perspective, practical energy harvesters are categorized into magneto-mechano-electric, fluid-based, biomechanical, and ultrasound-induced types. Additionally, future theoretical and practical challenges in piezoelectric energy harvesting are discussed.

The promising outcome of Bone Tissue Engineering (BTE) via scaffolds for treating segmental bone defects (SBDs) has led the interdisciplinary field of Materials Science to take a new turn and explore innovative biomaterials that enhance tissue regeneration. The most recent advancement is the application of electrical stimulation with the use of conductive and piezoelectric biomaterials to develop conductive and electroactive (EA) scaffolds that activate osteoblast formation, leading to a significantly faster and more robust bone healing process. Researchers have explored plenty of biomaterials and scaffold fabrication techniques. This article presents a comprehensive review of the popular biomaterials that include Conductive Polymers (PANI, Poly-pyrrole, PEDOT), Piezoelectric Polymers (PVDF, TrFE, PLLA, PAs), Metallic Nanoparticles (NPs) (Ag, TiO2), and Carbon-based NPs (CNTs, Graphene, Graphene Oxide) used for the development of conductive and EA biocompatible scaffolds. Various innovative conductive and electroactive scaffold fabricating methods, like 3D printing, bio-printing, electrospinning, etc., that precisely command over the conductive filler distribution, porosity, and pore size interconnectivity are highlighted. Tests explored by researchers for investigating the conductive and piezoelectric properties of the developed scaffolds and their osteogenic potential (in vitro and invivo) are also presented. Apart from this, standard protocols for the conduction of these tests, regulatory pathways, scope for clinical translations, and their respective challenges have been reviewed. Most importantly, the review not only focuses on the material versatility and fabrication techniques but also critically analyzes the challenges involved in optimizing the biomaterials and fabrication parameters to develop bone scaffolds with the best-optimized physicochemical, mechanical, biological, and conductive properties.

A piezoelectric polymer coating on percutaneous hearing implants as a novel, device-powered antibacterial strategy

In this work, we investigated the use of a piezoelectric flexible device for energy harvesting. The main goal of the study was to fill the nanostructured pores of anodic aluminum oxide (AAO) films with piezoelectric polymer (PVDF-TrFE) via a modified conventional screen printing technique using blade printing. In this way, it is possible to obtain a composite from nanostructured thin films of polymer nanorods that shows improved charge generation ability compared to other non-nanostructured composites or pure (non-composite) aluminum with similar dimensions. This behavior is due to the effect of the highly developed surface of the material used to fill in the AAO nanopore template and its ability to withstand the application of higher mechanical loads to the structured piezoelectric material during deformation. The contact blade print filling technique can produce nanostructured piezoelectric polymer films with precise geometric parameters in terms of thickness and nanorod diameters, at around 200 nm, and a length of 12 μm. At a low frequency of 17 Hz, the highest root-mean-square (RMS) voltage generated using the nanostructured AAO/PVDF-TrFE sample with aluminum electrodes was around 395 mV. At high frequencies above 1700 Hz, the highest RMS voltage generated using the nanostructured AAO/PVDF-TrFE sample with gold electrodes was around 680 mV. The RMS voltage generated using a uniform (non-nanostructured) layer of PVDF-TrFE was 15% lower across the whole frequency range.

Abstract Electrospinning is a simple and versatile technique for producing nanofibers. However, conventional single-nozzle devices have inherent limitations in preparing functional composite nanofiber materials. Although dual-nozzle electrospinning provides a direct method for fabricating composite fibers, the integration of dual nozzles into the electrospinning system distorts the electric field distribution. This distortion induces Coulomb repulsion between the uniformly charged jets, resulting in an uneven distribution of heterogeneous fibers in the composite membrane. This unevenness significantly compromises the structural integrity of the material. In this study, we systematically developed an electrospinning simulation model for electric field analysis and jet trajectory prediction. We elucidated the repulsion mechanism between electric field heterogeneity and Coulomb forces in a single-power-supply dual-nozzle system and proposed a dynamic scanning deposition strategy to address the technical challenges of producing heterogeneous fiber composites. This strategy enabled the formation of composite piezoelectric and conductive polymer nanofibers. The resulting composite nanofibers exhibit both high piezoelectricity (d33 = 21.7 pC/N) and electrical conductivity (0.0646 S/m), confirming the effectiveness of the dynamic scanning deposition approach. Supported by the experimental validation of simulation reliability, this study provides a theoretical basis for optimizing the single-power-supply dual-nozzle electrospinning process to produce heterogeneous nanofiber composites.

ABSTRACT Piezoelectric materials convert mechanical energy into electrical energy and are used as sensors, actuators, and energy harvesters in Industry 4.0. Polymer nanocomposites with adjustable performance and affordability could transform piezoelectric technology. Fluoropolymers like poly(vinylidene fluoride) (PVDF) and its copolymers are common in developing these composites with various nanoparticles. Zinc oxide (ZnO) is promising due to its non‐centrosymmetric structure, high piezoelectric coefficient, and versatile nanostructure synthesis. This review covers recent trends in fabricating and optimizing piezoelectric polymer nanocomposites based on fluoropolymers and ZnO, including synthesis principles and advanced methods. It examines approaches to enhance piezoelectric and physical properties, emphasizing PVDF/ZnO composites' applications. The review also discusses challenges and future directions, serving as a resource for researchers and industry professionals aiming to improve piezoelectric materials for next‐generation use.

Rheumatoid Arthritis (RA) and Osteoarthritis (OA) are among the most impactful musculoskeletal disorders causing articular cartilage degradation, ultimately leading to loss of the joint functionality. Matrix-assisted Autologous Chondrocytes Implantation (MACI) is one of the most promising reconstructive techniques to treat chondral defects (CDs). MACI relies on a matrix cellularized with autologous chondrocytes implanted directly onto cartilage defects. Despite MACI's effectiveness, post-surgery rehabilitation remains a challenge, as it fails to induce the optimal mechanobiology necessary for an effective cartilage regeneration. Additionally, there is a significant patient-to-patient variability and the local loads occurring during rehabilitation might consequently vary greatly. We propose a personalized approach focused on the delivery local pro-regenerative mechanobiological cues to dramatically improve the cartilage restoration after MACI.We developed an innovative scaffold to be used as matrix in MACI, capable to enhance the cartilage repair by delivering in situ controlled, and personalized, mechanical cues triggering pro-regenerative cellular responses to embedded human articular chondrocytes (hACs). The scaffold relies on an electrospun matrix made of aligned fibers composed of PVDF-TrFE, a piezoelectric polymer, enriched with ferromagnetic Fe3O4 nanoparticles capable to confer magnetic properties to the scaffold. MNPs were simultaneously dispersed in the polymeric solution, and microfibers were collected onto a high-speed rotating collector to obtain an aligned micropattern, capable to give mechanical anisotropy to the scaffold. After cellularization with hACs, we subjected the scaffold to daily magnetic stimulation up to 14 days.The scaffold was highly responsive to external magnetic stimuli. In addition, hACs produced a type II collagen-rich extracellular matrix when cultured within the scaffolds subjected to magnetic stimulation. Remarkably, we observed an increase of cell viability, and of type II/type X collagen ratio.Our scaffold was able to provide pro-regenerative cues to hACs after mechanical cyclic deformations induced by repeated magnetic stimulations. Such an approach paves the way to an effective, and definitive therapeutic procedure for the treatment of chondral defects.

The growing demand for self-powered and flexible electronics has drawn attention to piezoelectric materials, capable of converting mechanical energy into usable electricity. Piezoelectric polymeric materials have gained significant attention due to their unique ability to generate electrical signals in response to mechanical deformation, coupled with their lightweight, flexible, and biocompatible nature. These features make them promising candidates for next-generation energy harvesting systems, especially in wearable technology, biomedical implants, and self-powered sensing devices. In this work, we studied the effect of incorporation of barium titanate (BTO) nanoparticles on the electrospun Polyvinylidene Fluoride (PVDF) and Polyvinylpyrrolidone (PVP) for energy harvesting properties. For this, we prepare a piezoelectric polymer (PVDF/BTO) and a non-piezoelectric polymer (PVP/BTO) nanocomposite and compare their energy harvesting properties. BTO nanoparticles were synthesized using a sol-gel method and dispersed in polymer matrices via electrospinning. Detailed structural, thermal, and dielectric characterizations were performed alongside electromechanical testing. Among the systems, the PVDF/BTO nanocomposite demonstrated the highest energy harvesting performance, delivering an output voltage of 3.8 V, current of 2.1 µA, and power of 7.98 µW under cyclic mechanical stress. The PVP/BTO nanofibers, although a non-piezoelectric polymer, demonstrated a moderate output current (1.3 µA) and output voltage (2.4 V), revealing the influence of PVP's dipolar interactions, marking their promising auxiliary role in nanocomposite engineering. On comparison with a non-piezoelectric polymer matrix, there is an increase of 83% performance for PVDF/BTO nanocomposite. These results were attributed to enhanced β-phase formation and interfacial polarization of PVDF, facilitated by the BTO dispersion. This work illustrates the promise of interface-optimized hybrid nanofibers in enabling high-output, flexible nanogenerators for wearable and self-powered technologies.

Artificial photoreceptors utilizing piezoelectric polymers and semiconductors can convert external mechanical deformations, forces, or changes in light into electrical signals, making them essential for advanced optoelectronic sensors and smart wearable devices. However, this approach faces several challenges, including slow response time, weak signal, and high power consumption. This study synthesizes a series of polyurethanes containing azobenzene-based photoisomer units and ionic-liquid-based dipole units (comprising loose cation-anion pairs) based on the nanophotoelectric effect, wherein ultraviolet light induces isomerization of photoisomer segments and generates dynamic dipoles, creating equal amounts of charges with opposite signs at the electrodes. The nanophotoelectric generator achieves open-circuit voltage of 37 V, short-circuit current of 265 µA, and rapid response time of 7.5 µs under UV illumination. Furthermore, 81 individual nanophotoelectric generators are integrated into a 9 × 9 pixel array for a machine-learning-assisted system to accurately (96.22%) recognize different items, like human vision; it simultaneously executes super-resolution refinement on the acquired pixel images, further improving the identification results. Precise, efficient intelligent object recognition is thus attained through material innovation, and a comprehensive system is established that encompasses azobenzene-ionic-liquid copolymer preparation, device assembly, integration, signal acquisition, and machine learning, offering novel insights into bionic visual recognition systems.

Dispersion spectrum and transient responses of guided waves in graphene platelet reinforced piezoelectric polymer composite plates

Piezoelectric polymer nanocomposites have attracted substantial interest due to their capability to combine the excellent piezoelectric properties of ceramics with the flexibility of polymers. This combination makes them highly suitable for applications in portable and wearable sensors, as well as energy harvesters. However, their performance is often hindered by inconsistent local piezoelectricity, which results from uneven nanofiller distribution and ineffective stress transfer at the nanofiller/polymer interfaces. Addressing these challenges necessitates improving the dispersibility of nanofillers and enhancing interfacial interactions between nanofillers and the polymer matrix. Additionally, increasing and/or arranging spontaneous polarization in nanofillers can enhance the overall piezoelectricity of nanocomposites, mitigating performance declines. Recent studies aimed at improving the performance of lead-free piezoelectric polymer nanocomposites through nanofiller modifications such as surface coating/decoration and chemical doping have been summarized. The proposed modes of performance enhancement by surface-coated and chemically doped nanofillers have been introduced and summarized. Finally, some suggestions and strategies for future research endeavors are presented.

Polymer-metal-organic framework (polymer-MOF) composites have garnered significant interest as polymers can enhance the processability and industrial applicability of MOFs. Thin films of these composites are particularly attractive for applications in sensing, separations, and flexible electronics. Solution shearing, a meniscus-guided coating technique, has emerged as a scalable process for fabricating thin films of MOFs, and can produce large-area films within minutes. In this study, we utilized solution shearing to fabricate composite thin films of a MOF UiO-66 and a piezoelectric polymer poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), investigating how polymer concentration during MOF synthesis and composite formation influences thin film properties, including crystallinity, surface coverage, and piezoelectric performance. Additionally, solid-state NMR spectroscopy was utilized to probe the interactions between P(VDF-TrFE) and UiO-66 in the composite. Evidence from solid-state NMR indicated polymer-MOF interactions, suggesting that the polymer strands are in close proximity to the UiO-66 pores, supporting a mixed surface coating and pore infiltration model. Furthermore, incorporating P(VDF-TrFE) enhanced the film's areal coverage from 70% to 100%. While the thermal conductivity remained essentially unchanged, the composite film showed an improved piezoelectric effect. The composite with 91 wt % P(VDF-TrFE) exhibited the highest output voltage of 9.1 V and a sensitivity of 0.26 V/N under applied pressure. This work demonstrates the potential of solution shearing as a scalable technique for fabricating polymer-MOF composite thin films.

ABSTRACT This work examines the fluid-structure interaction effects on the wave dispersion in smart sandwich doubly-curved shallow shells coupled with fluid, based on a novel quasi-3D shell theory. The doubly-curved shells consist of three composite layers. Graphene platelets are used to strengthen the piezoelectric polymer in the upper and bottom layers. The graphene platelets (GPLs) are graded or uniformly dispersed throughout the thickness. Five types of functionally graded (FG) graphene/piezoelectric doubly-curved shells are examined. While, the core layer is made of a negative Poisson's ratio structure. The fluid is assumed to act as a pressure on the shell. Based on the Bernoulli equation and velocity potential, the mathematical model of the fluid is yielded. Using a micromechanical model, the material parameters of the face layers are determined. Six equations of motion are derived using Hamilton's principle and a quasi-3D sinusoidal shell theory. These equations are then transformed into an eigenvalue problem using an analytical technique. A few comparative cases are presented in order to verify the results that were achieved. The effects of the graphene distribution type, shell curvatures, core thickness ratio, shallowness ratio, and fluid depth on the wave dispersion of a smart graphene/piezoelectric sandwich doubly-curved shallow shells with negative Poisson's ratio core coupled with fluid are demonstrated through a parametric investigation.

Continuous blood pressure monitoring based on improved multi-scale U-net assisted with piezoelectric polymer nanocomposite sensors

Poly(vinylidene fluoride) (PVDF) is a piezoelectric polymer, with the crystalline β-phase having the highest polarity among all its phases. A multistage transformation process is developed, using molecular dynamics simulations, to compute the free energy difference between α- and β-phases of PVDF. Methods of free energy perturbation and Jarzynski's equality were used to determine Helmholtz free energy change, ΔF, for the individual stages, from which the Gibbs free energy difference, ΔG, between the α- and β-phases was calculated. Infinitely large crystals modeled using periodic boundaries with 36 chains and 12 monomers in each chain were used for the study. All-atom simulations were performed with the force fields previously developed for PVDF. In concurrence with experimental observations, the α-phase was found to be thermodynamically more stable at normal temperature and pressure conditions. The β-phase was found to be more stable at high and low temperatures and high pressure.

Piezoelectric polymer composites, particularly polyvinylidene fluoride (PVDF) blended with barium titanate (BT), show promise for wearable technologies as both energy harvesters and haptic actuators. However, these composites typically exhibit limited electromechanical coupling and insufficient β-phase formation. This study presents a novel approach using ionic liquids (ILs) to enhance PVDF-based piezoelectric composite performance. Through solution-casting methods, we examined the effect of IL concentration on the structural, mechanical, and piezoelectric properties of PVDF/BT composites. Results demonstrate that the use of IL significantly improves β-phase crystallization in PVDF while enhancing electrical properties and mechanical flexibility, which are key requirements for effective energy harvesting and haptic feedback applications. The optimized composites show a 25% increase in β-phase content, enhanced flexibility, and a 100% improvement in piezoelectric voltage output compared to other more conventional PVDF/BT systems. The IL-modified composite exhibits superior piezoelectric response, generating an output voltage of 9 V and an output power of 40.1 µW under mechanical excitation and a displacement of 138 nm when subjected to 13 V peak-to-peak voltage, making it particularly suitable for haptic interfaces. These findings establish a pathway toward high-performance, flexible piezoelectric materials for multifunctional wearable applications in human–machine interfaces.