High performance piezocomposites for flexible device application

Participation of Polymer Materials in the Structure of Piezoelectric Composites

This review explores the integration of polymer materials into piezoelectric composite structures, focusing on their application in sensor technologies, and wearable electronics. Piezoelectric composites combining ceramic phases like BaTiO3, KNN, or PZT with polymers such as PVDF exhibit significant potential due to their enhanced flexibility, processability, and electrical performance. The synergy between the high piezoelectric sensitivity of ceramics and the mechanical flexibility of polymers enables the development of advanced materials for biomedical devices, energy conversion, and smart infrastructure applications. This review discusses the evolution of lead-free ceramics, the challenges in improving polymer-ceramic interfaces, and innovations like 3D printing and surface functionalization, which enhance charge transfer and material durability. It also covers the effects of radiation on these materials, particularly in nuclear applications, and strategies to enhance radiation resistance. The review concludes that polymer materials play a critical role in advancing piezoelectric composite technologies by addressing environmental and functional challenges, paving the way for future innovations.

Flexible Piezoelectric Nanocolumnar Composite Films as Flat-Panel Loudspeakers: Application and Modeling

Highly anisotropic piezoelectric composites promise to progress electroacoustic devices as a class by combining the advantages of both piezoceramics and polymers. Fundamentally, piezoelectric loudspeakers employ the converse piezoelectric effect to convert electrical to mechanical energy. Quasi-1-3 piezoceramic/polymer composites enable flat-panel loudspeakers that are tunable in elastic modulus, with opportunities for mechanical flexibility, optical transparency, and large-area coverage. Their processing route enables relatively flexible design parameters, such as the particle loading, polymer-matrix modulus, film thickness, film size, and electrode-material stiffness. Alternative processing routes of electric field (E-field) aligned-piezoelectric composites are demonstrated, including using the relaxor ferroelectric lead magnesium niobate-lead titanate (PMN-PT) to enhance the acoustic performance and photocurable resins to accelerate the materials processing. Material properties critical for dielectrophoresis are characterized, and loudspeakers were fabricated based on the optimal processing conditions. Subsequently, electroacoustic characterization explores the effect of loudspeaker size, substrate stiffness, the microphone distance, the piezoceramic material, and the matrix modulus. Finally, finite-element (FE) modeling of the electromechanical behavior validates the natural frequencies and modes shapes of the loudspeakers via the analytical solution and frequency response to electrical and mechanical excitation. Good correspondence between the predicted electroacoustic performance and experimentally validated model is observed.

Advanced Materials for Energy Harvesting and Soft Robotics: Emerging Frontiers to Enhance Piezoelectric Performance and Functionality

Piezoelectric energy harvesting captures mechanical energy from a number of sources, such as vibrations, the movement of objects and bodies, impact events, and fluid flow to generate electric power. Such power can be employed to support wireless communication, electronic components, ocean monitoring, tissue engineering, and biomedical devices. A variety of self-powered piezoelectric sensors, transducers, and actuators have been produced for these applications, however approaches to enhance the piezoelectric properties of materials to increase device performance remain a challenging frontier of materials research. In this regard, the intrinsic polarization and properties of materials can be designed or deliberately engineered to enhance the piezo-generated power. This review provides insights into the mechanisms of piezoelectricity in advanced materials, including perovskites, active polymers, and natural biomaterials, with a focus on the chemical and physical strategies employed to enhance the piezo-response and facilitate their integration into complex electronic systems. Applications in energy harvesting and soft robotics are overviewed by highlighting the primary performance figures of merits, the actuation mechanisms, and relevant applications. Key breakthroughs and valuable strategies to further improve both materials and device performance are discussed, together with a critical assessment of the requirements of next-generation piezoelectric systems, and future scientific and technological solutions.

Promising ferroelectric and piezoelectric response of Cr-doped ZnO nanofiller-incorporated PVDF flexible and laminated nanocomposite system

Cr3+-doped ZnO (CZ) nanoparticles are prepared using hydrothermal and co-precipitation techniques. The desired crystallographic phase of the nanoparticles is confirmed using X-ray diffraction study. Rod-shaped and spherical morphologies of CZ nanoparticles prepared using hydrothermal and co-precipitation techniques were confirmed through FESEM observation. Each type of nanoparticle was taken separately in PVDF to understand the characteristic properties, such as dielectric, piezoelectric, and ferroelectric properties of the resultant CZ-PVDF nanocomposite films. All the nanocomposite films comprising rod-shaped or spherical CZ nanoparticles show butterfly loops with a low leakage current density of 10-5 A m-2 at a maximum electric field of 100 kV m-2 under J-E measurement. These findings suggest that the polarization property of CZ-PVDF nanocomposite films can be obtained at a high external electric field without causing electric breakdown in the samples. Dielectric permittivity as a function of temperature increases with an increase in the loading percentage of both rod-shaped or spherical CZ nanofillers in PVDF. Polarization response also improves with an increase in the loading percentage of CZ nanofillers in PVDF. In particular, the rod-shaped CZ nanofillers in PVDF with a higher loading percentage (CZHP2) result in a maximum polarization of (10 ± 0.29) × 10-4 μC cm-2, remanent polarization of (2 ± 0.04) × 10-4 μC cm-2, and coercive field of (10 ± 0.1) kV cm-1 at a maximum electric field of 50 kV cm-1. The CZHP2 nanocomposite film has a piezoelectric coefficient (d33) of (25 ± 0.24) pC N-1 and a power density of 1278.90 W m-3. These results indicate that the nanocomposite films have potential application in piezoelectric energy harvesters, offering a possible solution to the energy issue faced by modern society.

Electroactive Biomaterials Regulate the Electrophysiological Microenvironment to Promote Bone and Cartilage Tissue Regeneration

The incidence of large bone and articular cartilage defects caused by traumatic injury is increasing worldwide; the tissue regeneration process for these injuries is lengthy due to limited self‐healing ability. Endogenous bioelectrical phenomenon has been well recognized to play an important role in bone and cartilage homeostasis and regeneration. Studies have reported that electrical stimulation (ES) can effectively regulate various biological processes and holds promise as an external intervention to enhance the synthesis of the extracellular matrix, thereby accelerating the process of bone and cartilage regeneration. Hence, electroactive biomaterials have been considered a biomimetic approach to ensure functional recovery by integrating various physiological signals, including electrical, biochemical, and mechanical signals. This review will discuss the role of endogenous bioelectricity in bone and cartilage tissue, as well as the effects of ES on cellular behaviors. Then, recent advances in electroactive materials and their applications in bone and cartilage tissue regeneration are systematically overviewed, with a focus on their advantages and disadvantages as tissue repair materials and performances in the modulation of cell fate. Finally, the significance of mimicking the electrophysiological microenvironment of target tissue is emphasized and future development challenges of electroactive biomaterials for bone and cartilage repair strategies are proposed.

Significantly Enhanced Poling Efficiency of Piezocomposites by Tuning Resistivity of a Polymer Matrix

Although the ability to convert biomechanical vibrations into electric energy has been demonstrated in organic-inorganic piezocomposites, it is challenging to improve their piezoelectric properties owing to insufficient electric field poling. Here, we propose a facile and effective approach to enhance the poling efficiency of a barium calcium zirconate titanate/polydimethylsiloxane (BCZT/PDMS) composite by introducing copper nanowires (Cu NWs) to tune the resistivity of the PDMS matrix. The Cu NW-modified PDMS weakens the resistivity mismatch between the BCZT filler and the PDMS matrix, allowing a higher poling electric field to be applied to the BCZT filler during poling. As a result, the BCZT/Cu-PDMS piezocomposite exhibited a high piezoelectric quality factor (d33 × g33) of 2.58 pm2/N, which was about 7 times higher than that of BCZT/PDMS (d33 × g33 = 0.38 pm2/N). Moreover, BCZT/Cu-PDMS showed a much higher power density (3.18 μW/cm2) and a faster charging capability. This composite approach of introducing metal nanowires can be considered as a generic poling-improvement method that can be extended to other organic-inorganic piezocomposite systems.