Piezoelectric Ceramic-polymer Composites Research Articles

Enhancing Neural Stem Cell Stimulation with Structured Piezoelectric Composites: An In Vitro Study

Spinal cord injuries can cause permanent tissue damage with debilitating and lasting effects on patients. Electrical stimulation has been established as an effective approach for promoting neural regeneration. However, the clinical applicability of these techniques is limited by the necessity for wired connections and external power supplies, which increases risk of infection. Piezoelectric materials have the inherent ability to form electric surface potentials when subjected to a mechanical stress and can provide wireless electrical stimulation. However, current materials are not optimized for neurological applications as they are mechanically mismatched with neural tissue, and have poor biocompatibility. Further, reproducible systems for optimizing material design and stimulation paradigms have yet to be established. Here a new, advanced fabrication process to produce scalable, tuneable piezoelectric ceramic–polymer composites based on [K0.5Na0.5]NbO3 and polydimethylsiloxane is provided. It is demonstrated that these composites can be successfully utilized for the growth of neural stem cells, which are shown to survive, proliferate, retain stemness, and differentiate into their daughter populations. Neuronal differentiation appears to be preferred on poled substrates, in comparison to glass coverslips and unpoled substrates. It is shown that the composites can autonomously generate surface potentials, which opens new possibilities to study piezoelectrically induced electrical stimulation.

SH-wave scattering by the interface crack of piezoelectric ceramic polymer composites

The scattering of SH waves by interfacial crack in piezoelectric ceramic polymer composites is investigated. The mixed boundary condition are reduced to dual integral equations using Fourier transforms, and the series and Schmidt methods are used to solve an unknown quantity in crack displacement, and the expression of stress intensity factor at crack tip is obtained. The method was verified by degrading the piezoelectric ceramic polymer to the piezoelectric ceramic material. Finally, the crack propagation under different conditions such as frequency and angle are analyzed, as well as the influence of different piezoelectric ceramic polymer materials on crack propagation. It is of great significance for fracture propagation. This method can also be used as a guide for SH wave scattering of different interface cracks in real life, such as multi-cracks, rectangular crack and penny-shaped crack, so it can also be used as a starting point for future research.

Improving the performance of flexible composites based on 3-3 interconnected skeletons for piezoelectric energy harvesting

With the rapid development of microelectronics and portable devices, flexible piezoelectric electricity generators (FPEGs) as self-powered devices have attracted extensive attention. Piezoelectric ceramic-polymer composites with good flexibility is the core component of FPEGs. Having high d33 and g33 values is also essential for power generation. Herein, the porous ceramic skeleton is prepared using PZT based as the ceramic powder and polyurethane sponge as the template, followed by compounding the porous ceramic skeleton with polydimethylsiloxane (PDMS) by vacuum impregnation to prepare a 3-3 interconnected composite. When the ratio of ceramic phase in the ceramic slurry is 75 wt%, the volume fraction of the ceramic phase in the composite can achieve 37 vol%. Before compounding PDMS, porous ceramics are polarised, which is called pre-polarisation. The d33 value of the pre-polarised composites can reach 158 pC/N as compared to not polarising the porous ceramic and then polarising it after composite; the improvement is 48%. In addition, the g33 value of the pre-polarized composites is up to 144 mV m/N. Moreover, the 3.0 × 1.2 × 0.2 cm3 FPEG can generate a maximum output voltage of 15 V and a maximum short circuit current of 167 nA at 9% compression strain. The maximum instantaneous power density is 990 nW/cm2, thereby providing a new idea for piezoelectric power generation.

Piezoelectric properties of triply periodic minimum surface structures

Piezoelectric ceramic-polymer composites have attracted substantial interest owing to their distinct piezoelectric performance. This paper investigates the dependence of their output voltage on the volume fraction and structure of the ceramic component, together with the type of stimulus, using finite element analysis. When ceramic parts of piezocomposites are shaped into structures with a topology of triply periodic minimum surface such as Schwarz Primitive surface, Gyroid surface, and Neovius surface, they exhibit much better piezoelectric performance than existing piezocomposites under both the compressive strain and the shear strain. Compared to a piezocomposite with three intersecting ceramic cuboids, Schwarz piezocomposite with the same volume fraction of 50% can increase output voltage by approximately 50% under compressive strains 2%–8%. With 16% ceramic material and under a compressive strain of 8%, Neovius piezocomposite demonstrates ~17-fold and ~6,000-fold enhancement of output voltage than that of the piezocomposite in the 3-3 mode (connected and irregularly-shaped ceramic component) and in the 0–3 mode (disconnected ceramic particles), respectively. Under simple shear, performance superiority of Neovius piezocomposite to that of the 3-3 mode piezocomposite becomes more significant as output voltage can be enhanced up to approximately 30-fold. Computational analysis shows that high von Mises stress helps to enlarge the difference between positive and negative electrical potential, and therefore enhance output voltage. The findings in this work also reveal output voltage is inversely proportional to strain energy stored in piezocomposites. Because Schwarz piezocomposite has the largest bulk modulus with minimum strain energy under compression, it has the maximum output voltage.

Effect of Polymer-Ceramic Fibre Interphase Design on Coupling Factor in Low Fibre Volume Content Piezoelectric Composites

In this work, we investigated different short molecule polymer coatings in piezoelectric ceramic-polymer composites with low fibre volume contents. Modifying the interphase between the piezoelectric PZT (lead zirconate titanate) fibre and the epoxy matrix thus enhances the electromechanical coupling factor for 1–3 ultrasound transducers with low fibre contents. It is known that the electromechanical coupling factor can be increased by precoating a ceramic fibre with a soft interlayer polymer [1-1-3]. In this paper, we investigate the so-called 1-1-1-3 composites composed of a ferroelectric ceramic fibre (core), a soft polymer layer (e.g., fatty acids, amides, waxes, or oils), an epoxy resin shell, and an epoxy resin matrix. Some soft polymer layers allowed the free movement of the ferroelectric fibres reducing blocking or clamping by the inactive polymeric matrix, resulting in higher electromechanical coupling factors (kt) for composites with low fibre volume contents. Using an oil-based interlayer, the dielectric constant can be significantly increased. The lowest fibre push-out stress could be achieved with the paraffin interlayer; however, no correlation with the coupling factor could be observed.

Piezoelectric Flexible LCP–PZT Composites for Sensor Applications at Elevated Temperatures

In this paper fabrication of piezoelectric ceramic–polymer composites is demonstrated via filament extrusion enabling cost-efficient large-scale production of highly bendable pressure sensors feasible for elevated temperatures. These composites are fabricated by utilizing environmentally resistant and stable liquid crystal polymer matrix with addition of lead zirconate titanate at loading levels of 30 vol%. These composites, of approximately 0.99 mm thick and length of > 50 cm, achieved excellent bendability with minimum bending radius of ~ 6.6 cm. The maximum piezoelectric coefficients d33 and g33 of the composites were > 14 pC/N and > 108 mVm/N at pressure < 10 kPa. In all cases, the piezoelectric charge coefficient (d33) of the composites decreased as a function of pressure. Also, piezoelectric coefficient (d33) further decreased in the case of increased frequency press-release cycle sand pre-stress levels by approximately 37–50%. However, the obtained results provide tools for fabricating novel piezoelectric sensors in highly efficient way for environments with elevated temperatures.

Piezoelectric Ceramic-Polymer Composites as Smart Materials: An Overview of Preparation Methods

Piezoelectric Ceramic-Polymer Composites as Smart Materials: An Overview of Preparation Methods

Effect of Phase Change in Piezoelectric Ceramic-Polymer Composites and their Applications

Effect of Phase Change in Piezoelectric Ceramic-Polymer Composites and their Applications

Fabrication and Characterization of the Piezoelectric Ceramic–Polymer Composites

The modified sol–gel method was used to synthesize lead zirconate titanate nanoparticles, and the lead zirconate titanate nanoparticles and polyvinylidene fluoride were used to prepare piezoelectric nano‐ceramic–polymer composites with 0–3 connectivity type. The composites were successfully prepared by cold‐pressing and curing‐molding methods. X‐ray diffraction and scanning electron microscopy were adopted to characterize the microstructure of the obtained lead zirconate titanate nanoparticles and composites. The normal vibration modes of the lead zirconate titanate nanoparticles were investigated by Fourier transform infrared spectroscopy. The dielectric and piezoelectric properties of the composites were analyzed in detail with respect to different volume fractions of the lead zirconate titanate nanoparticles. It demonstrated that the values of d33 and ε increased with the increase in the content of lead zirconate titanate. The results here pointed to potential and simple methods to fabricate the lead zirconate titanate nanoparticles and the piezoelectric ceramic–polymer composites for piezoelectric applications.

Temperature-Dependent Properties of a 1–3 Connectivity Piezoelectric Ceramic–Polymer Composite

Abstract In this work, the 1–3 connectivity piezoelectric ceramic–polymer composites have been fabricated by a viscous-polymer processing, where 0.90Pb(Zr0.52Ti0.48)O3–0.05Pb(Mn1/3Sb2/3)O3–0.05Pb(Zn1/3Nb2/3)O3 (PZT–PMS–PZN) fibers with 0.5 volume fraction were aligned in epoxy matrix. The sintered PZT fibers, with average diameter of 300 μm and aspect ratio (height/diameter) higher than 3, all showed a pure perovskite phase structure and highly dense morphology. The dielectric, piezoelectric, ferroelectric properties and the vibration modes of the 1–3 composites were measured and demonstrated in comparison with that of the monolithic piezoelectric ceramics. The results confirmed that the 1–3 composites possessed a low acoustic impedance (Z) of 13 MRayl and a high thickness coupling coefficient (k t) of 0.59, in addition, only single thickness vibration mode with the resonance frequency over 1.5 MHz was observed. With temperature elevation, the properties including dielectric constant εr , k t, the ratio of k t to k p (k t/k p) and the acoustic impedance (Z) increase, while the planar electromechanical coupling coefficient (k p) show opposite temperature dependence. Under test temperature of 100°C, the 1–3 composites still present excellent temperature stability with increased k t/k p ratio up to 3.6. The researches on temperature-dependent properties of the 1–3 composites are critical for improving its applications in various environments.

Direct ink writing of 3–3 piezoelectric composite

Three dimensional (3D) ceramic structures form a construction of piezoelectric composite would be prepared with direct ink writing method (DIW). The preparation of aqueous based lead zirconate titanate lanthanum (PLZT) inks and the principle of DIW were systematically investigated. The ink with solids volume fraction about 70vol% by aging 48h reveals shear-thinning behavior and proper viscoelastic properties. As shown by scanning electron microscopy (SEM), PLZT samples sintered at 1200°C for 4h in a lead-rich atmosphere yielded best microstructures which were densified with relative density exceed 98%. The test of X-ray diffraction (XRD) reveals that the main phase of sintered samples is rhombohedral Pb0.93La0.07(Zr0.65Ti0.35)0.9825O3. 3–3 Piezoelectric composite formed by 3D PLZT ceramics filled with epoxy resin at 40°C have higher hydrostatic figure of merit dhgh (4112×10−15m2/N) than that of the monolithic PLZT piezoelectric ceramics (365×10−15m2/N). Piezoelectric ceramic–polymer composites can be widely used for the applications like underwater acoustic transducers in having combined hardness and electric properties of piezoelectric ceramics and flexibility, low density and low acoustic impedance of polymers.

Piezoelectric and mechanical properties of fatigue resistant, self-healing PZT–ionomer composites

Piezoelectric ceramic–polymer composites with 0–3 connectivity were fabricated using lead zirconium titanate (PZT) powder dispersed in an ionomer (Zn ionomer) and its reference ethylene methacrylic acid copolymer (EMAA) polymer matrix. The PZT–Zn ionomer and PZT–EMAA composites were prepared by melt extrusion followed by hot pressing. The effects of poling conditions such as temperature, time and electric field on the piezoelectric properties of the composites were investigated. The experimentally observed piezoelectric charge coefficient and dielectric constant of the composites were compared with theoretical models. The results show that PZT–Zn ionomer composites have better piezoelectric properties compared to PZT–EMAA composites. The static and fatigue properties of the composites were investigated. The PZT–Zn ionomer composites were found to have excellent fatigue resistance even at strain levels of 4%. Due to the self-healing capabilities of the ionomer matrix, the loss of piezoelectric properties after high strain tensile cyclic loading could be partially recovered by thermal healing.

Application of gel-casting to the fabrication of 1–3 piezoelectric ceramic–polymer composites for high-frequency ultrasound devices

A modified gel-casting technique was used to fabricate a 1–3 piezoelectric ceramic/polymer composite substrate formed by irregular-shaped pillar arrays of small dimensions and kerfs. This technique involves the polymerization of aqueous piezoelectric (PZT) suspensions with added water-soluble epoxy resin and polyamine-based hardener that lead to high strength, high density and resilient ceramic bodies. Soft micromoulding was used to shape the ceramic segments, and micropillars with lateral features down to 4 µm and height-to-width aspect ratios of ∼10 were achieved. The composite exhibited a clear thickness resonance mode at approximately 70 MHz and a keff ∼ 0.51, demonstrating that the ceramic micropillars possess good electrical properties. Furthermore, gel-casting allows the fabrication of ceramic structures with non-conventional shapes; hence, device design is not limited by the standard fabrication methods. This is of particular benefit for high-frequency transducers where the critical design dimensions are reduced.

Dielectric and piezoelectric properties of ceramic-polymer composites with 0–3 connectivity type

Piezoelectric ceramic-polymer composites with 0–3 connectivity were fabricated from lead zirconate titanate (PZT) and poly(vinylidene-fluoride-chlorotrifluoroethylene [P(VDF-CTFE)] copolymer. PZT-P(VDF-CTFE) composites were prepared using the hot press method under various pressure levels of P(VDF-CTFE) at 170°C. The composites were investigated for density, as well as their dielectric and piezoelectric properties, while the particle size of the PZT powder and volume fraction were varied. The connectivity model for the composites was evaluated on the basis of the measured dielectric properties. The piezoelectric voltage constant (g 33 ) was found to achieve a maximum value with a volume fraction of 60 %. In addition, the PZT-P(VDF-CTFE) composite with a 60 % volume fraction was found to yield optimum d 33 × g 33 value of 7.27 pm2/N.

Direct strain energy harvesting in automobile tires using piezoelectric PZT–polymer composites

Direct piezoelectric strain energy harvesting can be used to power wireless autonomous sensors in environments where low frequency, high strains are present, such as in automobile tires during operation. However, these high strains place stringent demands on the materials with respect to mechanical failure or depolarization, especially at elevated temperatures. In this work, three kinds of ceramic–polymer composite piezoelectric materials were evaluated and compared against state-of-the-art piezoelectric materials. The new composites are unstructured and structured composites containing granular lead zirconate titanate (PZT) particles or PZT fibers in a polyurethane matrix. The composites were used to build energy harvesting patches which were attached to a tire and tested under simulated rolling conditions. The energy density of the piezoelectric ceramic–polymer composite materials is initially not as high as that of the reference materials (a macro-fiber composite and a polyvinylidene fluoride polymer). However, the area normalized power output of the composites after temperature and strain cycling is comparable to that of the reference devices because the piezoelectric ceramic–polymer composites did not degrade during operation.

Rapid Prototyping of Novel Piezoelectric Composites

Piezoelectric ceramic-polymer composites have been conceptualized, prototyped, fabricated by rapid prototyping in order to surpass those fabricated with traditional processing methods in novelty as well as performance. Rapid prototyping offers unmatched design and fabrication flexibility in achieving structural complexity and hierarchy in developing piezoelectric composites. A detailed account of all salient aspects of Fused Deposition of Ceramics (FDC) and Fused Deposition of Multi-Materials (FDMM), two major technologies pioneered at Rutgers University, are discussed. Structure-processing-property relations are elaborated on using connectivity as the unifying central concept. Examples of novel piezoelectric ceramic-polymer composites fabricated using FDC and FDMM are given, and pertinent electromechanical properties are discussed. Pending challenges in this line of research are also elaborated on.

Piezoelectric composites for sensor and actuator applications

In the last 25 years, piezoelectric ceramic-polymer composites have been conceptualized, prototyped, fabricated, and implemented in an array of applications encompassing medical imaging and military missions, among others. A detailed snapshot of the materials used, and a detailed account of the major innovative methods developed in making various piezoelectric ceramic-polymer composites are presented. The salient aspects of processing of such composites are summarized, and structure-processing-property relations are described using connectivity as the unifying central concept. Computer-aided design (CAD)-based fabrication methods, which result in composites whose structural complexity surpass that of composites obtained with traditional methods, are described to introduce the reader to novel concepts in processing of piezocomposites. A brief survey of some recent advances made in modeling of (0-3), (1-3), and (2-2) composites also is provided.

Piezoelectric paint: Ceramic-polymer composites for vibration sensors

A piezoelectric ceramic-polymer composite has been developed for use as a novel thick film strain sensor for vibration monitoring of structures. The material is in the form of a paint that can be applied to a wide range of substrates using conventional spraying equipment. The sensor properties depend on the morphology of the composite and on the electrodes that are used to couple it to the charge amplifier. Electrodes of various kinds have been tested. Interaction between the electrode and the piezoelectric paint sometimes occurs (for example, the organic vehicle for spray-coated electrodes may interact with the paint binder). The morphologies of the piezoelectric paint and of the electrode materials have been studied using light optical microscopy and scanning electron microscopy to investigate the effect of different compositions and of different processing conditions (e.g., paint mixing schedule). Preliminary work is reported on the characteristics of the piezoelectric particles and on the effect of heat treatment applied to anneal out defects produced by milling. X-ray analysis and particle size analysis have been used to characterize the changes that take place on heat treatment. X-ray diffractometry has also been used to follow the effect of poling on the paint sensors. At the present state of development, sensors made using the paint have a dynamic range of at least 40–4000 microstrain and a bandwidth of at least 1 Hz–2 kHz, and piezoelectric coefficient d31 of approximately 20 pC/N. The sensors are resistant to outdoor exposure and a successful field trial has been conducted.

The Horizontally Polarized Shear Waves in Multilayered Piezo-Composites with 2-2 Connectivity

Following the advances in structural applications, composite structures are being used commonly in transducer applications to improve acoustic, mechanical and electrical performance of piezoelectric devices. Functional composite transducers for sensors and actuators generally consist of ceramics and polymers, the disadvantage of the brittleness nature of the piezoelectric ceramics can be overcome and the structures especially good for sensing can be allowed for building up. Propagation behavior of horizontally polarized shear waves (SH-waves) in piezoelectric ceramic-polymer composites with 2-2 connectivity is taken into account. The multilayer structures are consisted of piezoelectric thin films bonded perfectly with polymeric thin films alternately. The phase velocity equations of SH-waves propagation in the piezoelectric ceramic-polymer composites with 2-2 connectivity are obtained for the cases of wave propagation in the direction perpendicular to the layering and along the layering, respectively. Filter effect of this kind of structure and the effect of volume fraction and shear modulus ratio of piezoelectric layer to polymer layer on the phase velocity are discussed in detail, respectively. One practical combination of piezoelectric thin film-polymer thin film multilayer system is chosen to carry out the numerical simulation, some basic properties of SH-waves propagation in above multilayered structures are revealed.

Gelcasting based solid freeform fabrication of piezoelectric ceramic objects

Selective laser sintering (SLS) in combination with gelcasting are developed to form complex-shaped lead zirconate titanate (PZT) ceramic frameworks for piezoelectric ceramic polymer composites. SLS is utilized to fabricate lost molds for the ceramic parts. Based on the gelcasting technique and specially selected composite plastic powders for SLS, complex-shaped PZT parts are successfully fabricated.