Piezoelectric Composite Materials Research Articles

PDMS–ZnO flexible piezoelectric composites for measurement of muscle activity

Measurement of muscle activity is important for muscle health monitoring, biomechanics studies, developing prosthesis, etc. This article describes a flexible piezoelectric composite material as a sensing element for measuring muscle activity. The developed piezoelectric material is a composite of polydimethylsiloxane and zinc oxide, and exists in monolayer and bilayer configurations. To test the piezoelectric properties in bending mode, a composite patch is attached to a cantilever beam setup. Peak sinusoidal voltage generated from the composite material due to the vibrating cantilever is found to be highest (1.5 V) for bilayer configuration with 30 wt% ZnO. For testing in axial mode, the peak output voltage from the material due to an impulse load is maximum (0.9 V) for the monolayer configuration of the composite with 30 wt% ZnO. The sensor consisting of a bilayer composite patch is wrapped around a specific muscle to measure its activity. The change in output voltage from the sensor is measured for increasing load and is then mapped to the corresponding value of elastic modulus of the muscle measured using a durometer. The sensitivity of the muscle activity measurement for biceps brachii and flexor carpi is found to be 3.826 and 1.245 V MPa−1, respectively.

PIN-PMN-PT Single Crystal 1-3 Composite-based 20 MHz Ultrasound Phased Array.

Based on a modified dice-and-fill technique, a PIN-PMN-PT single crystal 1-3 composite with the kerf of 12 μm and pitch of 50 μm was prepared. The as-made piezoelectric composite material behaved with high piezoelectric constant (d33 = 1500 pC/N), high electromechanical coefficient (kt = 0.81), and low acoustic impedance (16.2 Mrayls). Using lithography and flexible circuit method, a 48-element phased array was successfully fabricated from such a piezoelectric composite. The array element was measured to have a central frequency of 20 MHz and a fractional bandwidth of approximately 77% at −6 dB. Of particular significance was that this PIN-PMN-PT single crystal 1-3 composite-based phased array exhibits a superior insertion loss compared with PMN-PT single crystal and PZT-5H-based 20 MHz phased arrays. The focusing and steering capabilities of the obtained phased array were demonstrated theoretically and experimentally. These promising results indicate that the PIN-PMN-PT single crystal 1-3 composite-based high frequency phased array is a good candidate for ultrasound imaging applications.

Low-temperature adhesion and the application on conductive treatment of curved-surface piezoelectric composite material

Good conductive treatment of curved-surface piezoelectric composites could prevent failure of curved transducers, which are the core devices of many wideband and high-frequency sonar systems. A series of ratio between epoxy resin and curing agent were tested to investigate conductive treatments of curved-surface piezoelectric composites. The curved-surface piezoelectric composite was first prepared. The sample whose epoxy resin to and curing agent ratio was 100:150 showed the largest welding spot strength in many areas, but its homogeneity was not as good as samples with epoxy resin to curing agent ratio of 100:100 or 100:200. With increases in curing agent, the volume resistivities decreased, and the homogeneity became better.

Singularity of Electromechanical Coupling Field in Piezoelectric Composite Junctions

The double singularities including singular stress field and singular electric displacement field, in the tips of piezoelectric composite junctions, are analyzed by the interpolation matrix method (IMM). The double singularity analysis problem of piezoelectric composite junctions is converted into eigenvalue solution problem of ordinary differential equations with variable coefficients under corresponding boundary conditions. In numerical examples, the first couple of singularity orders and the corresponding characteristic angular functions of displacement and electric potential for the electromechanical coupling field are obtained and comparisons are presented to validate the accuracy of the proposed method. The singularity of the electromechanical coupling field at the tip of piezoelectric composite material junctions is closely related to the bonding angle and fiber direction. According to the numerical results, the best scheme can be configured for the combination of dissimilar materials.

Three-Dimensional Multistack-Printed, Self-Powered Flexible Pressure Sensor Arrays: Piezoelectric Composites with Chemically Anchored Heterogeneous Interfaces.

Recently, the development of pressure sensor devices composed of mechanically flexible materials has gained a tremendous attention for emerging wearable electronics applications. Compared with various sensing materials, piezoelectric composite materials provide a characteristic advantage of enabling energy unit-free integration of sensor compartments. In this study, we develop a new chemical method of synthesizing highly functioning piezoelectric composite materials with electrostatically reinforced heterogeneous interfaces to improve the voltage output signal in all-printed sensor arrays. The surfaces of piezoelectric oxide nanoparticles are decorated subsequently with a cationic polyelectrolyte, polyethyleneimine, and a tri-block copolymer, styrene–ethylene/butylene–styrene grafted with maleic anhydride. To elucidate the factors determining the performance of pressure sensor devices, both the electrical properties and piezoelectric characteristics are investigated comprehensively for various compositional composite materials prepared from chemical and physical rubbers. The resulting device exhibits a sensitivity of 0.28 V·kPa–1 with a linear increment of output voltage in a pressure range up to 30 kPa. It is also demonstrated that the all-printed sensor array is fabricated successfully by a multistack-printing process of conductive, insulating, and piezoelectric composite materials in an additive manufacturing fashion.

Development of a structurally similar element of a helicopter blade with an active twist system

A mathematical model is formulated for calculating the stress-strain state (SSS) of piezoelectric layered polymer composite materials (PCM) equipped with a control piezoactuator. The model implements the principle of thermo-piezoelectric analogy, which allows to move from the coupled boundary value problem of electroelasticity to the boundary value problem of thermoelasticity. The mathematical model was tested with a numerical calculation of the mechanical behavior of a sample structurally similar to a rotor blade, equipped with control piezo-actuators and made of equal strength and unidirectional fiberglass.

Preparation and ferroelectric domain structure of micro-scale piezoelectric array fabricated by Mn doped Pb(In<sub>1/2</sub>Nb<sub>1/2</sub>)O<sub>3</sub>-Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>-PbTiO<sub>3 </sub>single crystal

Relaxor ferroelectric single crystal piezoelectric materials have become the core components of new piezoelectric devices such as ultrasonic transducers used in high-end medical ultrasound diagnostic and therapeutic equipment. High-element density array technology and micro-electro-mechanical systems have developed rapidly. For the new generation of 20–80 MHz medical high-frequency ultrasound transducers, the thickness of high-frequency piezoelectric composite material is usually 20–60 μm, and the width of each piezoelectric column is about 5–15 μm. However, the kerf of traditional cutting-and-filling method is too wide, and it is difficult to reduce the size of the array element, which is not conducive to the density of the array element and the demand for higher frequency applications with higher resolution. In this work, a micromechanical fabrication method based on deep reactive ion etching is used to reduce the slit width and increase the array density. We study the fabrication technology of novel and high-performance relaxor ferroelectric single crystal Mn doped Pb(In<sub>1/2</sub>Nb<sub>1/2</sub>)O<sub>3</sub>-Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>-PbTiO<sub>3</sub> (Mn-PIMNT) micro scale piezoelectric array. The influence of the parameters of lithography and deep reactive ion etching on the morphology of piezoelectric array are studied. We obtain the formation mechanisms of different kerfs, different shapes of piezoelectric array element and the relationship among etching rate of Mn-PIMNT single crystal with antenna power, bias power and etching gas ratio. Finally, the size of piezoelectric array element is less than 10 μm, the etching depth is more than 20 μm, the kerf width is less than 5 μm, the angle is controllable, and the maximum is more than 87°. The ferroelectric domain structure and the regulation of electric field effect of micro scale piezoelectric elements are studied by means of piezoelectric force microscope. The variation rules of piezoelectric properties and micro scale are obtained. This method can effectively bypass the shortcomings of the wide kerf and the destruction of the crystal orientation by the traditional cutting-and-filling method. It provides a new preparation technology for the development of high-frequency piezoelectric composites, high-density ultrasonic transducer arrays and new piezoelectric micro mechanical systems. This project presents the guidance and reference for the new micromachining technology of ferroelectric materials, and also lays the foundation for the high-frequency piezoelectric composite and high-frequency ultrasonic transducer.

Flexible piezoelectric pressure sensor based on polydopamine-modified BaTiO3/PVDF composite film for human motion monitoring

Flexible pressure sensors based on piezoelectric materials have been intensively investigated for their wide applications in wearable electronics. However, traditional films based on inorganic/organic composite piezoelectric materials face the bottleneck of defects and cracks or poor dispersion, which hinders the performance of pressure sensors. Herein, polydopamine (PDA) was introduced as a surface modification agent to modify barium titanate (BaTiO3, BTO), which was then blended with poly(vinylidene fluoride) (PVDF) matrix in different ratios to form uniform and homogeneous PDA@BTO/PVDF composites. Afterwards, the flexible piezoelectric pressure sensor was fabricated by a facial solution-casting method. This PDA-modification strategy can improve the dispersion of BTO into PVDF matrix, as well as reduce the interface hole defects and cracks between the two components. As a result, the 17 wt% PDA@BTO/PVDF sensor exhibited a fast response of 61 ms and a remarkable piezoelectric output voltage of 9.3 V, which showed obvious improvement as compared to the pristine PVDF and BTO/PVDF composite counterparts. In addition, as an energy supplier, the sensor could produce a maximum power of 0.122 μW/cm2 even with high load resistance of 70 MΩ. This pressure sensor was sensitive to various human motions, showing great potential in the applications of wearable electronics.

Numerical calculation of the stress-strain state of piezoelectric layered polymer composite materials equipped with a control piezoactuator

A mathematical model is formulated for calculating the stress-strain state (SSS) of piezo-electric layered polymer composite materials (PCM) equipped with a control piezoactuator. The model implements the principle of thermo-piezoelectric analogy, which allows to move from the coupled boundary value problem ofelectroelasticityto the boundary value problem of thermoelasticity. A comparison of the deformation fields for model layered samples from PCM with a different arrangement of piezoactuatorswas carried out. Verification of the developed mathematical models was carried out. The main patterns and mechanisms are revealedfor controlling the geometry of a layered PCM using embedded piezo-actuators.

Numerical Modeling of PZT- Piezoelectric Composites with Passive and Active Polymer Matrix

Piezoelectric composite materials with a polymer matrix are important for underwater acoustic and biomedical imaging applications. The dependence of electromechanical properties of piezoelectric composite on constituent material characteristics and shape of piezoelectric inclusions is a central problem that provides the opportunity to tailor the performance of piezoelectric composites according to design needs. A numerical model has been developed to investigate the electromechanical properties of 1-3 piezoelectric composites with a passive and active polymer matrix. Maxwell Homogenization method is employed to homogenize the solution domain. It is demonstrated that the use of PVDF as an active polymer matrix has a significant influence on piezoelectric charge coefficient d31, hydrostatic coefficient dh, voltage coefficient gh, and hydrophone figure of merit ghdh when compared to the passive Araldite-D polymer matrix. Overall, a 5 to 30% volume fraction of PZT-7A fiber inclusions in an active polymer matrix is the optimum ratio that has a significant effect on piezoelectric properties. The accuracy and effectiveness of homogenized material constants were verified by comparing the derived composite properties with experimental work published elsewhere. These results provide much needed intuitiveness in the development of piezoelectric polymer composite with better performance for transducer applications.

Research on the Actuation Performance of 2D-Orthotropic Piezoelectric Composite Materials Linear Phased Array Transducer.

Ultrasonic linear phased array actuator for electric-acoustic conversion is the key component of the ultrasonic phased array test system. Focusing on the existing deficiency of using phased array ultrasonic testing technology into complex engineering structure, using the 2D orthotropic piezoelectric composite materials (2D-OPCM) into the research of linear phased array actuator can achieve orientable exciting. The single OPCM element and its array actuator was designed and their mechanical properties of focusing were tested by experiment. The experimental results show that 2D-OPCM ultrasound phased array actuator can achieve precise phased array focusing and deflection, which might be of great promising in the nondestructive evaluation engineering application.

Design and experimental study of a piezoelectric energy harvester in automotive spokes

In order to supply power for the wireless sensors in wheels, a piezoelectric energy harvester installed in spokes is proposed in this paper. The piezoelectric cantilever beam is fixed in the spoke, which has higher practicability than the method mentioned in the related research. The periodic excitation is generated by the gravity effect of the free-end mass in the rotation, and the safety limiting structure is designed. A dynamic model was derived through the Euler–Lagrange method and verified by experiments. Based on the numerical simulation of the model, the parameter design of the harvester was carried out in detail for the R16 size rim. In order to verify the performance, an experimental platform was built with piezoelectric composite fiber materials. The influence of the limiters on the steady state and the sweep response was studied, and the energy harvesting effect was further tested by the experiment on the road. The results show that the harvester designed can obtain 82–1003 μW energy at 50–70 km h−1, which provides the possibility of establishing a self-sufficient intelligent wheel system without maintenance.

2-Dimensional rGO introduced PMN-PT and P(VDF-TrFE) flexible films for enhanced piezoelectric energy harvester

Piezoelectric materials have excellent piezoelectric and dielectric properties for versatile device applications. However, they have brittle properties, particularly under mechanical impulse force. As a result, there have been many attempts to improve their brittle properties by mixing in elastic materials. Here, for the first time, reduced graphene oxide (rGO) was introduced to the Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) and poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) polymer composite films, and showed the highest value of piezoelectric and energy density for flexible energy generation applications. rGO has conducting properties with 2-dimensional structure. This rGO can also be prepared through easy processing. 2-dimensional structured rGO serves as a floating electrode in PMN-PT/polymer composite flexible films. Therefore, a floating electrode can attract electrons in piezoelectric composite materials so as to enhance the energy generation properties. By introducing the rGO based floating electrodes into the PMN-PT and P(VDF-TrFE) composite, the generated output energy density was increased from 0.70 mJ/cm3 to 1.2 mJ/cm3. This the generated output energy density was the recorded outstanding value among the flexible composite films.In this paper, the effects of rGO on the properties of PMN-PT/polymer composites will be investigated and discussed.

A Coupling Electromechanical Cell-Based Smoothed Finite Element Method Based on Micromechanics for Dynamic Characteristics of Piezoelectric Composite Materials

Coupling electromechanical cell-based smoothed finite element method (CSFEM) with the asymptotic homogenization method (AHM) is presented to overcome the overstiffness of FEM. This method could accurately simulate the dynamic responses and electromechanical coupling effects of piezoelectric composite material (PCM) structures. Firstly, the efficient performances for active compounds of round cross-section fibers are calculated based on AHM. Secondly, in the CSFEM, electromechanical multi-physic-field FEM is coupled with gradient smoothing technique. CSFEM returns the nearly exact stiffness of continuum structures, which auto discretes the elements in complex areas more readily and thus remarkably reduces the numerical errors. Static and dynamic characteristics of four PCM structures are investigated using CSFEM with AHM. Results are compared with analytical solution and those of FEM, which proves that CSFEM with AHM is more accurate and reliable than the standard FEM when solving problems of complex structures. Additionally, CSFEM could provide results of higher accuracy even using distorted meshes. Therefore, such method is a robust tool for analyzing mechanical properties of PCM structures.

Optimization of Locations and Fiber Orientations of Piezocomposite Actuators on Flexible Wings for Aeroelastic Control

AbstractSmart piezoelectric fiber composite materials have the potential to improve the aerodynamic properties and aeroelastic responses of flexible wings. Aeroelastic control performance significa...

Preparation and Performance Test of Orthotropic Piezoelectric Composite Material Ultrasonic Phased Array Transducer

Preparation and Performance Test of Orthotropic Piezoelectric Composite Material Ultrasonic Phased Array Transducer

Optimization and simulation analysis of structure parameters of OPCM ultrasonic longitudinal wave actuating element

Abstract The force-electric coupling relationship of the mechanical and electrical properties of piezoelectric composites has been the main factor in the research and development of piezoelectric composites in practical application. A novel orthotropic piezoelectric composite material (OPCM) element is studied in this paper. The properties of the piezoelectric phase and the polymer phase and the influence of the geometrical dimensions of the OPCM on the longitudinal wave drive element are analyzed from the perspective of mechanics and electric power, respectively, and the structural design is optimized. This provides a theoretical basis for the development of OPCM and of new longitudinal ultrasonic phased array actuators.

Conductive treatment of piezoelectric composite material by low-temperature adhesion comparing with ion sputtering

The surface conductive treatment is an essential step for piezoelectric composite material being application, but until now there are many issues remain to be solved. A conductive adhesion with low curable temperature, low resistivity and high welding spot adhesion strength was obtained for the conductive treatment of piezoelectric composite material. The welding spot adhesion strength was defined at first time. The conductive and adhesion properties were studied comparing with samples treated by ion sputtering. The conductive adhesive with curing agent of EDA has the lowest resistivity of 1.973 × 10−4 Ω cm and the highest welding spot adhesion strength of 7.93 MPa.

АНАЛИЗ ВЛИЯНИЯ ПОВЕРХНОСТНЫХ НАПРЯЖЕНИЙ НА ЭФФЕКТИВНЫЕ СВОЙСТВА НАНОПОРИСТЫХ ПЬЕЗОКОМПОЗИТОВ

The present paper considers the homogenization problems for mixed piezoelectric composite materials with stochastic distributions of inclusions or pores and with taking into account the mechanical imperfect interphase boundaries. The accepted interface statements correspond to the Gurtin - Murdoch model and give a significant contribution only for nanostructured composites. To determine the effective properties, an integrated approach was used, based on the theory of effective moduli, on the modelling of representative element volumes and on the finite element method. An aggregate of boundary value problems was described, which allow one to find a complete set of effective stiffness moduli, piezomoduli, and dielectric constants for a piezocomposite of arbitrary anisotropy class. The numerical solution of homogenization problems was carried out in the ANSYS finite-element package, which was used both for modelling of representative element volumes and for computation of the effective properties of composite material. The representative volume consisted of a regular cubic array of piezoelectric finite elements with the material properties of the two phases. The contact boundaries between materials of different phases were covered with elastic membrane elements that simulated interface surface stresses. Specific implementation was performed for nanoporous piezoceramic composites, for which both the initial phases and the homogeneous material were materials of the hexagonal symmetry class, and the pores were considered as piezoelectric material with negligibly small stiffness moduli and piezomoduli. For this composite the membrane elements inherited the anisotropy structure of volume elements on their common edges. As an example, the results of calculations of effective moduli for porous ferroelectric soft piezoceramics PZT-5H were presented. It was noted that the surface stresses on the boundaries of the pores can significantly increase the values of the effective stiffness moduli. However, they had a weak influence on the values of the effective piezomoduli and dielectric constants.

High-Performance PZT-Based Stretchable Piezoelectric Nanogenerator

Stretchable piezoelectric nanogenerators are highly desirable for power supply of flexible electronics. Piezoelectric composite material is the most effective strategy to render piezoelectric nanogenerators stretchable. However, the generated output performance is unsatisfactory due to the low piezoelectric phase proportion. Here we demonstrate a high-performance Pb(Zr0.52Ti0.48)O3 (PZT)-based stretchable piezoelectric nanogenerator (HSPG). The proposed HSPG exhibits excellent output performance with a power density of ∼81.25 μW/cm3, dozens of times higher than previously reported results. Mixing technique, instead of conventional stirring technology, is used to incorporate PZT particles into solid silicone rubber. The filler distribution homogeneity in matrix is thus remarkably improved, allowing higher filler composition. The PZT proportion in composite can be increased to 92 wt % with satisfactory stretchability of 30%. On the basis of the excellent electrical and mechanical properties, the proposed HS...