Piezoelectric Nanorods Research Articles

Analytical modeling and simulations of a piezoelectric nanorod for energy harvesting via Eringen’s differential model

Analytical modeling and simulations of a piezoelectric nanorod for energy harvesting via Eringen’s differential model

Non-Centrosymmetric Single Crystalline Biomolecular Nano-Arrays for Responsive Electronics.

Herein, a novel strategy is reported for synthesizing libraries of single crystalline amino acid (AA) nanocrystals with control over size, anisotropy, and polymorphism by leveraging dip-pen nanolithography (DPN) and recrystallization via solvent vapor annealing. The crystals are prepared by first depositing nanoreactors consisting of a solvent with AAs, followed by water vapor-induced recrystallization. This leads to isotropic structures that are non-centrosymmetric with strong piezoelectric (g33 coefficients >1000mVmN-1), ferroelectric, and non-linear optical properties. However, recrystallizing arrays of isotropic DL-alanine nanodot features with a binary solvent (water and ethanol) leads to arrays of 1D piezoelectric nanorods with their long axis coincident with the polar axis. Moreover, positioning nanoreactors containing AAs (the nanodot features) between micro electrodes leads to capillary formation, making the reactors anisotropic and facilitating piezoelectric nanorod formation between the electrodes. This offers a facile route to device fabrication. These as-fabricated devices respond to ultrasonic stimulation in the form of a piezoelectric response. The technique described herein is significant as it provides a rapid way of investigating non-centrosymmetric nanoscale biocrystals, potentially pivotal for fabricating a new class of stimuli-responsive devices such as sensors, energy harvesters, and stimulators.

Engineering Heterostructured Piezoelectric Nanorods with Rich Oxygen Vacancy‐Mediated Piezoelectricity for Ultrasound‐Triggered Piezocatalytic Cancer Therapy

AbstractUsing piezoelectric bionanomaterials to promote the generation of reactive oxygen species (ROS) is being increasingly recognized in ultrasound (US)‐triggered tumor treatments. The mechanism underlying this innovative treatment involves US irradiation, which activates the built‐in electric field (BIEF) and induces energy‐band bending in piezoelectric materials (PEMs). In this study, Sr0.5Ba0.5Nb2O6 (SBN) nanorods (NRs) are synthesized using a molten salt method. Subsequently, oxygen‐vacancy (OV)‐rich SBN/Sr2Nb2O7 (SBN/SNO) heterojunction nanocomposites (NCs) are fabricated via H2 annealing of the SBN NRs. The engineering strategy focused on enhancing ROS generation, thereby augmenting the piezoelectric catalytic activity of the NCs. This configuration ensures that the BIEF and heterojunction‐induced field act synergistically to provide a sustained driving force for the separation of electron‐hole (e−‐h+) pairs. Importantly, the OVs on the surfaces of the H2‐annealed SBN NRs create electron‐rich sites, which substantially enhance their piezocatalytic capabilities. In vitro and in vivo analyses of hepatocellular carcinoma (HCC) models demonstrate the significant cytotoxic and tumor‐inhibitory capabilities of this rich OV‐mediated sonopiezoelectric therapy (SPT) and illustrate its potential as a promising therapeutic approach against cancer.

A new constitutive theory of nonlocal piezoelectric thermoelasticity based on nonlocal single-phase lag heat conduction and structural transient thermo-electromechanical response of piezoelectric nanorod

Thermo-electromechanical coupling analysis at micro and nano temporal and spatial scales becomes significantly important with extensive application of ultrafast heating technology to micro/nano-machining and manufacturing of piezoelectric micro/nano-devices, where the size effects in heat conduction and elastic deformation remarkably increase. This article aims to establish a new nonlocal piezoelectric thermoelasticity theory based on newly developed model of Eringen-type nonlocal single-phase-lag heat conduction via Eringen’s nonlocal continuum mechanics. The proposed model is applied to analyze the thermo-electromechanical responses of piezoelectric nanorod by Laplace transformation technique. The effects of nonlocal characteristic lengths on wave propagations and structural transient response are evaluated and discussed.

Investigation of the vibration behavior of nano piezoelectric rod using surface effects and non-local elasticity theory

Due to the importance of the analysis of piezoelectric nanorods and the different conditions they are exposed to in engineering problems, in this research, for the first time, both nonlocal elasticity theory and surface energy theory have been used simultaneously to model a piezoelectric nanorod. The natural frequency values of the system have been extracted using the Galerkin weighted residual method. By applying an external excitation voltage, the forced vibrations of nonlocal nanorods with surface effects are presented. The results are reported for different vibrational modes, and the impact of different parameters such as dimensions, nonlocal parameters, and surface effects are investigated. The results of this study prove that the nonlocal elastic theory is more effective than the surface energy theory on the vibration behavior of piezoelectric nanorods. Also, the effect of piezoelectric properties is strengthened due to the nanoscale of the rods.

Mixed Dimensional ZnO/WSe2 Piezo-gated Transistor with Active Millinewton Force Sensing.

This work demonstrates a mixed-dimensional piezoelectric-gated transistor in the microscale that could be used as a millinewton force sensor. The force-sensing transistor consists of 1D piezoelectric zinc oxide (ZnO) nanorods (NRs) as the gate control and multilayer tungsten diselenide (WSe2) as the transistor channel. The applied mechanical force on piezoelectric NRs can induce a drain-source current change (ΔIds) on the WSe2 channel. The different doping types of the WSe2 channel have been found to lead to different directions of ΔIds. The pressure from the calibration weight of 5 g has been observed to result in an ∼30% Ids change for ZnO NRs on the p-type doped WSe2 device and an ∼-10% Ids change for the device with an n-type doped WSe2. The outcome of this work would be useful for applications in future human-machine interfaces and smart biomedical tools.

Axial Free Vibration of Rotating FG Piezoelectric Nano-rods Accounting for Nonlocal and Strain Gradient Effects

Axial Free Vibration of Rotating FG Piezoelectric Nano-rods Accounting for Nonlocal and Strain Gradient Effects

Ultrahigh piezoelectric coefficients of Li-doped (K,Na)NbO3 nanorod arrays with manipulated O-T phase boundary: Towards energy harvesting and self-powered human movement monitoring

Lead-free piezoelectric one-dimensional (1D) nanostructures have exhibited great potential in building biocompatible micro/nano-energy harvesters and self-powered smart sensors. However, their low piezoelectric coefficient still remains as the biggest obstacle for practical applications. In this work, an ultrahigh piezoelectric coefficient with calibrated d 33 from 400 pm V -1 to 814 pm V -1 is achieved in Li-doped (K,Na)NbO 3 (KNLN) lead-free piezoelectric nanorod arrays (NRAs). The giant enhancement on the piezoelectric performance of the KNLN nanorods can be attributed to the manipulation on the phase transition behavior together with the relaxation of strain. The Li + dopants induce large NbO 6 octahedral distortion and result in the decreased phase transition temperature from orthorhombic (O) to tetragonal (T) phase, which leads to the construction of the O-T phase boundary at room temperature and improves the polarization performance of the products. The ultrahigh piezoelectric performance of the KNLN NRAs gives rise to the remarkably improved energy harvesting performance, which shows highly sensitive pressure sensing behaviors and can be utilized for monitoring the human-body motions. Giant piezoelectric coefficient d 33 up to 814 pm V -1 is achieved in lead-free (K,Na,Li)NbO 3 nanorod arrays by manipulating the orthorhombic-tetragonal phase boundary through A-site Li-doping. The KNLN nanorod arrays exhibit outstanding piezoelectric energy harvesting and pressure sensing performances and realize the self-powered monitoring of human body motions for smart analyzing of the human movement behaviors. • Li-doped (K,Na)NbO 3 nanorod arrays were grown by hydrothermal process. • Giant piezoelectric coefficient d 33 ~ 814 pm V − 1 is achieved in KNLN nanorod arrays. • Orthorhombic-tetragonal phase boundary of KNLN nanorods is constructed at RT. • The nanogenerators exhibit outstanding energy harvesting and sensing performance. • Self-powered human-body-movements monitoring is realized by KNLN nanogenerators.

Simultaneous acquisition of current and lateral force signals during AFM for characterising the piezoelectric and triboelectric effects of ZnO nanorods

Atomic force microscopy (AFM) is central to investigating the piezoelectric potentials of one-dimensional nanomaterials. The AFM probe is used to deflect individual piezoelectric nanorods and to measure the resultant current. However, the torsion data of AFM probes have not been exploited to elucidate the relationship between the applied mechanical force and resultant current. In this study, the effect of the size of ZnO nanorods on the efficiency of conversion of the applied mechanical force into current was investigated by simultaneously acquiring the conductive AFM and lateral force microscopy signals. The conversion efficiency was calculated based on linear regression analysis of the scatter plot of the data. This method is suitable for determining the conversion efficiencies of all types of freestanding piezoelectric nanomaterials grown under different conditions. A pixel-wise comparison of the current and lateral force images elucidated the mechanism of current generation from dense arrays of ZnO nanorods. The current signals generated from the ZnO nanorods by the AFM probe originated from the piezoelectric and triboelectric effects. The current signals contributed by the triboelectric effect were alleviated by using an AFM probe with a smaller spring constant and reducing the normal force.

Triboelectric-piezoelectric hybrid nanogenerator based on BaTiO3-Nanorods/Chitosan enhanced output performance with self-charge-pumping system

Recent advances in achieving flexible triboelectric nanogenerators (TENGs) focus widely on utilizing and modifying abundant natural biopolymer. Boosting power generation and conversion efficiency continue to prevail. In this work, three main strategies were proposed to enhance the output performance of chitosan-based TENGs; 1) hybridization with lead-free piezoelectric nanorod, 2) introduction of a soft electrode using bacterial cellulose/carbon nanotube composite to enhance contact efficiency, and 3) enhancement of charge density of the triboelectric friction layer using a self-charge pumping (SCP) module. Under the same testing conditions of 48 ± 5% relative humidity, ~0.55 Hz of frequency, ~250 N of compressive force at 25.0 ± 0.5 °C, and the combination of 7 wt% lead-free piezoelectric BaTiO3 nanorods (BT-NRs) in the chitosan matrix, the highest open-circuit voltage (Voc) of ~111.4 V, short circuit (Isc) of ~21.6 μA/cm2, and also output power density of 756 μW/cm2 was achieved. By using an integrated SCP module, the TENGs can provide a Voc, Isc and peak power output of 247.2 V, 36.7 μA/cm2 and 1568 μW/cm2, respectively. This electrical power output rises to over 4-fold more power enhancement than that of pristine chitosan TENGs. The TENGs demonstrate remarkable mechanical stability and reliability upon cyclical contact for up to 3000 times. This work provides a promising strategy for achieving high-output, eco-friendly triboelectric nanogenerators. By boosting the output performance via continuous charge pumping, ultrahigh effective charge density was achieved successfully in flexible chitosan/BT-NR biocomposites that can push output performance towards real applications of TENGs.

FUZZY SIMULATION, SYNTHESIS, CHARACTERIZATION AND VOLTAGE MEASUREMENTS OF ZINC OXIDE NANO-RODS BASED NANOGENERATORS

Harvesting the mechanical energy from environment sources such as wavy motion of plant leaves and branches could power up the low power consumption electrical devices and sensors. Such low power energy harvesting devices will replace the batteries especially at the remote areas where the replacement of batteries is very expensive or sometimes impossible. An environment friendly nano generator using ZnO nanorods can be built easily and useful for energy generation. Although, performance of harvesting ZnO piezoelectric nanorods have gradually improved even then their power is insufficient for real devices. However, the integration of nanogenerator devices for energy harvesting into a single power source is necessary. Therefore, its simulation using MATLAB fuzzy logic and fabrication is presented in this paper with a very low error of 0.24 % which shows its excellence in performance by presenting new technique of energy generation with plant leave movement. The fabricated ZnO nano-wires on aluminum substrate connected in series and parallel were also tested and the results are closely in contrast to the stimulated results. The nano-generator shows an enhanced voltage when connected in series and a high current value when connected in parallel. The nano-generator give a voltage of 0.695 mV when connected in series and a current density of 25 nA cm-2when connected in parallel.

Efficient coupling of lateral force in GaN nanorod piezoelectric nanogenerators by vertically integrated pyramided Si substrate

Piezoelectric energy harvesting is a promising technique for scavenging ambient mechanical motion for driving compact, low-power, multi-functional electronic devices. To adapt to various ambient surroundings, the geometric configurations and sizes varied in wide ranges with high operational reliabilities and piezoelectric performance have been regarded as a key for piezoelectric harvester design. Herein, by applying a normal force, we report an innovative structure for harvesting electric energy from bending the obliquely aligned GaN piezoelectric nanorods (NRs) that are integrated in the vertically integrated nanogenerator (VING). The single-crystalline GaN NRs used here were successfully synthesized with obliquely alignments on the pyramided Si substrate by plasma-assisted molecular beam epitaxy (PA-MBE). Using conductive atomic force microscope (c-AFM), a remarkable change in the Schottky barrier height (SBH) between the tip and GaN NR is observed upon bending an oblique-aligned GaN NR. This demonstrates that a remarkably enhanced piezoelectric performance of GaN NRs can be achieved by coupling a lateral force. We anticipate that this work will provide an efficient approach for coupling the lateral loading to enhance the electric potential in piezoelectric NRs-embedded VING, and thus open a new path for efficiently generating electric energy.

Employing the coupled stress components and surface elasticity for nonlocal solution of wave propagation of a functionally graded piezoelectric Love nanorod model

The higher-order stress components and surface effect are considered in this article for presentation of a nonlocal solution for a functionally graded piezoelectric nanorod. Love rod model is used for longitudinal wave propagation. The mentioned analysis is used to evaluate the governing differential equations of the system and characteristics of wave propagation in assumed nanorod. The model is excited by a two-dimensional electric potential and an initial applied voltage at top layer of rod. The mechanical and electrical properties are assumed variable along the thickness direction of rod. Hamilton’s principle is used to arrive to governing differential equations of the electromechanical system. The effect of some important parameters such as applied voltage and gradation of material properties is studied on the wave characteristics of the rod. Furthermore, the effect of different distributions of electric potential on the phase velocity of the nanorod is evaluated.

Surface effect and non-local elasticity in wave propagation of functionally graded piezoelectric nano-rod excited to applied voltage

A non-local solution for a functionally graded piezoelectric nano-rod is presented by accounting the surface effect. This solution is used to evaluate the characteristics of the wave propagation in the rod structure. The model is loaded under a two-dimensional (2D) electric potential and an initially applied voltage at the top of the rod. The mechanical and electrical properties are assumed to be variable along the thickness direction of the rod according to the power law. The Hamilton principle is used to derive the governing differential equations of the electromechanical system. The effects of some important parameters such as the applied voltage and gradation of the material properties on the wave characteristics of the rod are studied.

Ultrasonic sensing device with ZnO piezoelectric nanorods by selectively electrospraying method

In this study, electrospraying method and hydrothermal process were utilized to fabricate the piezoelectric zinc oxide (ZnO) nanorods. The optimum growing parameters were studied. The electric field around 533–800V/mm was determined to electrospray ZnO seed layer selectively on Au/chromium/silicon substrates. And the coverage rate of the ZnO seed layers can be controlled. Piezoelectric ZnO nanorods with height of 3–5μm (aspect ratio from 10 to 16) were obtained. The ZnO nanorods were packaged in arrays of 1×1, 2×2, 3×3, 4×4 and 5×5 to characterize their piezoelectric properties. We used X-ray diffraction (XRD), photoluminescence (PL) and field emission scanning electron microscopy (FE-SEM) to analyze the morphology and luminescence of ZnO nanorods. For the sensing test, the lower electrode is platinum (Pt) deposited by sputtering that forms Schottky contact with ZnO nanorods, and the upper one is Au. Then they were packaged to measure the underwater ultrasonic waves. With the signals provided by ultrasonic probe, the relation between average voltage output and the force output can be obtained as a function of the various frequencies and distances.

Structure and composition characterization of lead-free (K, Na)NbO3 piezoelectric nanorods synthesized by the molten-salt reaction

Composition-controlled (K, Na)NbO3 piezoelectric nanorods were synthesized, and the chemical homogeneity and Raman frequency dependence on alkaline contents were investigated.

Synthesis of highly piezoelectric lead-free (K, Na)NbO3 one-dimensional perovskite nanostructures

High-aspect-ratio single-crystalline KNN nanorods (length ~10-20 μm and diameter ~400 nm) are synthesized using a facile method based on a molten-salt reaction, whose formation mechanism has been revealed. The lead-free piezoelectric nanorods showing high piezoelectric coefficient d*33 up to ~230 pm V(-1) may be used in bio-sensing and energy-harvesting micro-devices.

ZnO nanorods for energy generation and harvesting

Hydrothermal methods have been used for synthesising one-dimensional ZnO nanorods. These nanorods are found to be highly piezoelectric, i.e., they generate a potential when subjected to mechanical bending or deformations. Main concerns have been the harvesting of that energy and transferring them to the outside world. This can be achieved by an electrode capable of touching the nanorod tips during the bending process. In this work, we synthesise vertically standing ZnO nanorods at low temperature (below the boiling point of water) using a simple hydrothermal route. Glass substrates rendered conducting by a layer of tin-doped indium oxides were used for growing the piezoelectric nanorods. These nanorods were subjected to bending, such that piezo-potentials were generated on the tips with respect to their bases. A gold-sputtered electrode was placed on top of the nanorod array to touch them softly at the tips. Piezo-potential generated was extracted using this electrode.

A facile method to fabricate vertically aligned (K,Na)NbO3 lead-free piezoelectric nanorods

This paper reports on a hydrothermal process to grow vertically aligned (K,Na)NbO3 lead-free piezoelectric nanorods on a single crystal SrTiO3 substrate. Under optimized conditions, micrometer-order-long (K,Na)NbO3 nanorods with a sectional width of about 100 nm were vertically grown on a (100)-cut SrTiO3 wafer with an oriented (K,Na)NbO3 film as a seeding layer, whereas KNN rods were not preferentially grown on bare wafers and no vertical KNN rods were formed on (110)- or (111)-cut substrates even with the (K,Na)NbO3 films. The growth direction of the nanorods was revealed to be along the 〈100〉 direction, which is deduced to contribute to the vertical growth of nanorods on (100)-cut SrTiO3 substrates. The vertical arrays of KNN nanorods may find potential applications in energy harvesting nanodevices and nanoscale 1–3 type multifunctional composites.

Self-Connected and Habitually Tilted Piezoelectric Nanorod Array

We fabricated a self-connected and habitually tilted ZnO nanorod (NR) array, which is free of any patterning process for the connection of the NRs and is easily bent by a normal force. The vertically well-aligned ZnO NRs were grown by a strain relaxation process on MgO-buffered C-plane sapphire, and the remaining epitaxial ZnO wetting layer acted as a self-connecting layer of NRs. The epitaxial ZnO film on the step-terrace structured substrate caused the tilting angle from the surface normal direction (~0.2°) to match the step between the ZnO film and MgO-buffered C-plane sapphire, resulting in easy bending of the ZnO NRs by normal force. The unsymmetrical strain between the tensile and compressive stressed region in the habitually tilted ZnO NRs caused a gradient in the piezoelectric potential, resulting in an electrical field along the lateral direction of NR growth, resulting in the control of the current direction and level to be about 0.1 μA/cm(2) at 2 kgf normal force.