Nanostructured ZnO/BiVO_(4)I-scheme heterojunctions for piezocatalytic degradation of organic dyes via harvesting ultrasonic vibration energy

BiVO_(4)porous spheres modified by ZnO were designed and synthesized using a facile two-step method.The resulting ZnO/BiVO_(4)composite catalysts have shown remarkable efficiency as piezoelectric catalysts for degrading Rhodamine B(RhB)unde mechanical vibrations,they exhibit superior activity compared to pure ZnO.The 40wt%ZnO/BiVO_(4)heterojunction composite displayed the highest activity,along with good stability and recyclability.The enhanced piezoelectric catalytic activity can be attributed to the form ation of an I-scheme heterojunction structure,which can effectively inhibit the electron-hole recombination.Furthermore,hole(h+)and superoxide radical(·O_(2)^(-))are proved to be the primary active species.Therefore,ZnO/BiVO_(4)stands as an efficient and stable piezoelectric catalyst with broad potential application in the field of environmental water pollution treatment.

Defect Engineering with Rational Dopants Modulation for High‑Temperature Energy Harvesting in Lead‑Free Piezoceramics

High temperature piezoelectric energy harvester(HTPEH)is an important solution to replace chemical battery to achieve independent power supply of HT wireless sensors.However,simultaneously excellent performances,including high figure of merit(FOM),insulation resistivity(ρ)and depolarization temperature(Td)are indispensable but hard to achieve in lead-free piezoceramics,especially operating at 250°C has not been reported before.Herein,well-balanced performances are achieved in BiFeO3–BaTiO3 ceramics via innovative defect engineering with respect to delicate manganese doping.Due to the synergistic effect of enhancing electrostrictive coefficient by polarization configuration optimization,regulating iron ion oxidation state by high valence manganese ion and stabilizing domain orientation by defect dipole,comprehensive excellent electrical performances(Td=340°C,ρ250°C>10^(7)Ωcm and FOM_(250°C)=4905×10^(–15)m^(2)N^(−1))are realized at the solid solubility limit of manganese ions.The HT-PEHs assembled using the rationally designed piezoceramic can allow for fast charging of commercial electrolytic capacitor at 250°C with high energy conversion efficiency(η=11.43%).These characteristics demonstrate that defect engineering tailored BF-BT can satisfy high-end HT-PEHs requirements,paving a new way in developing selfpowered wireless sensors working in HT environments.

Ultra‑High Sensitivity Anisotropic Piezoelectric Sensors for Structural Health Monitoring and Robotic Perception

Monitoring minuscule mechanical signals,both in magnitude and direction,is imperative in many application scenarios,e.g.,structural health monitoring and robotic sensing systems.However,the piezoelectric sensor struggles to satisfy the requirements for directional recognition due to the limited piezoelectric coefficient matrix,and achieving sensitivity for detecting micrometer-scale deformations is also challenging.Herein,we develop a vector sensor composed of lead zirconate titanate-electronic grade glass fiber composite filaments with oriented arrangement,capable of detecting minute anisotropic deformations.The as-prepared vector sensor can identify the deformation directions even when subjected to an unprecedented nominal strain of 0.06%,thereby enabling its utility in accurately discerning the 5μm-height wrinkles in thin films and in monitoring human pulse waves.The ultra-high sensitivity is attributed to the formation of porous ferroelectret and the efficient load transfer efficiency of continuous lead zirconate titanate phase.Additionally,when integrated with machine learning techniques,the sensor’s capability to recognize multi-signals enables it to differentiate between 10 types of fine textures with 100%accuracy.The structural design in piezoelectric devices enables a more comprehensive perception of mechanical stimuli,offering a novel perspective for enhancing recognition accuracy.

Self-Powered Piezo-Supercapacitors Based on ZnO@Mo-Fe-MnO_(2)Nanoarrays

The development of self-charging supercapacitor power cells(SCSPCs)has profound implications for smart electronic devices used in different fields.Here,we epitaxially electrodeposited Mo-and Fe-codoped MnO_(2)films on piezoelectric ZnO nanoarrays(NAs)grown on the flexible carbon cloth(denoted ZnO@Mo-Fe-MnO_(2)NAs).A self-charging supercapacitor power cell device was assembled with the Mo-and Fe-codoped MnO_(2)nanoarray electrode and poly(vinylidenefluoride-co-trifluoroethylene)(PVDF-Trfe)piezoelectric film doped with BaTiO_(3)(BTO)and carbon nanotubes(CNTs)(denoted PVDF-Trfe/CNTs/BTO).The self-charging supercapacitor power cell device exhibited an energy density of 30μWh cm^(-2)with a high power density of 40 mW cm^(-2)and delivered an excellent self-charging performance of 363 mV(10 N)driven by both the piezoelectric ZnO nanoarrays and the poly(vinylidenefluoride-co-trifluoroethylene)piezoelectric film doped with BaTiO_(3)and carbon nanotubes.More intriguingly,the device could also be self-charged by 184 mV due to residual stress alone and showed excellent energy conversion efficiency and low self-discharge rate.This work illustrates for the first time the self-charging mechanism involving electrolyte ion migration driven by both electrodes and films.A comprehensive analysis strongly confirmed the important contribution of the piezoelectric ZnO nanoarrays in the self-charging process of the self-charging supercapacitor power cell device.This work provides novel directions and insights for the development of selfcharging supercapacitor power cells.

Analysis of piezoelectric semiconductor fibers under gradient temperature changes

Piezoelectric semiconductors(PSs)possess both semiconducting properties and piezoelectric coupling effects,making them optimal building blocks for semiconductor devices.PS fiber-like structures have wide applications in multi-functional semiconductor devices.In this paper,a one-dimensional(1D)theoretical model is established to describe the piezotronic responses of a PS fiber under gradient temperature changes.The theoretical model aims to explain the mechanism behind the resistance change caused by such gradient temperature changes.Numerical results demonstrate that a gradient temperature change significantly affects the physical fields within the PS fiber,and can induce changes in its surface resistance.It provides important theoretical guidance on the development of piezotronic devices that are sensitive to temperature effects.

Dynamic and electrical responses of a curved sandwich beam with glass reinforced laminate layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact

The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate(GRL)layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact(LVI)are investigated.The current study aims to carry out a dynamic analysis on the sandwich beam when the impactor hits the top face sheet with an initial velocity.For the layer analysis,the high-order shear deformation theory(HSDT)and Frostig's second model for the displacement fields of the core layer are used.The classical non-adhesive elastic contact theory and Hunter's principle are used to calculate the dynamic responses in terms of time.In order to validate the analytical method,the outcomes of the current investigation are compared with those gained by the experimental tests carried out by other researchers for a rectangular composite plate subject to the LVI.Finite element(FE)simulations are conducted by means of the ABAQUS software.The effects of the parameters such as foam modulus,layer material,fiber angle,impactor mass,and its velocity on the generated voltage are reviewed.

Self-recoverable NIR mechanoluminescence from Cr^(3+) doped perovskite type aluminate

Mechanoluminescent(ML)materials,which have the ability to convert mechanical energy to optical energy,have found huge promising applications such as in stress imaging and anti-counterfeiting.However,the main reported ML phosphors are based on trap-related ones,thus hindering the practical applications due to the requirement of complex light pre-irradiation process.Here,a self-recoverable near infrared(NIR)ML material of Lali-xO:xCr^(3+)(x=0.2%,0.4%,0.6%,0.8%,1.0%,and 1.2%)has been developed.Based on the preheating method and corresponding ML performance analysis,the influences of residual carriers are eliminated and the detailed dynamic luminescence process analysis is realized.Systematic experiments are conducted to reveal the origin of the ML emissions,demonstrating that ML is dictated more by the non-centrosymmetric piezoelectric crystal characteristic.In general,this work has provided significant references for exploring more efficient NIR ML materials,which may provide potential applications in anti-counterfeiting and bio-stress sensing.

Progress in the research on organic piezoelectric catalysts for dye decomposition

Organic contaminants have posed a direct and substantial risk to human wellness and the environment.In recent years,piezo-electric catalysis has evolved as a novel and effective method for decomposing these contaminants.Although piezoelectric materials offer a wide range of options,most related studies thus far have focused on inorganic materials and have paid little attention to organic materi-als.Organic materials have advantages,such as being lightweight,inexpensive,and easy to process,over inorganic materials.Therefore,this paper provides a comprehensive review of the progress made in the research on piezoelectric catalysis using organic materials,high-lighting their catalytic efficiency in addressing various pollutants.In addition,the applications of organic materials in piezoelectric cata-lysis for water decomposition to produce hydrogen,disinfect bacteria,treat tumors,and reduce carbon dioxide are presented.Finally,fu-ture developmental trends regarding the piezoelectric catalytic potential of organic materials are explored.

The marriage of immunomodulatory,angiogenic,and osteogenic capabilities in a piezoelectric hydrogel tissue engineering scafold for military medicine

Background:Most bone-related injuries to grassroots troops are caused by training or accidental injuries.To establish preventive measures to reduce all kinds of trauma and improve the combat effectiveness of grassroots troops,it is imperative to develop new strategies and scafolds to promote bone regeneration.Methods:In this study,a porous piezoelectric hydrogel bone scafold was fabricated by incorporating polydopamine(PDA)-modified ceramic hydroxyapatite(PDA-hydroxyapatite,PHA)and PDA-modified barium titanate(PDABaTiO_(3),PBT)nanoparticles into a chitosan/gelatin(Cs/Gel)matrix.The physical and chemical properties of the Cs/Gel/PHA scafold with 0–10 wt%PBT were analyzed.Cell and animal experiments were performed to characterize the immunomodulatory,angiogenic,and osteogenic capabilities of the piezoelectric hydrogel scafold in vitro and in vivo.Results:The incorporation of BaTiO_(3) into the scafold improved its mechanical properties and increased self-generated electricity.Due to their endogenous piezoelectric stimulation and bioactive constituents,the prepared Cs/Gel/PHA/PBT hydrogels exhibited cytocompatibility as well as immunomodulatory,angiogenic,and osteogenic capabilities;they not only effectively induced macrophage polarization to M2 phenotype but also promoted the migration,tube formation,and angiogenic differentiation of human umbilical vein endothelial cells(HUVECs)and facilitated the migration,osteodifferentiation,and extracellular matrix(ECM)mineralization of MC3T3-E1 cells.The in vivo evaluations showed that these piezoelectric hydrogels with versatile capabilities significantly facilitated new bone formation in a rat large-sized cranial injury model.The underlying molecular mechanism can be partly attributed to the immunomodulation of the Cs/Gel/PHA/PBT hydrogels as shown via transcriptome sequencing analysis,and the PI3K/Akt signaling axis plays an important role in regulating macrophage M2 polarization.Conclusion:The piezoelectric Cs/Gel/PHA/PBT hydrogels developed here with favorable immunomodulation,angiogenesis,and osteogenesis functions may be used as a substitute in periosteum injuries,thereby offering the novel strategy of applying piezoelectric stimulation in bone tissue engineering for the enhancement of combat efectiveness in grassroots troops.

Piezotronic neuromorphic devices:principle,manufacture,and applications

With the arrival of the era of artificial intelligence(AI)and big data,the explosive growth of data has raised higher demands on computer hardware and systems.Neuromorphic techniques inspired by biological nervous systems are expected to be one of the approaches to breaking the von Neumann bottleneck.Piezotronic neuromorphic devices modulate electrical transport characteristics by piezopotential and directly associate external mechanical motion with electrical output signals in an active manner,with the capability to sense/store/process information of external stimuli.In this review,we have presented the piezotronic neuromorphic devices(which are classified into strain-gated piezotronic transistors and piezoelectric nanogenerator-gated field effect transistors based on device structure)and discussed their operating mechanisms and related manufacture techniques.Secondly,we summarized the research progress of piezotronic neuromorphic devices in recent years and provided a detailed discussion on multifunctional applications,including bionic sensing,information storage,logic computing,and electrical/optical artificial synapses.Finally,in the context of future development,challenges,and perspectives,we have discussed how to modulate novel neuromorphic devices with piezotronic effects more effectively.It is believed that the piezotronic neuromorphic devices have great potential for the next generation of interactive sensation/memory/computation to facilitate the development of the Internet of Things,AI,biomedical engineering,etc.

Piezoelectric-enhanced n-TiO_(2)/BaTiO_(3)/p-TiO_(2) heterojunction for highly efficient photoelectrocatalysis

Charge separation is critical for achieving efficient solar-to-hydrogen conversion,whereas piezoelectric-enhanced photoelectrochemical(PEC)systems can effectively modulate band bending and charge migration.Herein,we design an n-TiO_(2)/Ba TiO_(3)/p-TiO_(2)(TBTm)heterojunction in which the piezoelectric Ba TiO_(3) layer is sandwiched between n-TiO_(2)and p-TiO_(2).The built-in electric field of TBTm can provide a strong driving force to accelerate carrier separation and prolong carrier lifetime.Consequently,the TBT3 achieves a prominent photocurrent density,as high as 2.13 m A cm^(-2)at 1.23 V versus reversible hydrogen electrode(RHE),which is 2.4-and 1.5-times higher than TiO_(2) and TiO_(2)–Ba TiO_(3) heterojunction,respectively.Driven by mechanical deformation,the induced dipole polarization can further regulate built-in electric fields,and the piezoelectric photocurrent density of TBT3-800 is 2.84 times higher than TiO_(2) at 1.23 V vs.RHE due to the construction of piezoelectric-heterostructures.This work provides a piezoelectric polarization strategy for modulating the built-in electric field of heterojunction for PEC system.

Synchronization and firing mode transition of two neurons in a bilateral auditory system driven by a high–low frequency signal

The FitzHugh–Nagumo neuron circuit integrates a piezoelectric ceramic to form a piezoelectric sensing neuron,which can capture external sound signals and simulate the auditory neuron system.Two piezoelectric sensing neurons are coupled by a parallel circuit consisting of a Josephson junction and a linear resistor,and a binaural auditory system is established.Considering the non-singleness of external sound sources,the high–low frequency signal is used as the input signal to study the firing mode transition and synchronization of this system.It is found that the angular frequency of the high–low frequency signal is a key factor in determining whether the dynamic behaviors of two coupled neurons are synchronous.When they are in synchronization at a specific angular frequency,the changes in physical parameters of the input signal and the coupling strength between them will not destroy their synchronization.In addition,the firing mode of two coupled auditory neurons in synchronization is affected by the characteristic parameters of the high–low frequency signal rather than the coupling strength.The asynchronous dynamic behavior and variations in firing modes will harm the auditory system.These findings could help determine the causes of hearing loss and devise functional assistive devices for patients.

Piezoelectric fibers based on silk fibroin with excellent output performance

The self-powered tissue engineering scaffold with good biocompatibility is of great significance for stimulating nerve cell growth.In this study,silk fibroin(SF)-based fibers with regulatable structure and piezoelectric performance are fabricated by dry-spinning and post-treatment.The concentration of SF and calcium ion in spinning dope and the post-treatment affect the conformation transition and crystallinity of SF.As a result,the SF fibers exhibit high piezoelectric coefficient d_(33)(3.24 pm/V)and output voltage(~27 V).Furthermore,these piezoelectric fibers promote the growth of PC-12 cells,demonstrating the promising potential for nerve repair and other energy harvester.

Feedback linearization and equivalent-disturbance compensation control strategy for piezoelectric stage

Piezoelectric stages use piezoelectric actuators and flexure hinges as driving and amplifying mechanisms,respectively.These systems have high positioning accuracy and high-frequency responses,and they are widely used in various precision/ultra-precision positioning fields.However,the main challenge with these devices is the inherent hysteresis nonlinearity of piezoelectric actuators,which seriously affects the tracking accuracy of a piezoelectric stage.Inspired by this challenge,in this work,we developed a Hammerstein model to describe the hysteresis nonlinearity of a piezoelectric stage.In particular,in our proposed scheme,a feedback-linearization algorithm is used to eliminate the static hysteresis nonlinearity.In addition,a composite controller based on equivalent-disturbance compensation was designed to counteract model uncertainties and external disturbances.An analysis of the stability of a closed-loop system based on this feedback-linearization algorithm and composite controller was performed,and this was followed by extensive comparative experiments using a piezoelectric stage developed in the laboratory.The experimental results confirmed that the feedback-linearization algorithm and the composite controller offer improved linearization and trajectory-tracking performance.

Fabricating AC/DC nanogenerators based on single ZnO nanowires by using a nanomanipulator in a scanning electron microscope

Single zinc oxide nanowires(ZnO NWs)are promising for nanogenerators because of their excellent semiconducting and piezoelectric properties,but characterizing the latter efficiently is challenging.As reported here,an electrical breakdown strategy was used to construct single ZnO NWs with a specific length.With the high operability of a nanomanipulator in a scanning electron microscope,ZnO-NW-based twoprobe and three-probe structures were constructed for fabricating AC/DC nanogenerators,respectively.For a ZnO NW,an AC output of between−15.31 mV and 5.82 mV was achieved,while for a DC nanogenerator,an output of24.3 mV was realized.Also,the three-probe structure’s output method was changed to verify the distribution of piezoelectric charges when a single ZnO NW is bent by a probe,and DC outputs of different amplitudes were achieved.This study provides a low-cost,highly convenient,and operational method for studying the AC/DC output characteristics of single NWs,which is beneficial for the further development of nanogenerators.

Natural frequency analysis of laminated piezoelectric beams with arbitrary polarization directions

Piezoelectric devices exhibit unique properties that vary with different vibration modes,closely influenced by their polarization direction.This paper presents an analysis on the free vibration of laminated piezoelectric beams with varying polarization directions,using a state-space-based differential quadrature method.First,based on the electro-elasticity theory,the state-space method is extended to anisotropic piezoelectric materials,establishing state-space equations for arbitrary polarized piezoelectric beams.A semi-analytical solution for the natural frequency is then obtained via the differential quadrature method.The study commences by examining the impact of a uniform polarization direction,and then proceeds to analyze six polarization schemes relevant to the current research and applications.Additionally,the effects of geometric dimensions and gradient index on the natural frequencies are explored.The numerical results demonstrate that varying the polarization direction can significantly influence the natural frequencies,offering distinct advantages for piezoelectric elements with different polarizations.This research provides both theoretical insights and numerical methods for the structural design of piezoelectric devices.

A Single-Layer Piezoelectric Composite Separator for Durable Operation of Li Metal Anode at High Rates

Piezoelectric ceramic and polymeric separators have been proposed to effectively regulate Li deposition and suppress dendrite growth,but such separators still fail to satisfactorily support durable operation of lithium metal batteries owing to the fragile ceramic layer or low-piezoelectricity polymer as employed.Herein,by combining PVDF-HFP and ferroelectric BaTiO_(3),we develop a homogeneous,single-layer composite separator with strong piezoelectric effects to inhibit dendrite growth while maintaining high mechanical strength.As squeezed by local protrusion,the polarized PVDF-HFP/BaTiO_(3)composite separator generates a local voltage to suppress the local-intensified electric field and further deconcentrate regional lithium-ion flux to retard lithium deposition on the protrusion,hence enabling a smoother and more compact lithium deposition morphology than the unpoled composite separator and the pure PVDF-HFP separator,especially at high rates.Remarkably,the homogeneous incorporation of BaTiO_(3)highly improves the piezoelectric performances of the separator with residual polarization of 0.086 pC cm^(-2)after polarization treatment,four times that of the pure PVDF-HFP separator,and simultaneously increases the transference number of lithium-ion from 0.45 to 0.57.Beneficial from the prominent piezoelectric mechanism,the polarized PVDF-HFP/BaTiO_(3)composite separator enables stable cyclic performances of Li||LiFePO_(4)cells for 400 cycles at 2 C(1 C=170 mA g^(-1))with a capacity retention above 99%,and for 600 cycles at 5 C with a capacity retention over 85%.

Analytical modeling of piezoelectric meta-beams with unidirectional circuit for broadband vibration attenuation

Broadband vibration attenuation is a challenging task in engineering since it is difficult to achieve low-frequency and broadband vibration control simultaneously.To solve this problem,this paper designs a piezoelectric meta-beam with unidirectional electric circuits,exhibiting promising broadband attenuation capabilities.An analytical model in a closed form for achieving the solution of unidirectional vibration transmission of the designed meta-beam is developed based on the state-space transfer function method.The method can analyze the forward and backward vibration transmission of the piezoelectric meta-beam in a unified manner,providing reliable dynamics solutions of the beam.The analytical results indicate that the meta-beam effectively reduces the unidirectional vibration across a broad low-frequency range,which is also verified by the solutions obtained from finite element analyses.The designed meta-beam and the proposed analytical method facilitate a comprehensive investigation into the distinctive unidirectional transmission behavior and superb broadband vibration attenuation performance.

Indentation behavior of a semi-infinite piezoelectric semiconductor under a rigid flat-ended cylindrical indenter

This paper theoretically studies the axisymmetric frictionless indentation of a transversely isotropic piezoelectric semiconductor(PSC)half-space subject to a rigid flatended cylindrical indenter.The contact area and other surface of the PSC half-space are assumed to be electrically insulating.By the Hankel integral transformation,the problem is reduced to the Fredholm integral equation of the second kind.This equation is solved numerically to obtain the indentation behaviors of the PSC half-space,mainly including the indentation force-depth relation and the electric potential-depth relation.The results show that the effect of the semiconductor property on the indentation responses is limited within a certain range of variation of the steady carrier concentration.The dependence of indentation behavior on material properties is also analyzed by two different kinds of PSCs.Finite element simulations are conducted to verify the results calculated by the integral equation technique,and good agreement is demonstrated.

Existence and numerical approximation of a solution to frictional contact problem for electro-elastic materials

In this paper,a frictional contact problem between an electro-elastic body and an electrically conductive foundation is studied.The contact is modeled by normal compliance with finite penetration and a version of Coulomb’s law of dry friction in which the coefficient of friction depends on the slip.In addition,the effects of the electrical conductivity of the foundation are taken into account.This model leads to a coupled system of the quasi-variational inequality of the elliptic type for the displacement and the nonlinear variational equation for the electric potential.The existence of a weak solution is proved by using an abstract result for elliptic variational inequalities and a fixed point argument.Then,a finite element approximation of the problem is presented.Under some regularity conditions,an optimal order error estimate of the approximate solution is derived.Finally,a successive iteration technique is used to solve the problem numerically and a convergence result is established.