CONSPECTUS:Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)is a derivative of polythiophene and an intrinsically conductive polymer(CP).Due to its excellent conductivity,processability,and biocompati...CONSPECTUS:Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)is a derivative of polythiophene and an intrinsically conductive polymer(CP).Due to its excellent conductivity,processability,and biocompatibility,it has received widespread attention in the past decade and has become a popular material for wearable electronic devices.Thin films and fibers are the two primary dimensions that PEDOT:PSS has been made into.Compared with two-dimensional(2D)thin films,1D fibers have natural advantages in integration and structural design,remarkably accelerating practical applications.Wet spinning has been considered the primary method to fabricate 1D PEDOT:PSS fibers,which can continuously produce fibers on a large scale with the outstanding capability of fine-tuning the compositions and morphologies to achieve the desired properties.For example,untreated wet-spun PEDOT:PSS fibers generally have relatively lower conductivity(0.1 S·cm−1),while the coagulation bath obtained by mixing acetone and isopropanol significantly increases the conductivity(310 S·cm−1),which has become a classic combination.Nevertheless,the extensive use of such solvents does not meet the requirements of environmental friendliness,and researchers have been searching for suitable alternatives.Even though the coagulation bath composed of ethanol,water,and metal salts compensates for improving that,the performance needs further enhancement,including conductivity,elongation at break,and capacitance.Thus,intensive efforts have been taken to boost the performance of PEDOT:PSS by changing the formula of the coagulation bath,blending other additives with the starting materials,and secondary treatment for the obtained fibers.In addition to ethanol and water,other coagulation baths are also being developed,such as sulfuric acid,N,N-dimethylacetamide,etc.,which play a critical role in the above solutions due to the excellent performance of the resultant fibers.In this Account,the efforts are mainly concentrated on the advancements and progress in achieving high-performance wet-spun PEDOT:PSS fibers,from coagulation bath regulation to secondary treatment of spinning solution blending.The fundamental electrochemistry and challenges of PEDOT:PSS fibers will also be discussed.It will then focus on the advantages and control mechanisms of preparing PEDOT:PSS fibers through wet spinning from three perspectives:(i)coagulation bath control;(ii)polymer blending;and(iii)post-treatment.For example,we will discuss:1)how different additives in the coagulation bath regulate the structure and properties of PEDOT:PSS fibers;2)how polymer blending can improve the stability and durability of PEDOT:PSS fibers;and 3)how post-treatment can endow PEDOT:PSS fibers with unique structures,enhancing their strength and conductivity.Finally,the key research directions required in this field and the remaining challenges to be addressed will be summarized and proposed.展开更多
Zinc oxide(ZnO),as a broadband gap semiconductor material,exhibits unique physical and chemical properties that make it highly suitable for optoelectronics,piezoelectric devices,and gas-sensitive sensors,showing signi...Zinc oxide(ZnO),as a broadband gap semiconductor material,exhibits unique physical and chemical properties that make it highly suitable for optoelectronics,piezoelectric devices,and gas-sensitive sensors,showing significant potential for various applications.This paper focuses on the regulation and application of ZnO-based p-n junctions and piezoelectric devices.It discusses in detail the preparation of ZnO materials,the construction of p-n junctions,the optimization of piezoelectric device performance,and its application in various fields.By employing different preparation methods and strategies,high-quality ZnO thin films can be grown,and effective control of p-type conductivity achieved.This study provides both a theoretical foundation and technical support for controlling the performance of ZnO-based piezoelectric devices,as well as paving new pathways for the broader application of ZnO materials.展开更多
Flexible piezoelectric energy harvesters(PEHs)have gained lots of attention in recent years,because of their potential biomechanical applications,such as powering implantable devices.Several in vivo animal experiments...Flexible piezoelectric energy harvesters(PEHs)have gained lots of attention in recent years,because of their potential biomechanical applications,such as powering implantable devices.Several in vivo animal experiments have demonstrated that the output power of a flexible PEH varies remarkably with patching orientations and locations,but the underlying mechanism remains unclear yet.Herein,an electromechanical model for a flexible PEH installed on a beating heart is proposed,and a concise relationship between the output power of the device and myocardium strain is established.The results demonstrate that the patching orientations have a significant impact on the output power of the PEH,and the optimal patching orientations for all patching locations are approximately 15–20 degree for PEHs mounted on the left ventricle.The simple theoretical method provided here would be universally effective for choosing the optimal patching locations and orientations of flexible PEHs installed on a nonhomogeneous deformed surface.展开更多
The diffusion and dynamic behaviors of liquid metal droplet during impact significantly affect its application in 3D printing and painting processes.To obtain a better understanding of the impact process of liquid met...The diffusion and dynamic behaviors of liquid metal droplet during impact significantly affect its application in 3D printing and painting processes.To obtain a better understanding of the impact process of liquid metal droplets,we analyze the influence of different initial conditions and substrate materials on droplet spreading,impact force,and elastic wave propagation on the substrate.It is found that an agglomeration phenomenon can be observed when the liquid metal droplets impact onto a soft elastomer substrate,which is not observed as a metal substrate is employed.Regardless of the substrate material,when surface tension dominates the diffusion,the diffusion factor of droplets is proportional to We(Weber number).It is also observed that the self-similarity of liquid metal droplet impact force on copper substrates,which is not the case for soft elastomer substrates.Using smoothed particle hydrodynamics(SPH)simulations,the time-domain curve and peak point of the droplet can be well predicted for a metal substrate.Furthermore,by recording the acceleration signal on the substrates,we further obtain the energy radiated by elastic waves,providing an explanation for energy conversion during the impact process with varying parameters.The results provide an additional understanding on the complex impact behaviors of liquid metal droplets.展开更多
Due to scale effects,micromechanical resonators offer an excellent platform for investigating the intrinsic mechanisms of nonlinear dynamical phenomena and their potential applications.This review focuses on mode-coup...Due to scale effects,micromechanical resonators offer an excellent platform for investigating the intrinsic mechanisms of nonlinear dynamical phenomena and their potential applications.This review focuses on mode-coupled micromechanical resonators,highlighting the latest advancements in four key areas:internal resonance,synchronization,frequency combs,and mode localization.The origin,development,and potential applications of each of these dynamic phenomena within mode-coupled micromechanical systems are investigated,with the goal of inspiring new ideas and directions for researchers in this field.展开更多
Mechanical metamaterials are artificial materials that control their macroscopic properties using repetitive units rather than chemical constituents.Through rational design and spatial arrangement of the unit cells,me...Mechanical metamaterials are artificial materials that control their macroscopic properties using repetitive units rather than chemical constituents.Through rational design and spatial arrangement of the unit cells,mechanical metamaterials can realize a range of counterintuitive properties on a larger scale.In this work,a type of mechanical metamaterial unit cell is proposed,exhibiting both compression-twist coupling behavior and bistability that can be programmed.The design involves linking two cylindrical frames with topology-designed inclined beams.Under uniaxial loading,the structure undergoes a compression-twist deformation,along with buckling at two joints of the inclined beams.Through a rational design of the unit's geometric parameters,the structure can retain its deformed state once the applied displacement surpasses a specified threshold,showing a programmed bistable characteristic.We investigated the influence of the involved parameters on the mechanical response of the unit cells numerically,which agrees well with our experimental results.Since the inclined beams dominate the elastic deformation of unit cells,the two cylindrical frames are almost independent of the bistable response and can therefore be designed in any shape for various arrangements of unit cells in multi-dimensional space.展开更多
The inflation tests of rubbery membranes have been widely employed as an efficient method to characterize the stress response as biaxial loading states.However,most of the previous theoretical works have employed clas...The inflation tests of rubbery membranes have been widely employed as an efficient method to characterize the stress response as biaxial loading states.However,most of the previous theoretical works have employed classic hyperelastic models to analyze the deformation behaviors of inflated membranes.The classic models have been demonstrated to lack the ability to capturing the biaxial deformation of rubbers.To address this issue,we have combined the analytical method and the finite element simulation to investigate the deformation response of soft membranes with different constitutive relationships.For the analytical method,the governing ordinary differential equations have been set up for the boundary value problem of inflation tests and further solved using the shooting method.The analytical results are consistent with those obtained from finite element simulation.The results show that the deformation belongs to the unequal biaxial condition rather than the equi-biaxial state unless a neo-Hookean model is adopted.We also perform a parameter study using the extended eight-chain model,which shows that a change in different parameters affects the mechanical response of inflation tests variously.This work may shed light on the future experimental characterization of soft materials using inflation experiments.展开更多
Kirigami,through introducing cuts into a thin sheet,can greatly improve the stretchability of structures and also generate complex patterns,showing potentials in various applications.Interestingly,even with the same c...Kirigami,through introducing cuts into a thin sheet,can greatly improve the stretchability of structures and also generate complex patterns,showing potentials in various applications.Interestingly,even with the same cutting pattern,the mechanical response of kirigami metamaterials can exhibit significant differences depending on the cutting angles in respect to the loading direction.In this work,we investigate the structural deformation of kirigami metamaterials with square domains and varied cutting angles of 0°and 45°.We further introduce a second level of cutting on the basis of the first cutting pattern.By combining experiments and finite element simulations,it is found that,compared to the commonly used 0°cuts,the two-level kirigami metamaterials with 45°cuts exhibit a unique alternating arrangement phenomenon of expanded/unexpanded states in the loading process,which also results in distinct stress–strain response.Through tuning the cutting patterns of metamaterials with 45°cuts,precise control of the rotation of the kirigami unit is realized,leading to kirigami metamaterials with encryption properties.The current work demonstrates the programmability of structural deformation in hierarchical kirigami metamaterials through controlling the local cutting modes.展开更多
This article investigates the second overtone thickness-extensional(TE2)vibrations and associated mode-coupling behaviors in ZnO piezoelectric film bulk acoustic resonator(FBAR),utilizing its wave dispersion relation ...This article investigates the second overtone thickness-extensional(TE2)vibrations and associated mode-coupling behaviors in ZnO piezoelectric film bulk acoustic resonator(FBAR),utilizing its wave dispersion relation and the higher-order stress balance principle.By superimposing the general wave solutions of multiple eigenmodes within the frequency range of the TE2 mode,mode-coupling solutions for ZnO FBAR are constructed.The substitution of these mode-coupling solutions into the higher-order stress balance principle,as laterally weak boundary conditions,leads to the frequency spectrogram equation,determining the relationship between resonance frequency and plate length-to-thickness ratio.A modified algorithm that combines the bisection method and the complex modulus ratio method is developed to solve the dispersion equation and frequency spectrogram equation(namely a kind of 2D complex transcendental equations)accurately and efficiently.The obtained results indicate that the operational TE2 mode may couple to unwanted 3^(rd)thickness-shear,fundamental thickness-shear,and flexural modes.Moreover,the mode-coupling behaviors depend strongly on resonance frequencies and plate length-to-thickness ratio.The displacement distributions of total displacement components,alongside the main displacement com-ponents of all considered eigenmodes,clearly demonstrate the variety of coupling behaviors.According to the obtained frequency spectrograms,the desirable values of plate length-to-thickness ratio for a clean operating mode with very weak coupling intensity are determined.These findings are of vital importance for the understanding of the mode-coupling me-chanism in overtone thickness-extensional FBARs,which will facilitate the structural design and optimization of FBAR devices.展开更多
We study the axisymmetric frictionless indentation problem of a piezoelectric semiconductor(PSC)thin film perfectly bonded to a semi-infinite isotropic elastic substrate by a rigid and insulating spherical indenter.Th...We study the axisymmetric frictionless indentation problem of a piezoelectric semiconductor(PSC)thin film perfectly bonded to a semi-infinite isotropic elastic substrate by a rigid and insulating spherical indenter.The Hankel integral transformation is first employed to derive the general solutions for the governing differential equations of the PSC film and elastic substrate.Then,using the boundary and interface conditions,the complicated indentation problem is reduced to numerically solve a Fredholm integral equation of the second kind.Numerical results are given to demonstrate the effects of semiconducting property,film thickness as well as Young’s modulus and Poisson’s ratio of the substrate on the indentation responses.The obtained findings will contribute to the establishment of indentation experiments for PSC film/substrate systems.展开更多
Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have...Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have developed a modeling framework to simulate the stochastic and cooperative behaviors of growing actin networks in propelling obstacles, with an emphasis on the size and shape effects on work capacity and filament orientation in the growing process. Our results show that the characteristic size of obstacles changes the protrusion power per unit length, without influencing the orientation distribution of actin filaments in growing networks. In contrast, the geometry of obstacles has a profound effect on filament patterning, which influences the orientation of filaments differently when the drag coefficient of environment is small, intermediate, or large. We also discuss the role of various parameters, such as the aspect ratio of obstacles, branching rate, and capping rate, in affecting the protrusion power of network growth.展开更多
The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexago...The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexagonally packed and interconnected via cross-linking proteins including α-actinin, filamin, and fascin. As pushing against the plasma membrane and/or external barriers, the actin bundles in filopodial protrusion inevitably encounter a compressive load. The bending stiffness and buckling stability of actin bundles are therefore important in determining the filopodia architecture and subsequent cell morphology. In this work, we employ a coarse-grained molecular dynamics model to investigate the buckling behaviors of cross-linked actin bundles under compression, which explicitly accounts for the properties of constituent filaments and the mechanical descriptions of cross-linkers. The bending stiffness of actin bundles exhibits a generic size effect depending on the number of filaments in the bundles, explicitly depending on the degree of inter-filament coupling. The distinct buckling modes are analyzed for bundles with different coupling states and strengths of cross-linkers. This study could clarify the stability and buckling mechanisms of parallelly packed actin bundles and the structure-function relations of mechanical components in filopodial protrusion.展开更多
An actual ecological predator-prey system often undergoes random environmental mutations owing to the impact of natural disasters and man-made destruction, which may destroy the balance between the species. In this pa...An actual ecological predator-prey system often undergoes random environmental mutations owing to the impact of natural disasters and man-made destruction, which may destroy the balance between the species. In this paper,the stochastic dynamics of the nonlinear predator-prey system considering random environmental mutations is investigated, and a feedback control strategy is proposed to reshape the response of the predator-prey system against random abrupt environmental mutations. A delayed Markov jump system(MJS) is established to model such a predator-prey system. A novel first integral is constructed which leads to better approximation solutions of the ecosystem. Then, by applying the stochastic averaging method based on this novel first integral, the stochastic response of the predator-prey system is investigated, and an analytical feedback control is designed to reshape the response of the ecosystem from the disturbed state back to the undisturbed one.Numerical simulations finally illustrate the accuracy and effectiveness of the proposed procedure.展开更多
Developing robotic manipulators capable of performing effective physical interac- tion tasks is a challenging topic. In this study, we design a soft robotic arm （SRA） with multiple degrees of freedom inspired by the...Developing robotic manipulators capable of performing effective physical interac- tion tasks is a challenging topic. In this study, we design a soft robotic arm （SRA） with multiple degrees of freedom inspired by the flexible structures and the unique motion mechanism of the octopus arm. The SRA is fabricated with elastomeric materials, which consists of four series of integrated pneumatic chambers that play similar roles as the muscles in the octopus arm can achieve large bending in various directions with variable stiffness. This SRA displays specified movements via controlling pressure and selecting channels. Moreover, utilizing parallel control, the SRA demonstrates complicated three-dimensional motions. The force response and motion of the SRA are determined both experimentally and computationally. The applications of the present SRA include tightly coiling around the objects because of its large bending deformation （nearly 360°）, grasping multiple objects, and adjusting the grabbing mode in accordance with the shape of objects.展开更多
Natural muscle provides excellent motilities for animals.As the basic unit of the muscle system,the skeletal muscle fibers function as a soft linear actuator.Inspired by the muscle fibers,researchers have developed va...Natural muscle provides excellent motilities for animals.As the basic unit of the muscle system,the skeletal muscle fibers function as a soft linear actuator.Inspired by the muscle fibers,researchers have developed various soft active devices with linear actuation.This paper reviews several soft linear actu ators,such as the dielec trie elastomer,t hermal responsive hydrogels,pneumatic artificial muscle,and conducting polymers.The actuation mechanisms and performances of these soft linear actuators are summarized.Based on the dielectric elastomer,we propose a design of a hybrid system with linear actuation,driven by both the electric motor and dielectric elasto mer cone.The elec tromechanical behaviors of the dielec trie elastomer cone have been investigated in both experiment and finite element analysis.This work may guide the further design of soft actuators and robots.展开更多
We study electromechanical fields near the interface between a circular piezoelectric semiconductor cylinder and another piezoelectric semiconductor in which it is embedded. The cylinder is p-doped. The surrounding ma...We study electromechanical fields near the interface between a circular piezoelectric semiconductor cylinder and another piezoelectric semiconductor in which it is embedded. The cylinder is p-doped. The surrounding material is n-doped. The phenomenological theory of piezoelectric semiconductors consisting of the equations of piezoelectricity and the conservation of charge for holes and electrons is used. The theory is linearized for small carrier concentration perturbations. An analytical solution is obtained, showing the formation of a PN junction near the interface. Various electromechanical fields associated with the junction are calculated. The effects of a few physical parameters are examined.展开更多
The effect of piezoelectricity on phonon properties and thermal conductivity of gallium nitride （GaN） nanofilms is theoretically investigated. The elasticity model is utilized to derive the phonon properties in spat...The effect of piezoelectricity on phonon properties and thermal conductivity of gallium nitride （GaN） nanofilms is theoretically investigated. The elasticity model is utilized to derive the phonon properties in spatially confined GaN nanofilms. The piezoelectric constitutive relation in GaN nanofilms is taken into account in calculating the phonon dispersion relation. The modified phonon group velocity and phonon density of state as well as the phonon thermal conductivity are also obtained due to the contribution of piezoelectricity. Theoretical results show that the piezoelectricity in GaN nanofilms can change significantly the phonon properties such as the phonon group velocity and density of states, resulting in the variation of the phonon thermal conductivity of GaN nanofilms remarkably. Moreover, the piezoelectricity of GaN can modify the dependence of thermal conductivity on the geometrical size and temperature. These results can be useful in modeling the thermal performance in the active region of GaN-based electronic devices.展开更多
A plastic may degrade in response to a trigger.The kinetics of degradation have long been characterized by the loss of weight and strength over time.These methods of gross characterization,however,are misleading when ...A plastic may degrade in response to a trigger.The kinetics of degradation have long been characterized by the loss of weight and strength over time.These methods of gross characterization,however,are misleading when plastic degrades heterogeneously.Here,we study heterogeneous degradation in an extreme form:the growth of a crack under the combined action of chemistry and mechanics.An applied load opens the crack,exposes the crack front to chemical attack,and causes the crack to outrun gross degradation.We studied the crack growth in polylactic acid(PLA),a polyester in which ester bonds break by hydrolysis.We cut a crack in a PLA film using scissors,tore it using an apparatus,and recorded the crack growth using a camera through a microscope.In our testing range,the crack velocity was insensitive to load but was sensitive to humidity and pH.These findings will aid the development of degradable plastics for healthcare and sustainability.展开更多
Parkinson’s disease(PD)is the second most common and fastest-growing neurodegenerative disorder.In recent years,it has been recognized that neurotransmitters other than dopamine and neuronal systems outside the basal...Parkinson’s disease(PD)is the second most common and fastest-growing neurodegenerative disorder.In recent years,it has been recognized that neurotransmitters other than dopamine and neuronal systems outside the basal ganglia are also related to PD pathogenesis.However,little is known about whether and how the caudal zona incerta(ZIc)regulates parkinsonian motor symptoms.Here,we showed that specific glutamatergic but not GABAergic ZIc^(VgluT2) neurons regulated these symptoms.ZIc^(VgluT2) neuronal activation induced time-locked parkinsonian motor symptoms.In mouse models of PD,the ZIc^(VgluT2) neurons were hyperactive and inhibition of their activity ameliorated the motor deficits.ZIc^(VgluT2) neurons monosynaptically projected to the substantia nigra pars reticulata.Incerta-nigral circuit activation induced parkinsonian motor symptoms.Together,our findings provide a direct link between the ZIc,its glutamatergic neurons,and parkinsonian motor symptoms for the first time,help to better understand the mechanisms of PD,and supply a new important potential therapeutic target for PD.展开更多
The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is der...The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is derived with the consideration of both the nonlocal and the active control effects. The numerical results show that the nonlocal effect can effectively enhance the frequency in the middle part of the dispersion curve.When the nonlocal effect is strong enough, zero and negative group velocities will be evoked at different points along the dispersion curve, which will provide different ways of transporting energy including the forward-propagation, localization, and backwardpropagation of wavepackets related to the phase velocity. Both the nonlinear effect and the active control can enhance the frequency, but neither of them is able to produce zero or negative group velocities. Specifically, the active control enhances the frequency of the dispersion curve including the point at which the reduced wave number equals zero, and therefore gives birth to a nonzero cutoff frequency and a band gap in the low frequency range. With a combinational adjustment of all these effects, the wave propagation behaviors can be comprehensively controlled, and energy transferring can be readily manipulated in various ways.展开更多
基金support from the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Yangzhou University)(SJCX23_1909).
文摘CONSPECTUS:Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)is a derivative of polythiophene and an intrinsically conductive polymer(CP).Due to its excellent conductivity,processability,and biocompatibility,it has received widespread attention in the past decade and has become a popular material for wearable electronic devices.Thin films and fibers are the two primary dimensions that PEDOT:PSS has been made into.Compared with two-dimensional(2D)thin films,1D fibers have natural advantages in integration and structural design,remarkably accelerating practical applications.Wet spinning has been considered the primary method to fabricate 1D PEDOT:PSS fibers,which can continuously produce fibers on a large scale with the outstanding capability of fine-tuning the compositions and morphologies to achieve the desired properties.For example,untreated wet-spun PEDOT:PSS fibers generally have relatively lower conductivity(0.1 S·cm−1),while the coagulation bath obtained by mixing acetone and isopropanol significantly increases the conductivity(310 S·cm−1),which has become a classic combination.Nevertheless,the extensive use of such solvents does not meet the requirements of environmental friendliness,and researchers have been searching for suitable alternatives.Even though the coagulation bath composed of ethanol,water,and metal salts compensates for improving that,the performance needs further enhancement,including conductivity,elongation at break,and capacitance.Thus,intensive efforts have been taken to boost the performance of PEDOT:PSS by changing the formula of the coagulation bath,blending other additives with the starting materials,and secondary treatment for the obtained fibers.In addition to ethanol and water,other coagulation baths are also being developed,such as sulfuric acid,N,N-dimethylacetamide,etc.,which play a critical role in the above solutions due to the excellent performance of the resultant fibers.In this Account,the efforts are mainly concentrated on the advancements and progress in achieving high-performance wet-spun PEDOT:PSS fibers,from coagulation bath regulation to secondary treatment of spinning solution blending.The fundamental electrochemistry and challenges of PEDOT:PSS fibers will also be discussed.It will then focus on the advantages and control mechanisms of preparing PEDOT:PSS fibers through wet spinning from three perspectives:(i)coagulation bath control;(ii)polymer blending;and(iii)post-treatment.For example,we will discuss:1)how different additives in the coagulation bath regulate the structure and properties of PEDOT:PSS fibers;2)how polymer blending can improve the stability and durability of PEDOT:PSS fibers;and 3)how post-treatment can endow PEDOT:PSS fibers with unique structures,enhancing their strength and conductivity.Finally,the key research directions required in this field and the remaining challenges to be addressed will be summarized and proposed.
基金The Natural Science Foundation of Guangdong Province(Project No.2023A1515012352)。
文摘Zinc oxide(ZnO),as a broadband gap semiconductor material,exhibits unique physical and chemical properties that make it highly suitable for optoelectronics,piezoelectric devices,and gas-sensitive sensors,showing significant potential for various applications.This paper focuses on the regulation and application of ZnO-based p-n junctions and piezoelectric devices.It discusses in detail the preparation of ZnO materials,the construction of p-n junctions,the optimization of piezoelectric device performance,and its application in various fields.By employing different preparation methods and strategies,high-quality ZnO thin films can be grown,and effective control of p-type conductivity achieved.This study provides both a theoretical foundation and technical support for controlling the performance of ZnO-based piezoelectric devices,as well as paving new pathways for the broader application of ZnO materials.
基金the National Natural Science Foundation of China(Grant No.11902168)the Technology Innovation 2025 Program of Municipality of Ningbo(Grant No.2019B10222)the National Natural Science Foundation of China(Grant No.11925206).
文摘Flexible piezoelectric energy harvesters(PEHs)have gained lots of attention in recent years,because of their potential biomechanical applications,such as powering implantable devices.Several in vivo animal experiments have demonstrated that the output power of a flexible PEH varies remarkably with patching orientations and locations,but the underlying mechanism remains unclear yet.Herein,an electromechanical model for a flexible PEH installed on a beating heart is proposed,and a concise relationship between the output power of the device and myocardium strain is established.The results demonstrate that the patching orientations have a significant impact on the output power of the PEH,and the optimal patching orientations for all patching locations are approximately 15–20 degree for PEHs mounted on the left ventricle.The simple theoretical method provided here would be universally effective for choosing the optimal patching locations and orientations of flexible PEHs installed on a nonhomogeneous deformed surface.
基金supported by the National Natural Science Foundation of China(Grant No.12211530061)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LD22A020001)。
文摘The diffusion and dynamic behaviors of liquid metal droplet during impact significantly affect its application in 3D printing and painting processes.To obtain a better understanding of the impact process of liquid metal droplets,we analyze the influence of different initial conditions and substrate materials on droplet spreading,impact force,and elastic wave propagation on the substrate.It is found that an agglomeration phenomenon can be observed when the liquid metal droplets impact onto a soft elastomer substrate,which is not observed as a metal substrate is employed.Regardless of the substrate material,when surface tension dominates the diffusion,the diffusion factor of droplets is proportional to We(Weber number).It is also observed that the self-similarity of liquid metal droplet impact force on copper substrates,which is not the case for soft elastomer substrates.Using smoothed particle hydrodynamics(SPH)simulations,the time-domain curve and peak point of the droplet can be well predicted for a metal substrate.Furthermore,by recording the acceleration signal on the substrates,we further obtain the energy radiated by elastic waves,providing an explanation for energy conversion during the impact process with varying parameters.The results provide an additional understanding on the complex impact behaviors of liquid metal droplets.
基金supported by the National Key Research and Development Program of China(No.2022YFB3203600)the National Natural Science Foundation of China(Nos.12202355,12132013,and 12172323)the Zhejiang Provincial Natural Science Foundation of China(No.LZ22A020003)。
文摘Due to scale effects,micromechanical resonators offer an excellent platform for investigating the intrinsic mechanisms of nonlinear dynamical phenomena and their potential applications.This review focuses on mode-coupled micromechanical resonators,highlighting the latest advancements in four key areas:internal resonance,synchronization,frequency combs,and mode localization.The origin,development,and potential applications of each of these dynamic phenomena within mode-coupled micromechanical systems are investigated,with the goal of inspiring new ideas and directions for researchers in this field.
基金supported by the National Natural Science Foundation of China(Grant Numbers:12125205,12321002,12072316,12132014)the Zhejiang Provincial Natural Science Foundation of China(LD22A020001).
文摘Mechanical metamaterials are artificial materials that control their macroscopic properties using repetitive units rather than chemical constituents.Through rational design and spatial arrangement of the unit cells,mechanical metamaterials can realize a range of counterintuitive properties on a larger scale.In this work,a type of mechanical metamaterial unit cell is proposed,exhibiting both compression-twist coupling behavior and bistability that can be programmed.The design involves linking two cylindrical frames with topology-designed inclined beams.Under uniaxial loading,the structure undergoes a compression-twist deformation,along with buckling at two joints of the inclined beams.Through a rational design of the unit's geometric parameters,the structure can retain its deformed state once the applied displacement surpasses a specified threshold,showing a programmed bistable characteristic.We investigated the influence of the involved parameters on the mechanical response of the unit cells numerically,which agrees well with our experimental results.Since the inclined beams dominate the elastic deformation of unit cells,the two cylindrical frames are almost independent of the bistable response and can therefore be designed in any shape for various arrangements of unit cells in multi-dimensional space.
基金supported by the National Natural Science Foundation of China(Grant Nos.12211530061 and 12321002)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LD22A020001)the 111 Project(Grant No.B21034).
文摘The inflation tests of rubbery membranes have been widely employed as an efficient method to characterize the stress response as biaxial loading states.However,most of the previous theoretical works have employed classic hyperelastic models to analyze the deformation behaviors of inflated membranes.The classic models have been demonstrated to lack the ability to capturing the biaxial deformation of rubbers.To address this issue,we have combined the analytical method and the finite element simulation to investigate the deformation response of soft membranes with different constitutive relationships.For the analytical method,the governing ordinary differential equations have been set up for the boundary value problem of inflation tests and further solved using the shooting method.The analytical results are consistent with those obtained from finite element simulation.The results show that the deformation belongs to the unequal biaxial condition rather than the equi-biaxial state unless a neo-Hookean model is adopted.We also perform a parameter study using the extended eight-chain model,which shows that a change in different parameters affects the mechanical response of inflation tests variously.This work may shed light on the future experimental characterization of soft materials using inflation experiments.
基金supported by the National Natural Science Foundation of China(Grant Nos.12102392 and 12272341)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ21A020008).
文摘Kirigami,through introducing cuts into a thin sheet,can greatly improve the stretchability of structures and also generate complex patterns,showing potentials in various applications.Interestingly,even with the same cutting pattern,the mechanical response of kirigami metamaterials can exhibit significant differences depending on the cutting angles in respect to the loading direction.In this work,we investigate the structural deformation of kirigami metamaterials with square domains and varied cutting angles of 0°and 45°.We further introduce a second level of cutting on the basis of the first cutting pattern.By combining experiments and finite element simulations,it is found that,compared to the commonly used 0°cuts,the two-level kirigami metamaterials with 45°cuts exhibit a unique alternating arrangement phenomenon of expanded/unexpanded states in the loading process,which also results in distinct stress–strain response.Through tuning the cutting patterns of metamaterials with 45°cuts,precise control of the rotation of the kirigami unit is realized,leading to kirigami metamaterials with encryption properties.The current work demonstrates the programmability of structural deformation in hierarchical kirigami metamaterials through controlling the local cutting modes.
基金supported by the National Natural Science Foundation of China(Grant Nos.12192210,12192211,12102183,12302200,and 12402192)the Natural Science Foundation of Zhejiang Province(Grant No.LD21A020001)+2 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20230873)the National Postdoctoral Program for Innovation Talents(Grant No.BX2021261)supported by the specialized research projects of Huanjiang Laboratory,Zhuji,Zhejiang Province.
文摘This article investigates the second overtone thickness-extensional(TE2)vibrations and associated mode-coupling behaviors in ZnO piezoelectric film bulk acoustic resonator(FBAR),utilizing its wave dispersion relation and the higher-order stress balance principle.By superimposing the general wave solutions of multiple eigenmodes within the frequency range of the TE2 mode,mode-coupling solutions for ZnO FBAR are constructed.The substitution of these mode-coupling solutions into the higher-order stress balance principle,as laterally weak boundary conditions,leads to the frequency spectrogram equation,determining the relationship between resonance frequency and plate length-to-thickness ratio.A modified algorithm that combines the bisection method and the complex modulus ratio method is developed to solve the dispersion equation and frequency spectrogram equation(namely a kind of 2D complex transcendental equations)accurately and efficiently.The obtained results indicate that the operational TE2 mode may couple to unwanted 3^(rd)thickness-shear,fundamental thickness-shear,and flexural modes.Moreover,the mode-coupling behaviors depend strongly on resonance frequencies and plate length-to-thickness ratio.The displacement distributions of total displacement components,alongside the main displacement com-ponents of all considered eigenmodes,clearly demonstrate the variety of coupling behaviors.According to the obtained frequency spectrograms,the desirable values of plate length-to-thickness ratio for a clean operating mode with very weak coupling intensity are determined.These findings are of vital importance for the understanding of the mode-coupling me-chanism in overtone thickness-extensional FBARs,which will facilitate the structural design and optimization of FBAR devices.
基金supported by the National Natural Science Foundation of China(Nos.12072209,U21A20430,12192211,12472155)the S&T Program of Hebei(225676162GH).
文摘We study the axisymmetric frictionless indentation problem of a piezoelectric semiconductor(PSC)thin film perfectly bonded to a semi-infinite isotropic elastic substrate by a rigid and insulating spherical indenter.The Hankel integral transformation is first employed to derive the general solutions for the governing differential equations of the PSC film and elastic substrate.Then,using the boundary and interface conditions,the complicated indentation problem is reduced to numerically solve a Fredholm integral equation of the second kind.Numerical results are given to demonstrate the effects of semiconducting property,film thickness as well as Young’s modulus and Poisson’s ratio of the substrate on the indentation responses.The obtained findings will contribute to the establishment of indentation experiments for PSC film/substrate systems.
基金supported by the National Natural Science Foundation of China (Grants 11321202, 11672268)the Zhejiang Provincial Natural Science Foundation of China (Grant LR16A020001)
文摘Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have developed a modeling framework to simulate the stochastic and cooperative behaviors of growing actin networks in propelling obstacles, with an emphasis on the size and shape effects on work capacity and filament orientation in the growing process. Our results show that the characteristic size of obstacles changes the protrusion power per unit length, without influencing the orientation distribution of actin filaments in growing networks. In contrast, the geometry of obstacles has a profound effect on filament patterning, which influences the orientation of filaments differently when the drag coefficient of environment is small, intermediate, or large. We also discuss the role of various parameters, such as the aspect ratio of obstacles, branching rate, and capping rate, in affecting the protrusion power of network growth.
基金the National Natural Science Foundation of China (Grants 11672268, 11621062, and 91748209)the Zhejiang Provincial Natural Science Foundation of China (Grant LR16A020001)the Fundamental Research Funds for Central Universities of China (Grant 2017FZA4029).
文摘The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexagonally packed and interconnected via cross-linking proteins including α-actinin, filamin, and fascin. As pushing against the plasma membrane and/or external barriers, the actin bundles in filopodial protrusion inevitably encounter a compressive load. The bending stiffness and buckling stability of actin bundles are therefore important in determining the filopodia architecture and subsequent cell morphology. In this work, we employ a coarse-grained molecular dynamics model to investigate the buckling behaviors of cross-linked actin bundles under compression, which explicitly accounts for the properties of constituent filaments and the mechanical descriptions of cross-linkers. The bending stiffness of actin bundles exhibits a generic size effect depending on the number of filaments in the bundles, explicitly depending on the degree of inter-filament coupling. The distinct buckling modes are analyzed for bundles with different coupling states and strengths of cross-linkers. This study could clarify the stability and buckling mechanisms of parallelly packed actin bundles and the structure-function relations of mechanical components in filopodial protrusion.
基金the National Natural Science Foundation of China(Nos.11772293 and12072312)Zhejiang Science and Technology Project(No.2019C03129)。
文摘An actual ecological predator-prey system often undergoes random environmental mutations owing to the impact of natural disasters and man-made destruction, which may destroy the balance between the species. In this paper,the stochastic dynamics of the nonlinear predator-prey system considering random environmental mutations is investigated, and a feedback control strategy is proposed to reshape the response of the predator-prey system against random abrupt environmental mutations. A delayed Markov jump system(MJS) is established to model such a predator-prey system. A novel first integral is constructed which leads to better approximation solutions of the ecosystem. Then, by applying the stochastic averaging method based on this novel first integral, the stochastic response of the predator-prey system is investigated, and an analytical feedback control is designed to reshape the response of the ecosystem from the disturbed state back to the undisturbed one.Numerical simulations finally illustrate the accuracy and effectiveness of the proposed procedure.
基金This work is supported by the National Natural Science Foundation of China （nos. 11525210, 11621062, and 91748209） and the Fundamental Research Funds for the Central Universities.
文摘Developing robotic manipulators capable of performing effective physical interac- tion tasks is a challenging topic. In this study, we design a soft robotic arm （SRA） with multiple degrees of freedom inspired by the flexible structures and the unique motion mechanism of the octopus arm. The SRA is fabricated with elastomeric materials, which consists of four series of integrated pneumatic chambers that play similar roles as the muscles in the octopus arm can achieve large bending in various directions with variable stiffness. This SRA displays specified movements via controlling pressure and selecting channels. Moreover, utilizing parallel control, the SRA demonstrates complicated three-dimensional motions. The force response and motion of the SRA are determined both experimentally and computationally. The applications of the present SRA include tightly coiling around the objects because of its large bending deformation （nearly 360°）, grasping multiple objects, and adjusting the grabbing mode in accordance with the shape of objects.
基金This work acknowledges the supports from the following programs:National Key R&D Program of China(2017YFA0701100)National Natural Science Foundation of China(11572280,11822207,U161320211321202 and 11432012)+3 种基金National Basic Research Program of China(Grant No.2015CB057301)China Association for Science and Technology(Young Elite Scientist Sponsorship Program No.YESS20150004)Zhejiang Provincial Natural Science Foundation of China(R18A020004)Fund of State Key Laboratory of Fluid Power and Mechatronic Systems,Zhejiang University,and Dr.Li Dak Sum&Yip Yio Chin Fund for Stem Cell and Regenerative Medicine.
文摘Natural muscle provides excellent motilities for animals.As the basic unit of the muscle system,the skeletal muscle fibers function as a soft linear actuator.Inspired by the muscle fibers,researchers have developed various soft active devices with linear actuation.This paper reviews several soft linear actu ators,such as the dielec trie elastomer,t hermal responsive hydrogels,pneumatic artificial muscle,and conducting polymers.The actuation mechanisms and performances of these soft linear actuators are summarized.Based on the dielectric elastomer,we propose a design of a hybrid system with linear actuation,driven by both the electric motor and dielectric elasto mer cone.The elec tromechanical behaviors of the dielec trie elastomer cone have been investigated in both experiment and finite element analysis.This work may guide the further design of soft actuators and robots.
基金supported by the National Natural Science Foundation of China (Nos.11672265,11621062,and 11202182)the Fundamental Research Funds for the Central Universities (Nos.2016QNA4026 and 2016XZZX001-05)the open foundation of Zhejiang Provincial Top Key Discipline of Mechanical Engineering
文摘We study electromechanical fields near the interface between a circular piezoelectric semiconductor cylinder and another piezoelectric semiconductor in which it is embedded. The cylinder is p-doped. The surrounding material is n-doped. The phenomenological theory of piezoelectric semiconductors consisting of the equations of piezoelectricity and the conservation of charge for holes and electrons is used. The theory is linearized for small carrier concentration perturbations. An analytical solution is obtained, showing the formation of a PN junction near the interface. Various electromechanical fields associated with the junction are calculated. The effects of a few physical parameters are examined.
基金support received from the National Natural Science Foundation of China (11472243, 11302189, 11321202)the Doctoral Fund of Ministry of Education of China (20130101120175)
文摘The effect of piezoelectricity on phonon properties and thermal conductivity of gallium nitride （GaN） nanofilms is theoretically investigated. The elasticity model is utilized to derive the phonon properties in spatially confined GaN nanofilms. The piezoelectric constitutive relation in GaN nanofilms is taken into account in calculating the phonon dispersion relation. The modified phonon group velocity and phonon density of state as well as the phonon thermal conductivity are also obtained due to the contribution of piezoelectricity. Theoretical results show that the piezoelectricity in GaN nanofilms can change significantly the phonon properties such as the phonon group velocity and density of states, resulting in the variation of the phonon thermal conductivity of GaN nanofilms remarkably. Moreover, the piezoelectricity of GaN can modify the dependence of thermal conductivity on the geometrical size and temperature. These results can be useful in modeling the thermal performance in the active region of GaN-based electronic devices.
基金The work at Harvard University,USA was supported by National Science Foundation(NSF)Materials Research Science and Engineering Centers(MRSEC)(DMR-2011754)X.Yang was a visiting student at Harvard University supported by the China Scholarship Council.J.Steck acknowledges support from the NSF Graduate Research Fellowship(DGE1745303).
文摘A plastic may degrade in response to a trigger.The kinetics of degradation have long been characterized by the loss of weight and strength over time.These methods of gross characterization,however,are misleading when plastic degrades heterogeneously.Here,we study heterogeneous degradation in an extreme form:the growth of a crack under the combined action of chemistry and mechanics.An applied load opens the crack,exposes the crack front to chemical attack,and causes the crack to outrun gross degradation.We studied the crack growth in polylactic acid(PLA),a polyester in which ester bonds break by hydrolysis.We cut a crack in a PLA film using scissors,tore it using an apparatus,and recorded the crack growth using a camera through a microscope.In our testing range,the crack velocity was insensitive to load but was sensitive to humidity and pH.These findings will aid the development of degradable plastics for healthcare and sustainability.
基金This work was supported by Key Research and Development Program of Guangdong Province(2019B030335001)the Natural Science Foundation of China(31871070,82090031)+4 种基金Key R&D Program of Zhejiang Province(2020C03009)Science and Technology Program of Guangdong(2018B030334001)Funds for Creative Research Groups of China from the National Natural Science Foundation of China(81521062)Non-Profit Central Research Institute Fund of the Chinese Academy of Medical Sciences(2019PT310023)CAMS Innovation Fund for Medical Sciences(2019-I2M-5-057).
文摘Parkinson’s disease(PD)is the second most common and fastest-growing neurodegenerative disorder.In recent years,it has been recognized that neurotransmitters other than dopamine and neuronal systems outside the basal ganglia are also related to PD pathogenesis.However,little is known about whether and how the caudal zona incerta(ZIc)regulates parkinsonian motor symptoms.Here,we showed that specific glutamatergic but not GABAergic ZIc^(VgluT2) neurons regulated these symptoms.ZIc^(VgluT2) neuronal activation induced time-locked parkinsonian motor symptoms.In mouse models of PD,the ZIc^(VgluT2) neurons were hyperactive and inhibition of their activity ameliorated the motor deficits.ZIc^(VgluT2) neurons monosynaptically projected to the substantia nigra pars reticulata.Incerta-nigral circuit activation induced parkinsonian motor symptoms.Together,our findings provide a direct link between the ZIc,its glutamatergic neurons,and parkinsonian motor symptoms for the first time,help to better understand the mechanisms of PD,and supply a new important potential therapeutic target for PD.
基金Project supported by the National Natural Science Foundation of China(Nos.11532001and 11621062)the Fundamental Research Funds for the Central Universities of China(No.2016XZZX001-05)
文摘The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is derived with the consideration of both the nonlocal and the active control effects. The numerical results show that the nonlocal effect can effectively enhance the frequency in the middle part of the dispersion curve.When the nonlocal effect is strong enough, zero and negative group velocities will be evoked at different points along the dispersion curve, which will provide different ways of transporting energy including the forward-propagation, localization, and backwardpropagation of wavepackets related to the phase velocity. Both the nonlinear effect and the active control can enhance the frequency, but neither of them is able to produce zero or negative group velocities. Specifically, the active control enhances the frequency of the dispersion curve including the point at which the reduced wave number equals zero, and therefore gives birth to a nonzero cutoff frequency and a band gap in the low frequency range. With a combinational adjustment of all these effects, the wave propagation behaviors can be comprehensively controlled, and energy transferring can be readily manipulated in various ways.
