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Based on the surface elasticity theory established by Gurtin and Murdoch, one-dimensional (1D) multi-field coupling model incorporating surface effects for piezoelectric semiconductor (PS) nanostructures is developed, in which the surface effect is treated as a non-classical mechanical boundary condition. With the derived equations, we conduct a theoretical analysis of static bending and free vibration of a simply supported n-type PS beam with open-circuit and electrically isolated boundary conditions at two ends. Numerical results show that the surface effect can stiffen the PS beam, and thus enhance its natural frequencies. Due to the influence of surface effects, the physical quantities such as the effective rigidity and natural frequencies of the PS beam exhibit a considerably significant size-dependent property when the radius R of the PS beam’s cross-section is smaller than 400 nm. For the free vibration of the PS beam, the motion of electrons causes a damping effect. Both the surface effect and initial concentration of electrons have an effect on the quasi-damping ratio of the PS beam. The surface effect tends to enhance the damping effect.

A novel ceramic sensing material, orthorhombic molybdenum trioxide (a-MoO3) nanobelts, was successfully prepared through a simple hydrothermal strategy. And its crystalline phase and microstructures were characterized via X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The results indicate that the size of the a-MoO3 nanobeltsis 180-250 nm in width and several microns in length. Gas sensing performances of the as-synthesized a-MoO3 nanobelts towards acetone vapor which was a representative VOCs in asphalt were investigated. The a-MoO3 nanobelts based gas sensor exhibits superior response at the optimum operating temperature of 300 °C for 200 ppm acetone vapor and excellent stability. The gas sensing mechanism for the a-MoO3 nanobelts to acetone vapor was also discussed.

The stability, dispersion, and rheological properties of clay suspensions are important in the process of drilling. Organic clays were obtained traditionally by cation exchange, which is thermally unstable due to weak electrostatic interaction between the cationic surfactant and clay minerals. The purpose of the present study was to yield a stable and well dispersed organic bentonite (OBent) as a rheological additive for oil-based drilling mud. The co-modified method was used to modify bentonite by a cationic surfactant (cetyltrimethoxyammonium bromide: CTAB) and a silane coupling agent (hexadecyltrimethoxysilane: HDTMS). Firstly, the basal spacing of bentonite was enlarged by intercalation of CTAB, and the thermal stability of bentonite was improved by covalent bonds of HDTMS onto the bentonite platelets. The as-prepared OBent was characterized by infrared analysis, X-ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. The hydrophobicity, solubility, viscosity, and tribological performance of the OBent were also recorded. The test results showed that the hydrophobicity of the co-modified bentonite was improved significantly, and was greater than that of bentonite modified with single surfactant CTAB or HDTMS. The bentonite modified by the surfactant together with the silane coupling agent had stable rheology and a lower coefficient of friction than the single surfactant-modified bentonite because more HDTMS entered into the interlayer spaces and formed chemical bonds at the inner surface of platelets.

We study the torsion of a composite rod of a nonpiezoelectric semiconductor core coated within a piezoelectric dielectric shell. A one-dimensional model is established using the macroscopic theory ...

In this study, water soluble CuO nanostructures having nanobelt, nanorod, or spindle morphologies were synthesized using aqueous solutions of Cu(NO3)2·3H2O and NaOH by adjusting the type of surface modifier and reaction temperature. The effect of morphologies of these various CuO nanostructures as water-based lubricant additives on tribological properties was evaluated on a UMT-2 micro-friction tester, and the mechanisms underlying these properties are discussed. The three different morphologies of CuO nanostructures exhibited excellent friction-reducing and anti-wear properties. Tribological mechanisms differed in the initial stage of frictional interactions, but in the stable stage, a tribochemical reaction film and adsorbed lubricious film on the rubbing surfaces played important roles in hindering direct contact between friction pairs, leading to improved tribological properties.

Interface engineering by local polarization using piezoelectric1–4, pyroelectric5,6 and ferroelectric7–9 effects has attracted considerable attention as a promising approach for tunable electronics/optoelectronics, human–machine interfacing and artificial intelligence. However, this approach has mainly been applied to non-centrosymmetric semiconductors, such as wurtzite-structured ZnO and GaN, limiting its practical applications. Here we demonstrate an electronic regulation mechanism, the flexoelectronics, which is applicable to any semiconductor type, expanding flexoelectricity10–13 to conventional semiconductors such as Si, Ge and GaAs. The inner-crystal polarization potential generated by the flexoelectric field serving as a ‘gate’ can be used to modulate the metal–semiconductor interface Schottky barrier and further tune charge-carrier transport. We observe a giant flexoelectronic effect in bulk centrosymmetric semiconductors of Si, TiO2 and Nb–SrTiO3 with high strain sensitivity (>2,650), largely outperforming state-of-the-art Si-nanowire strain sensors and even piezoresistive, piezoelectric and ferroelectric nanodevices14. The effect can be used to mechanically switch the electronics in the nanoscale with fast response (

We study the electrical response of a multiferroic composite semiconductor fiber consisting of a piezoelectric semiconductor layer and two piezomagnetic layers under a transverse magnetic field applied locally to a finite part of the fiber. The phenomenological theory of piezomagnetic-piezoelectric semiconductors is employed. A one-dimensional model is derived for magnetically induced extension of the fiber. For open-circuit boundary conditions at the two ends of the fiber, an analytical solution is obtained from the model linearized for small carrier perturbations. The solution shows a local electric polarization and a pair of local electric potential barrier-well. When the two ends of the fiber are under a voltage, a nonlinear numerical solution shows that the potential barrier and well forbid the passage of currents when the voltage is low. The results have potential applications in piezotronic devices when magnetic fields are involved for manipulating the devices or sensing and transduction.

We examine the effects of a uniform temperature change on PN junctions in piezoelectric semiconductor fibers. A one-dimensional model for thermally induced extensional deformation of the fibers derived previously from the macroscopic theory of thermopiezoelectric semiconductors is employed. With the linearized model, we present the analytical expressions of the built-in potential, carrier distribution, electric field, and polarization field in piezoelectric semiconductor PN junctions. A combined analytical and numerical analysis is performed on the built-in electromechanical fields in the junctions and their current–voltage relations. Numerical results show that homogeneous junctions have relatively good temperature stability, but heterogeneous junctions are sensitive to a temperature change that may be explored for thermally manipulating piezotronic devices. The difference between the temperature behaviors of the two types of junctions is determined to be due to the net amount of effective polarization charges at the junctions through pyroelectric and combined thermoelastic-piezoelectric couplings.

The road-base usually deteriorate during service time due to factors such as cyclical traffic loads and road-base fouling. Currently the monitoring method for road-base quality is quite limited. This paper proposes a real-time Monitoring method for Road-Base Quality (MRBQ) based on a soil dynamic model and piezoelectric sensors buried in road-base. The soil dynamic model was extended with a piezoelectric equation to calculate the voltage in the road-base generated by a moving traffic load. Then, a model test was conducted to measure the output voltage of the piezoelectric sensors buried in the road-base. Finally, the road-base modulus was back-calculated through the soil dynamic model with the measured voltage. The back-calculated modulus was compared with the modulus measured by resonance column test (RCT) to validate this method. The unique relationship between the peak voltage and the road-base modulus at various depths was identified for different traffic load amplitudes and speeds, and the feasibility and accuracy of the MRBQ was demonstrated. This study reveals that the sensitivity of the piezoelectric sensors can reach 2 V/MPa, and the error to measure the road-base modulus is less than 20%. The proposed MRBQ demonstrates a good application potential in health monitoring of transportation facilities.

In order to overcome the mismatching between traditional additives and DLC coatings in solid-liquid lubricating system. Cu nanoparticles modified with diisooctyl dithiophosphoric acid (NPCuDDP) were prepared and used as nano-additives in DLC/PAO solid-liquid lubricating systems. Four kinds of DLC coatings including amorphous carbon (a-C) and amorphous carbon doped with Si (a-C(Si)), Al (a-C(Al)) and H (a-C(H)) respectively, with a hardness range from 22 GPa to 7 GPa were used to study the tribological mechanism and adaptability of NPCuDDP to the hardness and composition of DLC coatings. It was found that NPCuDDP reduced the COF of DLC coatings/PAO systems by 19%–22% regardless of their hardness and composition and made the wear rate of all DLC coatings decrease by 2–3 orders of magnitude. While the composite of tribofilm was decided by the doped elements in DLC coatings. The doped element H inhibited the oxidation of copper in tribofilm, and led to the lowest wear rate of a-C(H) coating. The doped element Al in a-C(Al) facilitated the enrichment of phosphates on friction surface. The hardness rather than composition of DLC coatings determines whether traditional additive ZDDP can form tribofilm. ZDDP can only form Zinc polyphosphate tribofilm on the steel balls rubbed with a-C, a-C(Si) and a-C(Al) coatings whose hardness was over 12 GPa. The friction coefficient of the system increases greatly because of the high strength of ZDDP tribofilm. The high activity of soft metal nano-particle in NPCuDDP urged the formation of tribofilm on friction surface easily and produced a significant antifriction and antiwear effect, and is expected to replace traditional small molecule additives as the high-efficiency special lubricating oil additives for DLC coatings solid-liquid lubrication system.

We study the effects of a uniform temperature change on the electromechanical fields associated with the extensional deformation of a piezoelectric semiconductor fiber. The macroscopic theory of thermo-piezoelectric semiconductors is used. Based on the three-dimensional equations, we develop a one-dimensional model for thin piezoelectric semiconductor fibers incorporating thermoelasticity, piezoelectricity, and pyroelectricity. Through a theoretical analysis, it is shown that under a temperature change the carriers in the fiber redistribute themselves under the electric field produced through thermoelastic, pyroelectric and piezoelectric effects. This phenomenon of thermally induced redistribution of charge carriers may be called thermo-piezotronic effect. It suggests the possibility of sensing or transduction between a temperature change and electric currents.

如今新兴的智能化时代比以往任何时候都更需要性能优越的材料和结构来设计更灵活、更主动、更自动化的机器和系统,以应对越来越复杂的环境。本实验室力图探求智能材料与结构在实验或计算中观测到的力学现象(如自由振动、波传播以及结构失稳等)或是多场耦合行为背后的机理,从而为先进功能设备、机械以及机器人的创新发展提供参考。最终,开发具有卓越性能的新型智能多功能器件,以满足各种实验室、工业甚至社会应用的特殊或一般要求。 1. 智能结构的振动与失稳分析;2. 软材料的设计与制备;3. 声子晶体和超材料中弹性波的调控;4. 智能材料和结构中的多场耦合行为分析;5. 压电、多铁性以及压电电子学器件的研发;6. 多轴力/力矩智能传感器的设计。 虽然对智能材料和结构的研究已有近40 年的历史,且其在许多现代技术和工程领域中已有了成功的应用,但是即将到来的智能化时代对“智能力学”的需求将是无穷无尽的。如果说传感器和驱动器是智能化时代的基础,那么智能材料和结构就是这些基本设备的核心。新型多功能材料的开发显然为智能材料和结构力学带来了新的生机和活力。此外,拓扑物理学等新的科学概念也将为智能材料和结构的研究开辟新的方向。本实验室将继续为基础科学、技术发展以及智能材料和结构的实际应用做出贡献。

Piezoelectric semiconductors (PSs), possessing the characteristic of deformation-polarization-carrier multi-field coupling, have been widely used in energy harvesters, field-effect transistors, and other intelligent devices. It is very important to investigate the effect of the polarization field only induced by flexoelectricity on piezotronic behaviors of PS nanostructures. We propose a sandwich-type PS composite beam with bending deformation, and develop the one-dimensional model for PS composite beams with flexoelectricity. Through introducing the average electric field in the thickness, we can get rid of the contribution from piezoelectricity to the total induced polarization, as a result, the individual effect of flexoelectricity on the macroscopic multi-field coupling behaviors of the bending composite beam can be evaluated.

Terahertz electromagnetic waves have many important applications in the fields of material characterization, optical scanning imaging, security, biomedicine and communication. However, the research on terahertz elastic waves is quite limited. Based on the classical Love’s rod theory, we develop the one-dimensional theory for piezoelectric semiconductor rod by taking the lateral inertial effect into account. Using the derived model, we conduct an analysis of elastic longitudinal wave propagating in an in infinite piezoelectric semiconductor rod at terahertz frequencies, and investigate the effect of the rod’s radius and the initial electron concentration on phase speed and group speed. The numerical results show that within the terahertz region (THz) the lateral inertial effect plays a dominant role in wave propagation properties.

Piezoelectric semiconductors (PSs) have great potential applications in future multifunctional devices. The interaction among deformation, polarization, and carrier in PSs under an external load leads to a variety of innovative electronic, mechanical, and optical behaviors. Studying multi-field coupling mechanical behaviors of PSs plays a fundamental role in PS devices. However, the partial differential equations (PDEs) describing PSs are nonlinear. This brings rather a mathematical challenge to analysis of PSs. In this work, we propose a machine-learning-based approach to solving multi-field coupling problems of piezoelectric semiconductors. Based on the linear analytical solution, the physics-informed neural networks (PINNs) is trained to obtain the data-driven solutions for a static axial extensional PS rod.

Highly infiltrative and invasive glioma cells obscure the boundary between tumor and normal brain tissue, making it extremely difficult to precisely diagnose and completely remove. The combination of multimodal imaging with effective treatments to diagnose precisely and guide surgery and therapy accurately is desperately needed for glioma in the brain. Here, we report a biomimetic catalase-integrated-albumin phototheranostic nanoprobe (ICG/AuNR@BCNP) to realize multimodal imaging, amplify phototherapy, and guide surgery for glioma after penetrating the blood-brain barrier, accumulating into deep-seated glioma via albumin-binding protein mediated transportation. The phototheranostic nanoprobe enabled fluorescence, photoacoustic, and infrared thermal imaging with desirable detecting depth and high signal-to-background ratio for clearly differentiating brain tumors from surrounding tissues. Meanwhile, the nanoprobe could effectively induce local hyperthermia and promote the level of singlet oxygen based on alleviated hypoxic glioma microenvironment by decomposing endogenous hydrogen peroxide to oxygen to amplify phototherapy. Thus, significant inhibition of glioma growth, extended survival time, alleviated tumor hypoxia, improved apoptosis, and antiangiogenesis effects were exhibited in several animal models including the periphery and the brain through intravenous or intratumoral injection, meanwhile with low toxicity to normal tissue. The phototherapy was also guided by the assistance of external bioluminescence, magnetic resonance, and positron emission tomography imaging. Moreover, the nanoprobe could accurately guide the glioma resection. These results suggest that the phototheranostic nanoprobe is a promising nanoplatform specifically for glioma to achieve multimodal diagnosis, effective phototherapy, and accurate imaging-guided surgery.

The piezoresistive effect has shown a remarkable potential for mechanical sensor applications and been sought for its excellent performance. A great attention was paid to the giant piezoresistive effect and sensitivity delivered by silicon-based nanostructures. However, low thermal stability and complicated fabrication process hinder their practical applications. To overcome these issues and enhance the functionalities, we envision the substantial piezopotential in a zinc oxide (ZnO)/muscovite (mica) heteroepitaxy system based on theoretical consideration and realize it in practice. High piezoresistive effect with giant change of resistivity (-80 to 240%) and large gauge factor (>1000) are demonstrated through mechanical bending. The detailed features of heteroepitaxy, electrical transport, and strain are probed to understand the mechanism of such a giant resistivity change. In addition, a bending model is established to reveal the distribution of strain. Finally, we demonstrate a flex sensor featuring high sensitivity, optical transparency, and two-segment sensing with a great potential toward practical applications. Such an oxide heteroepitaxy exhibits excellent piezoresistive properties and mechanical flexibility. In the near future, the importance of flex sensors will emerge because of the precise control in the automation industries, and our results lead to a new design in the field of flex sensors.

Efficient and sustainable use of water-based lubricants is essential for energy efficiency. Therefore, the use of water-lubricated mechanical systems instead of conventional oil lubricants is extremely attractive from the viewpoint of resource conservation. In this study, water-soluble Cu nanoparticles of size approximately 3 nm were prepared at room temperature (around 25 °C) via in-situ surface modification. The tribological behavior of the as-synthesized Cu nanoparticles as an additive in distilled water was evaluated using a universal micro-tribotester. The results show that the as-synthesized Cu nanoparticles, as a water-based lubricant additive, can significantly improve the tribological properties of distilled water. In particular, the lowest friction coefficient of 0.06 was obtained via lubrication with a concentration of 0.6 wt% of Cu nanoparticles in distilled water, which is a reduction of 80.6% compared with that obtained via lubrication with distilled water alone. It is considered that some Cu nanoparticles entered the contact area of the friction pairs to form a complex lubricating film and prevent direct contact of the friction pairs. Furthermore, some Cu nanoparticles in the solution accelerate the heat transfer process, which also results in good tribological properties.

Motivated by the growth of MnAs/GaAs thin films in many experimental researches, we investigate the electronic and magnetic properties of bulk, (001) surfaces and (001) interfaces for zinc blende MnAs by means of first-principle calculations. It is confirmed that zinc blende MnAs is a nearly half-metallic ferromagnet with 4.00 μB magnetic moment. The calculated density of states show that the half-metallicity exists in As-terminated (001) surface while it is lost in Mn-terminated (001) surface. For the (001) interfaces of MnAs with semiconductor GaAs, it is found that As-Ga and Mn-As interfaces not only have higher spin polarization but also are more stable among the four considered interfaces. Our results would be helpful to grow stable and high polarized thin films or multilayers for the practical applications of spintronic devices.

Ocean waves are one of the most power dense energy sources in the environment. Triboelectric nanogenerators (TENGs) have been demonstrated to effectively harvest mechanical energy carried by low frequency, random/irregular actuation, such as from ocean waves. In this work, a novel design of triboelectric nanogenerator based on the Pelamis snake energy harvester is presented. The sea snake based TENG, with its lightweight structure, was able to harvest energy effectively at low amplitude ocean wave by utilizing charged polytetrafluroethylene balls that would roll due to the wave's curvature. With the integration of springs to connect different segments, the segments are able to bend easily, allowing the enclosed balls to move faster, producing higher output power. The design of an air gap structure allows each segments of the sea snake based TENG to minimize electrostatic induction from ions in sea water, and solve the effect of dielectric shielding from the water on the device performance, as the water, if it is close to the TENG's electrodes, has a detrimental effect causing an increase of the TENG's internal capacitance, which would result in a low voltage with the same amount of charge being transformed. Thus, this illustrates the importance of the air gap structure to minimize low voltage due to high internal capacitance. This further shows the sea snake based triboelectric nanogenerator could be used in actual ocean conditions, such as in high salinity water environment. The added tampered spring to replace the air gap was able to allow the balls on the TENG to move more quickly, as it increased the rotational angle, and the TENG has a maximum power density of 3 W/m3 under actuation. Due to the minimization of dielectric shielding of device performance, the sea snake TENG exhibits a high voltage in simulated water wave conditions.

A theoretical model is developed for predicting both conduction and diffusion in thin-film ionic conductors or cables. With the linearized Poisson-Nernst-Planck (PNP) theory, the two-dimensional (2D) equations for thin ionic conductor films are obtained from the three-dimensional (3D) equations by power series expansions in the film thickness coordinate, retaining the lower-order equations. The thin-film equations for ionic conductors are combined with similar equations for one thin dielectric film to derive the 2D equations of thin sandwich films composed of a dielectric layer and two ionic conductor layers. A sandwich film in the literature, as an ionic cable, is analyzed as an example of the equations obtained in this paper. The numerical results show the effect of diffusion in addition to the conduction treated in the literature. The obtained theoretical model including both conduction and diffusion phenomena can be used to investigate the performance of ionic-conductor devices with any frequency.

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.

In this study, a sulphur and nitrogen dual-doped carbon catalyst was prepared via an easy route with p-phenyldiamine and (NH4)2S2O8 as the nitrogen and sulphur source, respectively. The obtained catalyst displayed efficient acetylene conversion for acetylene hydrochlorination, and the presence of sulphur enhanced the catalytic activity of the nitrogen-doped carbon catalyst. These catalysts show that sulphur and nitrogen have a synergistic effect for acetylene hydrochlorination. Furthermore, because of the addition of different sulphur contents, the pyrrolic N content causes certain changes in the catalysts, resulting in differences in the catalytic activity. Theoretical investigations reveal that the adsorption ability of C2H2 was enhanced by the doping of the S and N-doped carbon catalyst. This is an environmentally friendly catalyst with a broad development prospect and is cheap and easy to obtain.

Pathological changes in a diseased site are often accompanied by abnormal activities of various biomolecules in and around the involved cells. Identifying the location and expression levels of these biomolecules could enable early-stage diagnosis of the related disease, the design of an appropriate treatment strategy, and the accurate assessment of the treatment outcomes. Over the past two decades, a great diversity of peptide-based nanoprobes (PBNs) have been developed, aiming to improve the in vitro and in vivo performances of water-soluble molecular probes through engineering of their primary chemical structures as well as the physicochemical properties of their resultant assemblies. In this review, we introduce strategies and approaches adopted for the identification of functional peptides in the context of molecular imaging and disease diagnostics, and then focus our discussion on the design and construction of PBNs capable of navigating through physiological barriers for targeted delivery and improved specificity and sensitivity in recognizing target biomolecules. We highlight the biological and structural roles that low-molecular-weight peptides play in PBN design and provide our perspectives on the future development of PBNs for clinical translation.

Saturated column experiments were conducted to systematically examine transport of graphene oxide nanoparticles (GONPs) in sand porous media at different solution ionic strengths (ISs) with different flow velocities. Results show that deposition of GONPs increase with decreasing IS. However, the Derjaguin–Landau–Verwey–Overbeek (DLVO) interaction energy calculations using a surface element integration technique show that the energy barrier increases with increasing IS for the sheet-shaped colloids interacting with a planar sand surface. In contrast, the presence of nanoscale protruding asperities (NPAs) can cause a decrease in the energy barrier with increasing IS, which facilitates the attachment in primary minima at higher IS. At a given IS, increasing flow velocity increases attachment efficiency on the rough sand surfaces. Torque analysis shows that the maximum hydrodynamic torques are smaller than the adhesive torques, even for GONPs located on the NPAs where the adhesions are the lowest. Consequently, the attachment efficiency cannot be reduced by increasing flow velocity. Additional column experiments confirm that deposited GONPs cannot be detached by increasing flow velocity. Conversely, increase of flow velocity may enhance approaching of GONPs in low-flow regions such as concave areas of sand surfaces and subsequent attachment. Although it has been recognized in the literature that the presence of NPAs can cause decrease of attachment efficiency with increasing flow velocity for spherical colloids under both unfavorable and favorable chemical conditions, our results highlight a different role of surface roughness in attachment and detachment of sheet-shaped colloids under unfavorable conditions.

Polystyrene nanoplastics (PS-NPs) are known to impair the function of the digestive system, intestinal flora, immune system, and nervous system of marine organisms. We tested whether PS-NPs influence viral infection of orange-spotted grouper (Epinephelus coioides). We found that grouper spleen (GS) cells took up PS-NPs at exposure concentrations of 5, 50, and 500 μg/mL and experienced cytotoxicity at 50 and 500 μg/mL concentrations. At 12 h after exposure to 50 μg/mL of PS-NPs, the replication of Singapore grouper iridovirus (SGIV) and red-spotted grouper nervous necrosis virus (RGNNV) increased in GS cells after their invasion. Juvenile fish exposed to 300 and 3000 μg/L of PS-NPs for 7 d showed PS-NPs uptake to the spleen and vacuole formation in brain tissue. Moreover, PS-NPs exposure accelerated SGIV replication in the spleen and RGNNV replication in the brain. PS-NP exposure also decreased the expression of toll-like receptor genes and interferon-related genes before and after virus invasion in vitro and in vivo, thus reducing the resistance of cells and tissues to viral replication. This is the first report that PS-NPs have toxic effects on GS cells and spleen and brain tissues, and it provides new insights into assessing the impact of PS-NPs on marine fish.

Based on three-dimensional equations of piezoelectric semiconductors, we take flexoelectricity into consideration to develop a deformation–polarization–carrier coupling analysis model for the bending of a piezoelectric semiconductor (PS) composite bilayer, which is composed of a piezoelectric semiconductor layer and an elastic layer. Using the derived equations, we investigate the macroscopic responses, such as the distribution of electromechanical field and carrier concentration, of the PS composite bilayer with bending deformation. The induced polarization in the PS composite bilayer exhibits an apparent size-dependent property due to the flexoelectric coupling effect, and thus has a remarkable influence on the piezotronic effect in the PS composite bilayer with nano-thickness. The obtained results are useful for designing novel piezoelectric semiconductor devices.

We have reported the formation of fluorescent CdSe/ZnS quantum dots (QDs) incorporated poly (styrene-co-maleic anhydride) spheres in nanoscale range with a simple emulsification solvent evaporation strategy. The influence parameters on the size and internal structure of the composite nanospheres, such as copolmer/QDs mass ratio and volume ratio of water/chloroform were systematically investigated. Our obtained QDs incorporated polymer nanospheres were suitable for some immunoassays which strongly required nano-sized fluorescent labels, such as lateral flow immunoassays (LFIAs), in which “easily flowing chromatographically along the strip” was needed. Finally, carboxyl-functionalized nanospheres were used as fluorescent tags and imported into LFIA system to on-site high-sensitively assess the level of C-reaction protein (CRP). Within the range of high-sensitive detection (from 0.04 to 10.0 mg/L), nanosphere-based LFIA sensor exhibited linear detection of CRP (R2 = 0.9995) and a detection limit of 0.04 mg/L, which may be useful to improve the risk assessment of cardiovascular disease.

Piezoelectric semiconductors (PS) nanofibers, which simultaneously exhibit piezoelectricity and unique electric conductive behavior, have huge applications in sensors, energy harvesters, and piezoelectric field effect transistors. Electromechanical fields and charge carrier in PS nanofibers can be effectively controlled by a mechanical force. One-dimensional linear equations for PS nanofibers, which are suitable for small axial force and small electron concentration perturbation, are presented. Analytical expressions for the electromechanical fields and electron concentration in the fiber are obtained. Numerical results show that the electromechanical fields near the two ends are sensitive to the initial electron concentration and the applied axial force.

In this study, epoxy coatings were modified by adding various compositions of B4C particles. In order to achieve proper dispersion of particles in the epoxy coating and increasing chemical interactions between particles and polymeric coating, the surface of the B4C particles was treated with γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560). The surface modification and microstructure of B4C were characterized by Fourier transform infrared, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical impedance spectroscopy was also used to evaluate the impedance of coatings. The results revealed that the KH560 not only enhanced the interaction between B4C particles and epoxy resin but also exhibited a remarkable ability to improve the anticorrosion performance of epoxy resin. The epoxy coating with the 3 wt% B4C-KH560 particles exhibited the best anticorrosion performance, which can be attributed to the best uniform dispersion of the B4C-KH560 particles, and the particles effectively block the aggressive species (Cl−, O2, and H2O) from the coating.

Two-dimensional (2D) equations for multiferroic (MF) laminated plates with imperfect interfaces are established in this paper. The interface between two adjacent sublayers, which are not perfectly bonded together, is modeled as a general spring-type layer. The mechanical displacements, and the electric and magnetic potentials of the two adjacent layers are assumed to be discontinuous at the interface. As an example, the influences of imperfect interfaces on the magnetoelectric (ME) coupling effects in an MF sandwich plate are investigated with the established 2D governing equations. Numerical results show that the imperfect interfaces have a significant impact on the ME coupling effects in MF laminated structures.

We theoretically study the behaviors of a piezoelectric semiconductor (PS) fiber in the extensional deformation resulted from the two local thermal loads using the multi-field coupling theory for thermo-piezoelectric semiconductor. With the linearized method, the analytical results are obtained for small temperature changes. For large temperature changes, the linearized method is not valid. In this case, we conduct a nonlinear analysis by COMSOL. The numerical results show that the potential barrier and well produced by the temperature changes through a series of coupling effects could be used to manipulate the forward/reverse currents in the fiber simultaneously.

We study the extension of a piezoelectric semiconductor (PS) fiber containing a PN junction, focusing on the effective polarization charges which are fundamental to piezotronics. A one-dimensional model derived previously from the macroscopic theory of PSs is used for a linear theoretical and nonlinear numerical analysis by COMSOL. Both homogeneous and heterogeneous junctions are studied. In addition to the built-in electric potential and field as well as I-V curve, distributed effective polarization charge along the fiber and concentrated effective polarization charge on the junction interface are calculated and examined.

An adaptive iterative learning control (AILC) strategy is presented for a class of nonlinear pure-feedback systems with initial state error using fuzzy logic systems (FLS) to solve the problem of non-uniform trajectory tracking. The proposed control scheme utilizes fuzzy logic system to learn the behavior of the unknown plant dynamics. Filtered signals are employed to circumvent algebraic loop problems encountered in the implementation of the existing controllers. Backstepping design technique is applied to deal with system dynamics. Based on the Lyapunov-like synthesis, we show that all signals in the closed-loop system remain bounded over a pre-specified time interval [0,T]. There even exist initial state errors, the norm of tracking error vector will asymptotically converge to a tunable residual set as iteration goes to infinity. A time-varying boundary layer is introduced to solve the problem of initial state error. A typical series is introduced in order to deal with the unknown bound of the approximation errors and complete the non-uniform trajectory tracking problem. Finally, the simulation example of one-link robot system shows the feasibility and effectiveness of the approach.

We theoretically study the electromechanical behaviors of a laminated thin-film piezoelectric semiconductor (PS) composite plate with flexural deformation. The nonlinear equations for drift currents of electrons and holes are linearized for a small carrier concentration perturbation. Following the structural theory systemized by R. D. Mindlin, a system of two-dimensional (2D) equations for the laminated thin-film PS plate, including the lowest order coupled extensional and flexural motion, are presented by expanding the displacement, potential, and the incremental concentration of electrons and holes as power series of the plate thickness. Based on the derived 2D equations, the analytical expressions of the electromechanical fields and distribution of electrons in the thin-film PS plate with an n-type ZnO layer subjected to a static bending are presented. The numerical results show that the electromechanical behaviors and piezotronic effects can be effectively controlled by the external applied force and initial concentration of carriers. The derived 2D equations and numerical results in this paper are helpful for developing piezotronic devices.

We present a one-dimensional model for a piezoelectric semiconductor (PS) rod with varying cross section subject to an axial loading. Using the linearized method, we obtain exact solutions for an n-type PS rod under static extension. Based on the obtained solutions, the effect of the initial concentration of electrons, the axial force, and the radius ratio of two cross sections at the two ends on the redistribution of electrons in the ZnO rod is investigated. Numerical results show that there are a larger variation of electrons near the two ends of the rod, and the piezotronic effect in the PS rod can be controlled through applying an axial force as well as changing the initial concentration of carriers and geometric shape of PS rods.

Silicon-based Schottky barrier diodes (SBDs), as a two-terminal circuit element, are widely used in modern industries due to its low cost and better compatibility with the complementary metal oxide semiconductor (CMOS) technology. Flexoelectricity resulting from strain gradient is a distinctive electromechanical coupling phenomenon compared to piezoelectricity resulting from strain. Flexoelectricity can exist in any dielectric due to the non-uniform strain breaking symmetry of materials. In this paper, we utilize the induced flexoelectric polarization to tune the behavior of a SBD made of metal and p-type Silicon. Making use of conductive atomic force microscopy (C-AFM), we measured current-voltage of the fabricated Si-based SBD under different tip forces. In order to conduct a quantitative study on the tuning effect of flexoelectricity on the performance of the fabricated Si-based SBD, we introduce an effective barrier height and provide a modified current equation according to the classical thermionic emission theory. The results show that flexoelectricity plays a significant role in dictating the Schottky barrier height, maximum rectified current (density), reverse saturation current (density), rectification ratio, and open voltage of the fabricated SBD. In addition, based on the Hertzian contact model and the measured data, the nonzero flexoelectric coefficients of the used p-type silicon are obtained.

As hypoxia plays a vital role in the angiogenic-osteogenic coupling, using proline hydroxylase inhibitors to manipulate hypoxia-inducible factors has become a strategy to improve the osteogenic properties of biomaterials. Dimethyloxallyl glycine (DMOG) is a 2-ketoglutarate analog, a small molecular compound that competes for 2-ketoglutaric acid to inhibit proline hydroxylase. In order to improve the osteogenic ability of calcined bone calcium (CBC), a new hypoxia-mimicking scaffold (DMOG/Collagen/CBC) was prepared by immersing it in the DMOG-Collagen solution, followed by freeze-drying. All coated CBC scaffolds retained the inherent natural porous architecture and showed excellent biocompatibility. A slow release of DMOG by the DMOG-loaded CBC scaffolds for up to one week was observed in in vitro experiments. Moreover, the DMOG/Collagen/CBC composite scaffold was found to significantly stimulate bone marrow stromal cells to express osteogenic and angiogenic genes in vitro. In addition, the osteogenic properties of three kinds of scaffolds, raw CBC, Collagen/CBC, and DMOG/Collagen/CBC, were evaluated by histology using the rabbit femoral condyle defect model. Histomorphometric analyses showed that the newly formed bone (BV/TV) in the DMOG/Collagen/CBC group was significantly higher than that of the Collagen/CBC group. However, immunostaining of CD31 and Runx2 expression between these two groups showed no significant difference at this time point. Our results indicate that DMOG-coated CBC can promote osteogenic differentiation and bone healing, and show potential for clinical application in bone tissue engineering.

This work was to reveal magnetic response to wear-resistance of polyetheretherketone/Cu nanowires composites under water lubrication condition. The tribological performance, the worn surfaces, especially the tribofilms’ nanostructures and nanomechanical properties with and without magnetic field were investigated. The results reveal that magnetic field can enhance materials transfer, quicken tribofilm formation, and alleviate the stress concentration of the tribofilm. And magnetic field improves the structures and properties of the tribofilm, endowing which with superior easy-to-shear character and wear-resistance ability. Moreover, magnetic field keeps an ordering molecular structure of the PEEK matrix when transformed onto the worn surface, making up the friction heat loss due to the absorption of the running water, and further promoting the tribo-chemical reaction and the tribofilm formation.

A novel hybrid materials Fe 3 O 4 nanoparticles supported by hexagonal boron nitride (h-BN) is successfully prepared via mussel-inspired chemistry of dopamine by hydrothermal synthesis method. The surface modification and microstructure of h-BN-Fe 3 O 4 are characterized by FT-IR, XRD, XPS, SEM and TEM. The nano-Fe 3 O 4 obtain well dispersion supported by h-BN layer platform, and the h-BN-Fe 3 O 4 hybrid materials exhibit a remarkable superiority in enhancing the anticorrosion performance of epoxy coatings. The lamellar structural h-BN and nano-Fe 3 O 4 provide a significant synergistic effect in anticorrosion performance for epoxy composite coatings. In addition, the anticorrosion mechanisms of h-BN-Fe 3 O 4 are tentatively discussed.

Membrane separation is an effective method for the removal of hazardous materials from wastewater. Halloysite nanotubes (HNTs) were functionalized with 3-aminopropyltriethoxysilane (APTES), and novel polyvinylidene fluoride (PVDF) nanofiltration membranes were prepared by blending with various concentrations of APTES grafted HNTs (A-HNTs). The morphology structure of the membranes were characterized by scanning electron microscope (SEM) and atomic force microscopy (AFM). The contact angle (CA), pure water flux (PWF) and antifouling capacity of membranes were investigated in detail. In addition, the separation performance of membranes were reflected by the removal of dye and heavy metal ions in simulated wastewater. The results revealed that the hydrophilicity of A-HNTs blended PVDF membrane (A-HNTs@PVDF) was enhanced significantly. Owing to the electrostatic interaction between membrane surface and dye molecules, the dye rejection ratio of 3% A-HNTs@PVDF membrane reached 94.9%. The heavy metal ions rejection ratio and adsorption capacity of membrane were also improved with the addition of A-HNTs. More importantly, A-HNTs@PVDF membrane exhibited excellent rejection stability and reuse performances after several times fouling and washing tests. It can be expected that the present work will provide insight into a new method for membrane modification in the field of wastewater treatment.

Tricalcium silicate (C3S) mineral was prepared by sol–gel method, using tetraethyl orthosilicate as silicon source, Ca(NO3)2·4H2O as calcium source, EtOH as cosolvent and saltpeter solution as catalyst. The percentage of f-CaO of C3S is less than 0.18 %. C3S samples were hydrated with a w/b ratio 20 at room temperature. SEM results show calcium silicate hydrate (C–S–H) is a tightly coupled laminated structure within hydration 12 h and grew acicular fiber at later ages. The mean C/S ratios of C–S–H remain around 1.55 at 28 days. Calcium hydroxide (CH) occurs the directional growth toward the (001) crystal plane. XRD results show the width of CH diffraction peak got broadened with the increase in hydration ages and the crystallinity of C3S has dropped. Bound water in C–S–H at different ages of hydration supports the assumption that the hydration rate of C3S at early stage is much faster than that at late ages.

The hybrid coatings based on graphene oxide–zirconia dioxide/epoxy (GO–ZrO 2 /EP) system were fabricated and applied for corrosion protection of metal substrate. First, GO–ZrO 2 hybrid was synthesized through two different silane coupling agents and the morphology and structure were confirmed by Field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. Then, GO–ZrO 2 was incorporated into EP to investigate the corrosion protection of metal substrate. Investigations revealed that the corrosion protective properties were significantly enhanced by the addition of GO–ZrO 2 to EP. The enhancement attributed to the sheet-like structure, uniform dispersion and exfoliation of GO–ZrO 2 hybrid within EP matrix, which effectively prevented the underlying metal substrate from corrosion attack.

Hexagonal boron nitride (h-BN) is modified by a simple and green method based on self-oxidation of dopamine and epoxy groups functionalized silane (KH560) grafting. The surface modification and microstructure of h-BN are characterized by Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The poly(dopamine) and epoxy groups not only increase the compatibility of the h-BN and enhance its interaction with epoxy matrix but also exhibit a remarkable superiority in enhancing the anticorrosion performance of epoxy coatings. In addition, the anticorrosion mechanisms of h-BN@PDA-KH560 are tentatively discussed. Copyright © 2016 John Wiley & Sons, Ltd.

Binding nanoparticles on complex structured materials surface is an important issue for nanotechnology, such as obtain an superwetting surface. To fabricate a highly nanoparticles decorated polymer membrane with superior surface wettability, a facile and environmentally method stills remains challenge. Taken advantage from the mussel-inspired method, we reported here that the TiO2 nanoparticles were directly anchored on the surface of poly(vinylidene fluoride) (PVDF) membrane, making the intrinsic hydrophobic polymer membrane become hydrophilic, what's more, the mussel inspired method was modified by introducing a silane coupling agent KH550, the ability to bind nanoparticles was retained and the as-prepared membrane turn from a common hydrophilic state to superhydrophilic state. Besides, the as-prepared superhydrophilic PVDF membrane could be applied on the separation of various kinds of surfactant stabilized oil-in-water emulsion with an ultrahigh efficiency nearly 99% and also shows durable oil resistance and antifouling performance, thus make the membrane easily to recycle. In addition, due to the universality of dopamine, this surface modification method should also be applicable on other organic–inorganic hybrid materials.

We made a theoretical study of the carrier distribution and electromechanical fields in a free piezoelectric semiconductor rod of crystals of class 6 mm. Simple analytical expressions for the carrier distribution, electric potential, electric field, electric displacement, mechanical displacement, stress, and strain were obtained from a 1D nonlinear model reduced from the 3D equations for piezoelectric semiconductors. The distribution and fields were found to be either symmetric or antisymmetric about the center of the rod. They are qualitatively the same for electrons and holes. Numerical calculations show that the carrier distribution and the fields are relatively strong near the ends of the rod than in its central part. They are sensitive to the value of the carrier density near the ends of the rod.

Dielectric elastomers (DEs) respond to applied electric voltage with a surprisingly large deformation, showing a promising capability to generate actuation in mimicking natural muscles. A theoretical foundation of the mechanics of DEs is of crucial importance in designing DE-based structures and devices. In this review, we survey some recent theoretical and numerical efforts in exploring several aspects of electroactive materials, with emphases on the governing equations of electromechanical coupling, constitutive laws, viscoelastic behaviors, electromechanical instability as well as actuation applications. An overview of analytical models is provided based on the representative approach of non-equilibrium thermodynamics, with computational analyses being required in more generalized situations such as irregular shape, complex configuration, and time-dependent deformation. Theoretical efforts have been devoted to enhancing the working limits of DE actuators by avoiding electromechanical instability as well as electric breakdown, and pre-strains are shown to effectively avoid the two failure modes. These studies lay a solid foundation to facilitate the use of DE materials, structures, and devices in a wide range of applications such as biomedical devices, adaptive systems, robotics, energy harvesting, etc.

A biotemplate of grapefruit exocarp was used to synthesis porous hierarchical SnO 2 and its gas sensing properties were investigated in this manuscript. Biomorphic SnO 2 with lamellar and plicated membranes and porous walls were synthesized by using grapefruit exocarp template combining with ultrasonic shaking and following calcination. The porous hierarchical structure of biomorphic SnO 2 was characterized by field emission scanning electron microscope, transmission electron microscopy, nitrogen adsorption–desorption isotherm, etc. The biomorphic SnO 2 exhibits small grain size around 10 nm, a relatively large BET surface area and mesoporosity. Growth mechanism of biomorphic SnO 2 was proposed. The sensing properties of the biomorphic SnO 2 to formaldehyde vapor were measured. The optimal operating temperature of the sensor was 200 °C and the response value of the sensor to 10 ppm formaldehyde was 50. The sensor showed a good selectivity to formaldehyde in methanol, acetone, toluene, benzene and ammonia. The stability and the effect of humidity of the sensor were also tested. The gas sensing mechanism of the biomorphic SnO 2 to formaldehyde was analyzed briefly.

We study the electromechanical and electrical behaviors of a PN junction in a multiferroic composite fiber, consisting of a piezoelectric semiconductor (PS) layer between two piezomagnetic (PM) layers, under a transverse magnetic field. Based on the derived one-dimensional model for multiferroic composite semiconductor structures, we obtain the linear analytical solution for the built-in potential and electric field in the junction when there is no applied voltage between the two ends of the fiber. When a bias voltage is applied over the two ends of the fiber, a nonlinear numerical analysis is performed for the current–voltage relation. Both a homogeneous junction with a uniform PS layer and a heterogeneous junction with two different PSs on different sides of the junctions are studied. It is found that overall the homogeneous junction is essentially unaffected by the magnetic field, and the heterojunction is sensitive to the magnetic field with potential applications in piezotronics.

In order to overcome the poor lubricity of zinc dialkyldithiophosphate (ZDDP) in aluminum contacts, ZnO nanoparticles (ZODDP) modified with dialkyldithiophosphoric acid were prepared through one step process from ZDDP. Compared with ZDDP the sulfur and phosphorus contents of ZODDP decreased by 77.9%～82.8% and 77.3～80.7%. respectively. The tribological properties of ZODDP as the additives of diisooctyl sebacate (DIOS) in steel-aluminum contacts were evaluated on ball-on-disk tribometer. Compared with ZDDP the friction coefficient (cof) and wear rate (wr) of ZODDP decreased by 10.37% and 71.74% respectively. The ZnO nano cores in ZODDP enriched on frictional surface, which avoided the direct contact between friction pairs. The weak chemical interaction between ZnO nano-core and modifier promoted the tribological reaction between modifier and aluminum disks. ZODDP is expected to be a cheap and easily available lubricant additive for aluminium-based materials lubricating.