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This paper investigates the electromechanical performance of textile fabric with conductive yarn elements for data transmission capabilities. Electromechanical experiments were conducted to evaluate the electrical response of copper yarn elements stitched axially to the textile fabric, while assessing the mechanical response of the system during tensile tests under axial loading. The results indicated that the yarn element exhibited low electricomechanical coupling below 1.5% strain, making it suitable for consistent electrical performance during low mechanical strain conditions. Computational models were also developed and correlated with the experimental results of the conductive yarn. The computational model was then expanded to investigate the effect of the braiding angle in the braiding system, providing insights into how these parameters influence the system's performance. Overall, this research contributes valuable insights into the electromechanical behavior of textile fabric with conductive yarn elements, and presents a framework for optimizing data transfer capabilities in e-textiles and smart textile applications. The findings open opportunities for further advancements in the design and engineering of functional textiles for a wide range of applications. [ABSTRACT FROM AUTHOR]

Ionomeric polymer‐metal composites (IPMC) are advanced materials designed to mimic biological systems. Their performance depends on various factors, including electrical stimulus intensity, membrane hydration, ionic migration, and Young's modulus. However, there is a lack of studies in the literature investigating how the water absorption capacity and elastic modulus change over time in IPMCs. Understanding the hydration level variation as a function of time is essential because as this parameter deviates, the ionic migration capacity and Young's modulus also change, altering the device's electromechanical efficiency over time. To address this research gap, Nafion/Pt‐based IPMC devices exchanged with four monovalent cations (H+, Li+, Na+, and K+) and one ionic liquid (1‐butyl‐3‐methylimidazolium—BMIM+) were prepared, and a comprehensive investigation on how the water absorption capacity and Young's modulus vary as a function of time, relative humidity (RH), and counterion size was performed. The results revealed that the water uptake capacity is significantly higher and occurs more rapidly at higher RH levels and when the counterion's ionic radius decreases. Consequently, the time required for the device to reach osmotic equilibrium can range from 40 to 270 min, depending on the RH and counterion used. Furthermore, it was observed that the first natural frequency and Young's modulus also exhibit time‐dependent behavior. Under constant RH conditions, the mechanical properties of the IPMC can vary by up to 50% in less than 60 min. Notably, the combined results from water uptake capacity, Young's modulus, electrochemical impedance spectroscopy, and electromechanical response analyses (including blocking force, displacement, displacement rate, current, coulombic efficiency, and voltage) suggest that a morphological transformation within the polymer is likely to occur once RH exceeds 60%. This finding strengthens the hypothesis that ion migration is mainly influenced by their movement through Nafion's ionomeric channels rather than the filling of ionic agglomerates. [ABSTRACT FROM AUTHOR]

The enhanced and reliable high-power performance of x Pb(Mn 1/3 Nb 2/3)O 3 –(1- x)Pb(Zr 0.5 Ti 0.5)O 3 –0.5mol%Co 2 O 3 piezoelectric ceramics (x PMN–(1- x)PZT–Co; x = 0.04–0.10) has been achieved. It is noteworthy that the vibration velocity (υ 0) of the 0.08PMN–0.92PZT–Co ceramic reaches up to 0.9 m/s, which is 2.25 times that of commercial PZT4 ceramics (∼0.4 m/s). The high υ 0 of the 0.08PMN–0.92PZT–Co ceramic is attributed to its excellent electromechanical parameters: d 33 = 405 pC/N, Q m = 1405, and k p = 0.61. The 0.08PMN–0.92PZT–Co ceramic achieves a relatively low high-field tan δ (tan δ = 3.74% at 500 V/mm), thereby suppressing heat generation. Additionally, the significantly high Curie temperature (T c) value of 346 °C for the 0.08PMN–0.92PZT–Co ceramic stabilizes the ferroelectric phase. Therefore, the 0.08PMN–0.92PZT–Co ceramic exhibits long-term reliable high-power performance by maintaining a stable υ 0 of 0.9 m/s and slight temperature rise within 100 min. [ABSTRACT FROM AUTHOR]

The development of high-temperature lead-free piezoelectric ceramics with excellent electromechanical properties under low field remains a key challenge. A series of 0.995(xBiFeO 3 -(1-x)BaTiO 3)-0.005Bi(Zn 0.5 Hf 0.5)O 3 ceramics were designed via modulating phase composition. The excellent electromechanical properties of d 33 * = 511 pm/V (45 kV/cm) at room temperature and S = 0.476 % (d 33 * = 1190 pm/V, 40 kV/cm) at 120 ℃ were achieved in the x = 0.67 ceramic owing to the synergistic contribution of phase composition and domain evolution. The XRD results verify that the x = 0.67 ceramic is dominated by the pseudocubic phase. The PFM results in the x = 0.67 and 0.71 ceramics confirm that the domain structures consist of nanodomains with strong and weak piezoelectric responses. More importantly, the temperature and voltage-dependent domain evolution testify the nanodomains are easier to switch in the x = 0.67 ceramic. This work provides a strategy to optimize the electromechanical performance at the low field and a deeper understanding of BF-BT-based piezoceramics. • The 0.995(xBF-(1-x)BT)-0.005BZH high temperature ceramics with multiple phases coexisting are successfully fabricated. • The ceramic with x = 0.67 obtained excellent electrostrain property of d 33 *= 511 pm/V under low electric field. • The voltage and temperature-dependent in-situ domain structure and dynamics evolutions are characterized systematically. [ABSTRACT FROM AUTHOR]

Due to the good conductivity and adjustable mechanical properties, ionic conductive hydrogel is considered an ideal candidate for use in wearable electronic devices. However, maintaining good flexibility, conductivity, and high sensitivity of electromechanical performance, though highly desirable, remains a great challenge. In this work, a zwitterionic ionic conductive hydrogel (CMHZ: chitosan/polyacrylic acid-acrylamide/ZnSO4) was prepared with excellent mechanical properties, ionic conductivity, and high sensitivity. The CMHZ showed excellent adjusted mechanical properties (up to 1210% tensile strain under 0.15 MPa, toughness 5.42 MJ/m3) and good shape-recovery ability. Meanwhile, the free-moving metal ions in the hydrogel guaranteed the CMHZ with good conductivity (33.73 mS/cm). More importantly, the unique zwitterionic structure made the hydrogel have a wide working voltage range (0 - 2.0 V), which endowed the hydrogel with a significant improvement of sensitivity up to GF = 4.22. Based on these obvious advantages, the CMHZ hydrogel was used as a stretchable sensor demonstrated high-sensitivity physiological signal detection and motion direction recognition, suggesting wide potential in flexible electronic devices.

Ionomeric Polymer-Metal Composites (IPMCs) with a layered metal/polymer/metal structure are innovative biomimetic materials widely used in applications such as actuators, sensors, artificial muscles, and robotics due to their dynamic response to electrical stimuli. Nafion® is commonly used for these applications but is associated with high costs, low water retention, and poor performance at elevated temperatures. To address this, sulfonated poly(ether ether ketone) (SPEEK) is a promising and cost-effective alternative. This study focuses on evaluating the viability of SPEEK in IPMCs under varying environmental conditions, specifically a wide range of relative humidity (RH) levels (30%, 60%, and 90%) and two different counterions (H+ and Li+). FTIR tests confirmed the successful sulfonation of SPEEK, and sulfonation degrees (SD) of 44%, 72%, and 91% were determined by titration. Results indicate that increased SD leads to higher hydration levels, enhancing performance as actuators. Regarding electromechanical performance, SPEEK-based IPMCs demonstrated results comparable or superior to Nafion. Higher RH positively influenced electromechanical performance, increasing displacement and displacement rate values. Additionally, electrochemical/mechanical tests confirmed that, for the H+ counterion, SPEEK exhibited superior performance. In conclusion, SPEEK-based IPMCs, especially with H+ as the counterion, can potentially replace Nafion, offering a cost-effective alternative with favorable electromechanical performance under varying environmental conditions. [Display omitted] • Highly sulfonated PEEK emerges as a cost-effective alternative to Nafion IPMCs, with favorable electromechanical performance. • SPEEK IPMCs with H+ counterion exhibit superior electromechanical's performance under varied environmental conditions. • Higher SD increased hydration levels. SPEEK IPMCs actuation performance were equivalent to Nafion under RH 60/90%. • Innovatively developed IPMCs based on sulfonated PEEK show no reverse relaxation, even under high displacement rates. [ABSTRACT FROM AUTHOR]

To avoid the damage of the microprobe to the wafer, the magnetorheological (MR) damping loading was used. The problem of low repeated positioning was solved by limiting the relative rotation between the probe and cylinder. The experimental results show that the damping performance was similar between the cuboid and cylinder damper. The repetition accuracy of cuboid was more than circular cylinder damper two times. Then, the electrical properties of probe with the cuboid damper were tested under different damping currents, loading velocities, and loading displacements, and the contact resistances fluctuated in the range of 0.85–1.4 $\Omega $. Finally, the mathematical models of pressure and contact resistance were established using the loading speed of 20 mm/s and loading displacement of 300 $\mu \text{m}$. The relationship between the pressure and contacting resistance of probe was revealed with the new damper during loading process and unloading process. [ABSTRACT FROM AUTHOR]

In recent years, piezoelectric micromechanical ultrasonic transducers (PMUTs) have received widespread attention. The deployment of PMUTs in humid environment exposes them to changes in relative humidity, which effects their electromechanical performance. This paper investigates the effect of humid environments (30 %−80 %) on the electromechanical performance of uncoated PMUTs from the perspective of electromechanical conversion model and equivalent circuit. Two types of transducers with different top layer materials were experimented to compare the effects of moisture absorption on the electromechanical performances of the transducers. The top layer material of Device A is SiO 2 film, and the top layer material of Device B is Si 3 N 4 film. The experimental results show that with the rise of relative humidity, the frequency of Device A decreases by −0.47 %, while the frequency of Device B increases by 0.13 %, and the phase resonance peaks of both increases by 0.441° and 0.285°, respectively. Equivalent circuit fitting was conducted on the impedance characteristics of Device A and Device B, and the fitting results were discussed based on acoustic impedance and moisture absorption theory. The electromechanical performances of the two devices show a different variation trend, with the potential reason being that Device A is mainly affected by the combined effects of moisture absorption leading to a decrease in Young's modulus of the membrane and a decrease in the acoustic impedance of the humid air, while Device B is mainly affected by the acoustic impedance. [Display omitted] • The effect of humid environment on the electromechanical performance of uncoated PMUT. • The potential reason of effect is analyzed by conversion model and equivalent circuit. • Different top layer materials of PMUT (SiO 2 , Si 3 N 4) exhibit different variation trends. • PMUT with SiO 2 is mainly affected by moisture absorption and acoustic impedance. • PMUT with Si 3 N 4 is mainly affected by acoustic impedance. [ABSTRACT FROM AUTHOR]

Despite the overwhelming advantages of high theoretical specific energy and low-cost, the realistic application of lithium-sulfur batteries is still restricted by the shuttle effect of intermediate polysulfides, low conductivity of sulfur and volume variation during charging and discharging. Tailored sulfur cathode is of significant importance for realizing high-performances. This study reports a carbon nanotube (CNT)-modified polar Co(PO 3) 2 /CoP nanoparticles embedded nitrogen-doped porous-shell carbon polyhedron (CNT/CPO/CPNC-1) as a sulfur host to simultaneously overcome the barriers of lithium–sulfur batteries. The shuttle effect can be significantly restrained by the physical confinement of unique porous structure and the chemical adsorption/catalysis conversion of polar Co(PO 3) 2 /CoP and the heteroatom doping of nitrogen. Meanwhile, the porous-shell carbon with interconnected carbon nanotubes can simultaneously provide a conductive framework, facilitate rapid electrical transport, and enable a large inner space to buffer volume expansion. As a result, CNT/CPO/CPNC-1/S cathode demonstrates an excellent reversible capacity of 1371.3 mAh g−1 at 0.1 C with stable Coulombic efficiency of 98% and an outstanding cycling stability with an ultralow capacity decay rate of 0.048% per cycle (500 cycles at 1.0 C). This work pioneers the employment of Co(PO 3) 2 /CoP/carbon hybrid materials as sulfur host and sheds a new light to explore the high-performance lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

The YBa2Cu3O7-x (YBCO) coated conductor (CC) is one of the most promising superconducting materials because of their high critical current (Ic) and low dependency of the Ic on the external magnetic field. For superconducting applications, a large number of joints are required to join relatively short YBCO CC tapes. In this paper, we study the electromechanical behavior of lap-jointed YBCO CC tapes fabricated by etching Cu stabilizer at its service temperatures (77 K) under self-field. The effects of etching Cu stabilizer on Ic and joint resistance (Rj) of YBCO CC tapes were discussed. The Rj was reduced and the Ic values of the joints are consistent with the parent CCs tape by etching the Cu stabilizer. Preferable electrical properties under applying axial tension are achieved and proved by the axial tension tests and finite element simulations. This fabrication technique is a unique practicable solution to reduce joint resistance for YBCO CC tapes with thicker metal stabilizing layers and improving electromechanical performance in second generation high temperature superconductor (2G HTS) devices. [ABSTRACT FROM AUTHOR]

Previous studies have revealed that fiber-reinforced tubular dielectric elastomer actuators (TDEAs) exhibit unique characteristics, such as coupled deformation. Therefore, the present study focuses on the electromechanical behavior of fiber-reinforced TDEAs and analyzes induced coupled bending–twisting deformation analytically and numerically. An analytical framework is derived from the Helmholtz free energy of the system and, using the variation method, leads to equilibrium equations. Despite the limitation of homogeneous deformation, the results indicate relevant facts about the electromechanical behavior and stability of the considered TDEA. On the other hand, a numerical method is devised based on the nonlinear continuum, electro-elasticity, and large deformation theory. The resultant model and presented tangent modulus are validated using experimental data. The model makes it possible to develop a FEM algorithm and explore the behavior of the TDEA under various loading and boundary conditions. For example, the current paper presents the final deformation of a fiber-reinforced TDEA under internal pressure, axial force, and torque. It also explores the bending deformation of a designed tubular bending actuator using numerical analysis and the developed model. Analytical and numerical results share similar trends in longitudinal, radial, and torsional deformations before instability. It is also evident that for voltages higher than the critical voltage, when instability is detected, fiber orientation may cause more significant effects. Analytical and numerical findings confirm coupled deformations in different directions. • An experimentally-validated model for anisotropic dielectric elastomer actuators. • Numerical and analytical solutions for tubular dielectric elastomer actuator. • Investigations of tubular dielectric elastomer actuator's coupled deformation. • Coupled electromechanical bending–twisting​ behavior of a tubular actuator. [ABSTRACT FROM AUTHOR]

To reveal the electro-viscoelastic performance of a tubular dielectric elastomer actuator, a dissipative model for the actuator is formulated by adopting the nonlinear theory of viscoelastic dielectrics. The actuator is made by rolling a layer of dielectric elastomer membrane into a tube, which is then fixed tightly with two rigid disks at top and bottom edges respectively. Once actuated by internal pressure and voltage, the tube inflates and deforms into an out-of plane shape, undergoing large deformation. To depict the deformation, the non-equilibrium thermodynamics is employed to derive the state equations and the governing equations, and to characterize the dissipative process, a rheological spring-dashpot model is applied to obtaining the kinetic equations. Numerical simulation is conducted by a joint use of the shooting method and the improved Euler method, and the variations of the considered variables and the profiles of the deformed tube are obtained and demonstrated graphically. The effects of the internal pressure, the voltage as well as the aspect ratio of the tube on the performance of the actuator are considered. The results show that for small pressure or small voltage, the actuator can eventually evolve into a stable state, while for large pressure or large voltage, the actuator can't reach a stable state due to the occurrence of purely mechanical instability or electromechanical instability. As for the aspect ratio, it significantly influences the performance of the actuator. It is hoped that the approach may provide a better understanding of the electro-viscoelastic performance of such actuators and some guidelines in designing such actuators. [ABSTRACT FROM AUTHOR]

Abstract Despite promising characteristics of high energy density and low material cost, lithium-sulfur (Li S) batteries show practical limitations in poor cycling life and low Coulombic efficiency due to the fatal "shuttle effect" of soluble polysulfides. Here, a dual polysulfide confinement strategy is designed by fabricating an in-situ N/P co-doped carbon, which is originating from versatile silk cocoons through a combined technology of phosphoric acid activation and carbonization and acts as both sulfur host and self-standing interlayer in Li S batteries. The N/P co-doped porous carbon host (NPPC) provides both the physical restriction and chemical adsorption of polysulfides, while the polar interlayer is used as not only an efficient barrier for blocking polysulfides but also a second current collector, which can reuse the sulfur species, enhance the cycling stability and rate capacity. With this rational design, the NPPC/S cathode with the free-standing interlayer exhibits an initial specific capacity of 1412.6 mAh g−1 at 0.1 C, outstanding cycling stability with the ultra-low capacity decay of 0.032% per cycle over 500 cycles at 1.0 C and splendid rate performance with 758.1 mAh g−1 at 2.0 C. Our work provides an eco-friendly and dual employed strategy for boosting the commercialization of Li S batteries. Graphical abstract Image 1 Highlights • A dual confinement strategy for polysulfides has been proposed. • Porous sulfur host and functional interlayer have been successfully prepared. • Physical and chemical synergistic adsorption is used to encapsulate polysulfides. • The cathode with interlayer exhibits excellent electrochemical properties. [ABSTRACT FROM AUTHOR]

Flexible electronic devices have attracted considerable attention in recent years. Textile fabrics have been widely used to fabricate flexible strain sensors owing to their high flexibility. However, the ordinary textile fabric is electrically insulating, which limits their sensitivity to strain. In this article, cotton fabric endowed with high electrical conductivity was prepared by a two-step process of dipping and coating. It was firstly modified with a continuous reduced graphene oxide thin film by using a dipping method and then coated with silver (Ag) thin films by using a magnetron sputtering system. In addition, a strain sensor was also fabricated using the resultant fabric, namely the silver/graphene cotton (Ag/G-coated cotton). Our results revealed that the Ag/G-coated cotton fabric sputtered at 200 W for 25 min has the highest electrical conductivity and its average surface resistance is 2.71 Ω/sq. Moreover, the fabricated strain sensor based on Ag/G-coated cotton fabric exhibited the advantages of high sensitivity, large workable strain range (0-20%), fast response and great stability. What’s more, real-time monitoring of human motions, such as flexing and finger rotation, could be achieved by the sensor. Overall, the effective flexibility and high electrical conductivity of the Ag/G-coated cotton fabric have been validated effectively and make it one of the promising candidates for its applications in wearable electronic devices. [ABSTRACT FROM AUTHOR]

Flexible electronic devices have attracted considerable attention in recent years. Textile fabrics have been widely used to fabricate flexible strain sensors owing to their high flexibility. However, the elasticity of ordinary textile fabrics is low, which limits their strain sensing range. In this article, we used a simple method to fabricate flexible strain sensing fabrics (FSSFs) through the coating of graphene oxide (GO) nanosheets on elastic nylon/polyurethane (nylon/PU) fabric, followed by reduction of GO with sodium borohydride. The reduced graphene oxide (RGO) nanosheets were adsorbed on the elastic fabrics to impart electrical conductivity to the fabrics. The coated fabrics were characterized with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman scattering spectroscopy. The electromechanical performance and strain sensing properties of the FSSF were investigated. The fabricated strain sensor exhibited high sensitivity, a large workable strain range (0–30%), fast response and great stability. The mechanical property of fabrics did not change remarkably after the treatment with RGO. The surface resistance of the RGO/nylon/PU only increased from ∼112 KΩ/m 2 to ∼154 KΩ/m 2 after 8 washing cycles, exhibiting good washability. Furthermore, real-time monitoring of human motions, such as bending of finger and rotation of wrist, was achieved by the as-prepared FSSF. The RGO/nylon/PU fabrics as flexible strain sensors have potential applications in wearable electronic devices. [ABSTRACT FROM AUTHOR]

Dual responsive material composed of magnetite nanoparticle (MNP) and graphene nanosheet (GP) as a hybrid filler and polyurethane (PU) as an electrostrictive matrix was fabricated. The hybrid filler was synthesized by the in-situ growth of MNP on the GP surface. The obtained hybrid particles behaved simultaneously as a superparamagnetic and conducting material. The hybrid-composites possessed electronic polarization and high response towards electric field, as they showed excellent recoverability and fast response during the temporal test under electric field. The highest storage modulus sensitivity was obtained from the 0.5%v/v MNP-GP/PU at the value of 3.97 under the applied electric field of 2 kV/mm. In the deflection experiment, the 0.5%v/v MNP-GP/PU composite exhibited the largest bending distance of 13.65 mm under the electric field of 500 V/mm. On the other hand, the 3.0%v/v MNP-GP/PU yielded the maximum bending of 15.35 mm under the magnetic field of 1650 G. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride)-based ferroelectric polymers have large and tunable dielectric permittivity (εr), but rather high Young’s modulus (Y), which limits its electromechanical response when used as actuators. In this work, a silicone oligomer involving amino groups is employed to crosslink a non-crystallized poly(vinylidene fluoride-chlorotrifluoroethylene) matrix bearing double bonds (P(VDF-CTFE-DB)) via addition reaction. Thanks to the flexible silicone molecules, the modulus of the hybrids is reduced over 30% when compared with the pristine matrix. Most interestingly, the εr of the hybrids is improved to nearly 100% higher than that of the matrix when the silicone content reaches 30 wt %. This may be due to the dilution effect of silicone molecules, which favors macromolecular chain rearrangement and dipole orientation of the hybrids under an applied electric field. As a result, electric-field activated displacements of the above hybrid increases to 0.73 mm from 0.48 mm of the matrix under 60 MV/m. The maximum electric field-induced thickness strain increases from 1% of the matrix to nearly 3% of the crosslinked hybrid. This work may provide a facile strategy to fabricate PVDF-based hybrids with enhanced electromechanical performance under low activating voltage.

Conductive cotton fabric was prepared by coating single-wall carbon nanotubes (CNTs) on a knitted cotton fabric surface through a “dip-and-dry” method. The combination of CNTs and cotton fabric was analyzed using scanning electron microscopy (SEM) and Raman scattering spectroscopy. The CNTs coating improved the mechanical properties of the fabric and imparted conductivity to the fabric. The electromechanical performance of the CNT-cotton fabric (CCF) was evaluated. Strain sensors made from the CCF exhibited a large workable strain range (0~100%), fast response and great stability. Furthermore, CCF-based strain sensors was used to monitor the real-time human motions, such as standing, walking, running, squatting and bending of finger and elbow. The CCF also exhibited strong electric heating effect. The flexible strain sensors and electric heaters made from CCF have potential applications in wearable electronic devices and cold weather conditions.

• Dielectric elastomer material with enhanced electromechanical performance. • Design strategy based on disulfide metathesis coupled with hydrogen bonding. • Fast room-temperature healability with 96% self-healing efficiency. • The dynamic exchange characteristic leads to a decrease in modulus. • More than two times actuation performance improvement in dielectric actuator. Dielectric elastomers are indispensable for soft actuators due to their fast actuation response and diverse configuration. However, the existing dielectric elastomers have poor electromechanical performance and are vulnerable to damage or failure, highlighting an urgent need for materials with remarkable dielectric, mechanical and self-healing properties. Aiming at these requirements, we herein propose an extraordinary design strategy of supramolecular elastomer by combining multitype dynamic chemical bonds via synthesizing, which is different from most previously reported dielectric elastomers. This strategy includes three typical features: (i) The S-S metathesis coupled with multi-degree hydrogen bonds provides the supramolecular poly(urethane-urea) (PUU) elastomer with fast room-temperature healability and ultrahigh efficiency. After mechanical damage, the electrical property completely recovered after ∼ 20 min restoration, and the mechanical performance is restored by 96% after healing at room temperature for 3 h, much higher than that of the elastomer without disulfide bonds (13%). (ii) Highly polar urethane and urea groups endow the supramolecular PUU elastomer with excellent dielectric properties (ε r = 10.9@1 kHz). (iii) The aliphatic disulfide bonds have the capability to reduce the Young's modulus from 2.98 to 1.76 MPa by virtue of its dynamic exchange characteristic. These merits allow the resulting actuator to be more sensitive to driving field. Compared with the control sample, the area strain (at 60 MV/m) and bending angle (at 30 MV/m) for supramolecular elastomer is ∼ 4 and ∼ 2.2 times higher, respectively. As an example, a switch controlling a series circuit illustrates the potential application of such electric-field-activated actuators in high-voltage devices. [ABSTRACT FROM AUTHOR]

An electrophoretic deposition (EPD) process with high deposition rate was used to fabricate a curved piezoelectric thick film devoted to high-frequency transducers for medical imaging. Niobium-doped lead zirconate titanate (PZTNb) powder was stabilized in ethanol to prepare a suspension with high zeta potential and low conductivity. A gold layer, pad-printed and fired on a curved porous PZT substrate, was used as the working electrode for the deposition of the PZTNb thick film. This substrate was chosen because it has the required properties (acoustic impedance and attenuation) to be used directly as a backing for the high-frequency transducer, leading to a simplified process for transducer assembly with this integrated structure. PZT-Nb thick films were also deposited by EPD on flat gold-coated alumina substrates as a reference. The thickness of the films was between 20 and 35 μm, and their electromechanical performance was comparable to standard PZT bulk ceramics with a thickness coupling factor of 48%. For the curved thick film, the thickness coupling factor was slightly lower. The corresponding integrated structure was used to fabricate a transducer with a center frequency of 40 MHz and an f-number of 2.8. It was integrated into a realtime ultrasound scanner and used to image human forearm skin; the resulting images showed, for the first time, the efficacy of the EPD process for these imaging applications. [ABSTRACT FROM AUTHOR]

This paper presents the fabrication, characterization, and modeling of electrodynamic microactuators. The actuators are piston-type devices, each comprising of a circular flexible polydimethylsiloxane membrane, a multi-turn Cu coil, and an integrated powder-based NdFeB permanent magnet. The devices are fully batch-fabricated in a single wafer using only three masks. Ranging in diameter from 2.5 to 5.2 mm, three different device designs are quasi-statically and dynamically characterized for their electromechanical performance. The resonant frequencies of the three actuators range from 224 to 820 Hz. The maximum displacements span from 4 to 64 μm for an input power ranging from 250 to 525 mW. The experimental results are supported by a parametric lumped element model of the transducer. [ABSTRACT FROM AUTHOR]

Thick film two phase, 0-3 composite PZT-epoxy dome- shaped structures have been fabricated for the first time using a modified solvent and spin coating technique, where a PZT and ethanol solution was dispersed in an epoxy matrix, combined with a hardener, spin coated onto stainless steel sheets, and poled at ~2.2 kV/mm. The electro-mechanical performances of the films were investigated as a function of volume fraction of PZT. The volume fraction of PZT was varied from 0.1 to 0.7 and the piezoelectric coefficients d and d, and the capacitance, C, were measured, and used to calculate the effective dielectric constants. The values for d, d, C and dielectric constant were 1.06 pC/N, 0.74 pC/N, 6.0 pF and 76.1 respectively, at 70 % volume fraction of PZT. The surface topography and morphology were examined via AFM and SEM. The piezoelectric strain coefficients, capacitance and effective dielectric constant increased with increasing PZT content, in addition to the surface roughness. Agglomeration of PZT particles and surface crevices were observed on sample surfaces, which are most likely due to surface tension and air bubbles formed during the mixing process. [ABSTRACT FROM AUTHOR]

New target applications for microfluidic devices have been focused on home usability, wearability and cost-effectiveness. Towards these goals, in this work, a controllable, bendable, and all‑organic, nozzle‑diffuser microfluidic pump was designed, fabricated and tested. First, to resolve the crucial issue of high driving voltage, the ferroelectric polymer poly(vinylidene fluoride‑trifluoroethylene) (P(VDF‑TrFE)) was optimized by adding core‑shell structured Al 2 O 3 @CNT nanofillers. The membrane so developed with 1.1 wt% Al 2 O 3 @CNT showed an increase by nearly 7 times in the induced strain in comparison to the neat P(VDF‑TrFE) at low electric fields, because the modified membrane simultaneously achieved a lower coercive electric field and a higher polarization. Accordingly, the required operating voltage of the microfluidic pump integrated with optimized membrane significantly decreased from 1000 V to 160 V. Meanwhile, this pump exhibited a wider range of flow rates (13–135 µL/min) than the reported results, associated with the higher output pressure in our membranes. Importantly, the designed pump still possessed an excellent controllability of the fluidic processes, though it underwent a large bending up to 74°. Consequently, the extremely promising application of the as‑prepared microfluidic pump in wearable, biomedical devices was demonstrated. • The optimized piezoelectric membrane exhibits the improved induced strain, breakdown strength and elastic modulus, simultaneously. • The driving voltage of the microfluidic pump with the 1.1 wt.% nanocomposite membrane was substantially reduced from 1000 V to 160 V. • The designed bendable microfluidic pump demonstrates an excellent controllability for liquid underwent bending to a maximal angle of 74°. • The as-prepared bendable microfluidic pump exhibits a huge potential application in wearable devices under a driving voltage of 50 V. [ABSTRACT FROM AUTHOR]

[Display omitted] • A sensor consisting of carbon nanotubes is fabricated. • GF is found experimentally in the range of 8–8.25. • This sensor is embedded gradually at 0°,+45°,90°,−45° directions in composites. • These composite samples are then tested under tensile and flexural cyclic loading. • The CM sensor showed good strain monitoring behavior in real-time. • The sensor also showed distinct detection signals because of their respective positions. In this study, a flexible conductive membrane (CM) consisting of a network of carbon nanotubes is produced and the electromechanical behavior of this CM was studied experimentally and the gauge factor (GF) of CM was in the 8–8.25 range. Then, a multi-mode strain detection is carried out in composites using this CM sensor. The CM is embedded gradually at directions i.e. 0°, +45°, 90°, −45° between the plies for real-time/in-situ strain monitoring. The composite specimens are then cut in star profile and then tested under tensile and bending cyclic loading. There is a good reproducibility in the results and the mechanical response of composite correlated perfectly with the electrical resistance of the CM sensor however, a sensor in each position showed distinct behavior. The results established that the CM sensor exhibited good potential as a flexible strain sensor for in-situ monitoring of composites and can provide detection over a large section and unapproachable locations. [ABSTRACT FROM AUTHOR]

• The dependency relationship between the parameters of DE and the relative humidity are obtained by fitting presupposed models to the experimental data. • The humidity effect on static and dynamic electromechanical performances is explored. • Phase paths and Poincaré maps are utilized to detect the humidity effect on the stability and periodicity of the nonlinear vibration. • The variation tendency of resonant frequency is investigated by continuously varying the relative humidity. As is known, the ambient environment, such as temperature and humidity, may affect the electromechanical properties of dielectric elastomer (DE). In this research, we carry out an analysis to explore the humidity effect on electromechanical performance of a viscoelastic DE, by prescribing the shear moduli, the viscous damping, and the relative dielectric constant of the DE are humidity-dependent values. The dependency relationships between these parameters and the relative humidity are obtained by fitting the presupposed models to experimental data. The humidity effect on static and dynamic electromechanical performances is explored by exhibiting the creeping deformation of both elastic and non-elastic stretch of the viscoelastic DE. Phase paths and Poincaré maps are utilized to detect the humidity effect on the stability and periodicity of the nonlinear vibration. Finally, the variation tendency of resonant frequency of the viscoelastic DE system is investigated by continuously varying the relative humidity. As is known, the ambient environment, such as temperature and humidity, may affect the electromechanical properties of dielectric elastomer (DE). In this research, we carry out an analysis to explore the humidity effect on electromechanical performance of a viscoelastic DE by prescribing the shear moduli, the viscous damping, and the relative dielectric constant of the DE are humidity-dependent values. The dependency relationship between these parameters and the relative humidity are obtained by fitting presupposed models to the experimental data. The humidity effect on static and dynamic electromechanical performances is explored by exhibiting the creeping deformation of both elastic and non-elastic stretch of the viscoelastic DE. Phase paths and Poincaré maps are utilized to detect the humidity effect on the stability and periodicity of the nonlinear vibration. Finally, the variation tendency of resonant frequency of the viscoelastic DE system is investigated by continuously varying the relative humidity. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Well-designed pentablock copolymer with softness (110 kPa) yet strength (20.2 MPa). • New dielectric elastomer with actuation strain up to 184% with 1.5 × 1.5 prestrain and 72% without prestrain. • Ultrathin films less than 20 μm fabricated by simple blade casting and stretching. • Very large area strain actuated by far below 1 kV (30% at 240 V, 93% at 680 V) for ultrathin films. Electrically active dielectric elastomer has been a leading technology for artificial muscle. It remains a great challenge to significantly reduce the actuation voltage down to far lower than 1 kV. Here, we report that well-designed pentablock copolymer could be an excellent strategy to address the challenge. Particularly, pentablock copolymer (S EHA S) 2 (S for polystyrene, EHA for poly(2-ethylhexyl acrylate)) with suitable composition exhibits ultrasoft-yet-strong property, which is rarely observed in an elastomer. The sparse entanglements together with relatively high chain-loop concentration in the EHA phase make the material significantly softer than most elastomers. The middle block of polystyrene reinforces the hard nanodomains to provide the high tensile strength. The ultrasoft-yet-strong property together with high extensibility and good processability allows us to conveniently fabricate an ultrathin actuator, which is highly responsive to low voltage (area strain 93% at 680 V and 30% at 240 V). [ABSTRACT FROM AUTHOR]

• CF sensor was developed using unidirectional carbon filaments aligned together. • The electromechanical performance of CF recorded gauge factor in the range of 10.2–10.8. • The electrothermal behavior of CF detected the change in surrounding temperature. • Empirical relations correlated electrical response with both stimuli, respectively. • CF exhibited good potential as a flexible sensor for in-situ monitoring applications. Structural health monitoring (SHM) is a vastly growing field consisting of sensors embedded in or attached with the structure which respond to the strain or other stimuli to monitor the deformation in real-time. In this study, a carbon fiber (CF) sensor was developed using unidirectional Polyacrylonitrile (PAN) carbon filaments aligned straightly together and its sensitivity was calculated experimentally, with the gauge factor (GF) in 10.2–10.8 range. The electro-thermal behavior of this CF sensor showed distinct performance and detected the change in the surrounding temperature. There is a good reproducibility in the results in both piezoresistive and electro-thermal behavior of the CF sensor and its electrical performance showed real-time detection of both mechanical and thermal stimuli. The results established that the CF exhibited good potential as a flexible strain sensor for in-situ monitoring of damage or energy release during the failure of composites. [ABSTRACT FROM AUTHOR]

In this work, aiming to fabricate a pressure sensor using a porous PDMS as a dielectric layer with a large pressure range and a high sensitivity for pressure detection, an improved method was applied through optimizing vacuum-assisted infiltration parameters, in which different size of sugar particles was used as porogen considering the low cost. With this method, a high-performance porous PDMS film with uniform pore size distribution and no particle residue was successfully obtained without changing its chemical structure. Then, the capacitive pressure sensor was fabricated based on the porous super elastic PDMS dielectric layer. Conductive cloth tape (thickness: 0.1 mm, Shenzhen Huijia Co., Ltd., Shenzhen, China) was used as electrodes. The sensor displayed multiple great properties including a large range of sensing pressures (> 200 kPa), a relatively good sensitivity of 0.023 kPa−1, excellent compression property, good hysteresis and a response time about 155 ms. The sensor remained stables for at least 1000 cycles under 10 and 80 kPa. Due to its high performance, finger and plantar sensors were fabricated and demonstrated as an application of the proposed sensor. • The porous PDMS is obtained by utilizing sugar particles as porogen and vacuum assisted to promote the fabrication process. • The porous PDMS with different pore sizes exhibits high elasticity, no sugar residue and good interconnectivity. • The capacitive pressure sensor based on porous PDMS displays various excellent properties. • The capacitive pressure sensor shows great potentiality in e-skin sensing system and rehabilitation monitoring. Flexible, sensitive and largescale normal pressure sensors are in high demand of rapid development of healthcare and e-skin systems. In this paper, a new capacitive normal pressure sensor was fabricated based on a dielectric layer of superelastic polydimethylsiloxane (PDMS) with uniformly distributed micro-pores. The micro-pores were formed through vacuum-assisted infiltration of PDMS solution using sugar particles as porogen. Results showed that the PDMS layer with uniform micro-pores without sugar residue was successfully obtained. The developed sensor experimentally displayed a high elasticity, a large sensing pressure range (> 200 kPa), a high sensitivity (0.023 kPa−1), a good hysteresis, a fast response (about 155 ms) and a good structural stability and durability for using more than 1000 cycles. Demonstrations of the fabricated sensor in detecting finger grabbing and plantar pressure were performed, indicating it a high potential in the future use of e-skin or rehabilitation monitoring system. [ABSTRACT FROM AUTHOR]

• End block curing increases the electroactuation of a triblock copolymer elastomer. • Electroactuation strain up to 72% and energy density up to 270 kJ/m3 without prestretch. • The elastomer owns −35 °C T g , modulus lower than 1 MPa, and 3 MPa tensile strength. Dielectric elastomers (DEs) featured with fast reversible and large deformation excited by an external electric field show promising applications as leading artificial muscle materials in many emerging technologies. It remains a great challenge to synthesize a DE simultaneously with high electromechanical performance (large actuation strain, high energy density, free of pre-stretch and bracing) and excellent mechanical properties (low Tg, low viscous loss, low modulus, and high mechanical strength). Herein, we propose and demonstrate that end-block-curing ABA triblock copolymer elastomer with well-designed structures is a new strategy to address the challenge by taking advantage of the microphase separation nature of the block copolymer. Particularly, poly(styrene-b-butyl acrylate-b-styrene) (SBAS) with post-curable end blocks, i.e. polystyrene (PS) blocks, are designed and synthesized. Different levels of cyclohex-3-enylmethyl acrylate (CEA) that contains two asymmetric vinyl groups with very different reactivity are incorporated into the end blocks for end-block curing while the molecular weight for each block is fixed. It is found that curing the end blocks enhances the strain-hardening effect during stretch and thus significantly increases the electro-mechanical performance. Without pre-stretch, the DE actuator of the end block cured SBAS exhibits a maximum actuation strain up to 72%, dielectric breakdown strength up to 154 kV mm−1, and energy density up to 270 kJ/m3, which are three, four, and almost fourty times that of the SBAS free of CEA, respectively. The maximum energy density is over 30 times that of mammalina skeletal muscle while the maximum actuation strain is 3.4 times. Interestingly, the improvement in eletromechanical performance is fulfilled with little increase in glass transition temperature (T g), mild increase in modulus, and excellent tensile strength due to the microphase structures. The end-block-cured SBAS retains a low T g of the rubbery phase around −35 °C, relatively low viscous loss of 0.2 at room temperature, a modulus lower than 1 MPa, and tensile strength around 3 MPa, which are attractive in terms of DE device applications. [ABSTRACT FROM AUTHOR]

The quasistatic piezoelectric coefficient (d 33) of the state-of-the-art bulk polymers is lower than 38 pC N−1, extremely restricting their application in the fields of next generation of smart and wearable devices. Herein, a novel soluble and meltable piezoelectric bulk copolyimide with the d 33 of about 420 pC N−1 has been successfully synthesized by co-polymerizing pyromellitic dianhydride with p-phenylenediamine and the specially designed NH 2 -ended imidazole ionic liquid. Molecular structure, solubility, melt processability, and piezoelectricity of the resulting piezoelectric copolyimide have been extensively investigated. Relevant results reveal that the d 33 value of the obtained piezoelectric copolyimide is found to be 10 and 50–100 times higher than the reported bulk poly (vinylidene fluoride) and polyimides, respectively. It still surpasses 250 pC N−1 as the storage temperature approaches 150 °C, evidently higher than that of the previously reported polymer based piezoelectric materials. The developed copolyimide shows outstanding piezoelectricity reliability, benefiting from the semicrystallinity of the resulting copolyimide at room temperature. A maximum output voltage of about 219 mV can be instantaneously obtained once a tiny periodical force is loaded on the copolyimide based piezoelectric nanogenerator (PENG). Meanwhile, an output power of about 1.17 mW can be reached for the developed PENG, implying large potential application in the sectors of smart tactile devices, electronic skins, and self-powered biomedical nanorobots etc. Image 1 • Novel nanogenerator based on soluble and meltable polyimide has been prepared. • Piezoelectricity of the polyimide is equal to that of common piezoelectric ceramics. • d 33 of the copolyimide is 50–100 times higher than those of reported bulk polyimides. [ABSTRACT FROM AUTHOR]

Flexible wearable devices for various applications have attracted research attention in recent years. To date, it is still a big challenge to fabricate strain sensors with a large workable strain range while maintaining their high sensitivity. Herein, we report the fabrication of highly sensitive wearable strain sensors from braided composite yarns (BYs) by in situ polymerization of polypyrrole (PPy) on the surface of yarns after polydopamine templating (BYs-PDA). The electromechanical performance and strain sensing properties of the fabricated braided composite yarn@polydopamine@polypyrrole (BYs-PDA-PPy) were investigated. Because of the unique braided structure of BYs, the BYs-PDA-PPy strain sensors exhibit fascinating performance, including a large workable strain range (up to 105% strain), high sensitivity (gauge factor of 51.2 in strain of 0%-40% and of 27.6 in strain of 40%-105%), long-term stability and great electrical heating performance. Furthermore, the BYs-PDA-PPy sensors can be used in real-time monitoring subtle and large human motions. The BYs-PDA-PPy strain sensors can also be woven into fabrics for large area electric heating. These results demonstrate the potential of BYs-PDA-PPy in wearable electronics.

Poly(vinylidene fluoride)-based ferroelectric polymers have large and tunable dielectric permittivity (εr), but rather high Young’s modulus (Y), which limits its electromechanical response when used as actuators. In this work, a silicone oligomer involving amino groups is employed to crosslink a non-crystallized poly(vinylidene fluoride-chlorotrifluoroethylene) matrix bearing double bonds (P(VDF-CTFE-DB)) via addition reaction. Thanks to the flexible silicone molecules, the modulus of the hybrids is reduced over 30% when compared with the pristine matrix. Most interestingly, the εr of the hybrids is improved to nearly 100% higher than that of the matrix when the silicone content reaches 30 wt %. This may be due to the dilution effect of silicone molecules, which favors macromolecular chain rearrangement and dipole orientation of the hybrids under an applied electric field. As a result, electric-field activated displacements of the above hybrid increases to 0.73 mm from 0.48 mm of the matrix under 60 MV/m. The maximum electric field-induced thickness strain increases from 1% of the matrix to nearly 3% of the crosslinked hybrid. This work may provide a facile strategy to fabricate PVDF-based hybrids with enhanced electromechanical performance under low activating voltage. [ABSTRACT FROM AUTHOR]

Conductive cotton fabric was prepared by coating single-wall carbon nanotubes (CNTs) on a knitted cotton fabric surface through a "dip-and-dry" method. The combination of CNTs and cotton fabric was analyzed using scanning electron microscopy (SEM) and Raman scattering spectroscopy. The CNTs coating improved the mechanical properties of the fabric and imparted conductivity to the fabric. The electromechanical performance of the CNT-cotton fabric (CCF) was evaluated. Strain sensors made from the CCF exhibited a large workable strain range (0~100%), fast response and great stability. Furthermore, CCF-based strain sensors was used to monitor the real-time human motions, such as standing, walking, running, squatting and bending of finger and elbow. The CCF also exhibited strong electric heating effect. The flexible strain sensors and electric heaters made from CCF have potential applications in wearable electronic devices and cold weather conditions.

The bulk materials of three-dimensional graphene (3DG) with high network structure and excellent electrical conductivity have many potential applications in flexible electronics, but the network structure is not very stable due to weak bonding between graphene nanosheets. Here, a polyimide (PI) layer was introduced on the as-prepared 3DG sponge by vacuum infiltration-curing method. The resulting 3DG/PI composite sponges with robust 3D network structure exhibited an excellent electrical conductivity (3.7 S/cm), compression strength (175 kPa), elasticity, and flexibility, as well as outstanding compression sensitivity to resistance and stable piezoresistance effect; namely, they possess a large change in resistance in response to application of small strain and low density, and the resistance change remains favorably stable after performing 300 compress-release cycles, which means that the prepared composite sponges can find wide applications in pressure-sensing or stimulus-responsive graphene system.

A hard template method to prepare N-doped graphene foams (NGF) with superfast template removal was developed through a pyrolyzing commercial polyurethane (PU) sponge coated with graphene oxide (GO) sheets in an ethanol flame. The removal of the template was fast and facile, and could be completed in less than 60 s in an open environment. The synthesized graphene foams consisted of a unique structure of 3D interconnected hollow struts with highly wrinkled surfaces, and the morphology of the hollow struts could be tuned by controlling the GO dispersion concentration. The foams showed high hydrophobicity and were used as absorbents for a variety of organic solvents and oils. The unique NGF structure afforded a high absorption rate and capacity, and a remarkable 98.7% pore volume of the foam could be utilized for absorption of hexane, exhibiting one of the highest capacity values among existing absorptive counterparts. The N-doping brought higher capacitive performance than conventional graphene foams prepared by chemical vapor deposition on nickel foam templates. The NGFs also displayed high elasticity and could recover completely after 50% compressive strain. Owing to easy availability and reduction environment of the flame, complete thermal decomposition of the PU sponge and highly porous open-cell structure, and flame resistance of the graphene foam, the present flame method was demonstrated to be a simple, effective, and ultrafast approach to fabricate ultra-low-density NGFs with good electromechanical response, excellent organic liquid absorption, and high-energy dissipation capabilities.