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IntroductionDietary advanced lipoxidation end products (ALEs), which are abundant in heat-processed foods, could induce lipid metabolism disorders. However, limited studies have examined the relationship between maternal ALEs diet and offspring health.MethodsTo investigate the transgenerational effects of ALEs, a cross-generation mouse model was developed. The C57BL/6J mice were fed with dietary ALEs during preconception, pregnancy and lactation. Then, the changes of glycolipid metabolism and gut microbiota of the offspring mice were analyzed.ResultsMaternal ALEs diet not only affected the metabolic homeostasis of dams, but also induced hepatic glycolipid accumulation, abnormal liver function, and disturbance of metabolism parameters in offspring. Furthermore, maternal ALEs diet significantly upregulated the expression of TLR4, TRIF and TNF-α proteins through the AMPK/mTOR/PPARα signaling pathway, leading to dysfunctional glycolipid metabolism in offspring. In addition, 16S rRNA analysis showed that maternal ALEs diet was capable of altered microbiota composition of offspring, and increased the Firmicutes/Bacteroidetes ratio.DiscussionThis study has for the first time demonstrated the transgenerational effects of maternal ALEs diet on the glycolipid metabolism and gut microbiota in offspring mice, and may help to better understand the adverse effects of dietary ALEs.

Abstract Background Foamy viruses (FVs) are unique nonpathogenic retroviruses, which remain latent in the host for a long time. Therefore, they may be safe, effective gene transfer vectors. In this study, were assessed FV–host cell interactions and the molecular mechanisms underlying FV latent infection. Methods We used the prototype FV (PFV) to infect HT1080 cells and a PFV indicator cell line (PFVL) to measure virus titers. After 48 h of infection, the culture supernatant (i.e., cell-free PFV particles) and transfected cells (i.e., cell-associated PFV particles) were harvested and incubated with PFVL. After another 48 h, the luciferase activity was used to measure virus titers. Results Through transcriptomics sequencing, we found that PREB mRNA expression was significantly upregulated. Moreover, PREB overexpression reduced PFV replication, whereas endogenous PREB knockdown increased PFV replication. PREB interacted with the Tas DNA-binding and transcriptional activation domains and interfered with its binding to the PFV long terminal repeat and internal promoter, preventing the recruitment of transcription factors and thereby inhibiting the transactivation function of Tas. PREB C-terminal 329–418 aa played a major role in inhibiting PFV replication; PREB also inhibited bovine FV replication. Therefore, PREB has a broad-spectrum inhibitory effect on FV replication. Conclusions Our results demonstrated that PREB inhibits PFV replication by impeding its transcription.

Abstract Increasing evidences demonstrate that chlorogenic acid (CGA), a polyphenol with multiple effects such as anti-inflammatory and anti-oxidation, protects against myocardial ischemia–reperfusion injury (MIRI) in vitro and in vivo. But its detailed cardiac protection mechanism is still unclear. The MIRI mice model was established by ligating the left anterior descending branch (LAD) of the left coronary artery in C57BL/6 mice. Sixty C57BL/6 mice were randomly divided into four groups. CGA group and CGA + I/R group (each group n = 15) were gavaged with 30 mg/kg/day CGA for 4 weeks. Sham group and I/R group mice (each group n = 15) were administered equal volumes of saline. In vitro MIRI model was constructed by hypoxia and reoxygenation of HL-1 cardiomyocytes. The results showed that CGA pretreatment reduced myocardial infarction size and cTnT contents in serum, simultaneously reduced the levels of Lnc Neat1 expression and attenuated NLRP3 inflammasome-mediated pyroptosis in myocardial tissue. Consistent with in vivo results, the pretreatment of 0.2 μM and 2 μM CGA for 12 h in HL-1 cardiomyocytes depressed hypoxia/reoxygenation-induced Lnc Neat1 expression, NLRP3 inflammasome activation and pyroptosis. Lnc Neat1 shRNA transfection mediated by lentivirus in HL-1 cardiomyocytes significantly reduced activation of NLRP3 inflammasome and pyroptosis. Our findings suggest that CGA protects against MIRI by depressing Lnc Neat1 expression and NLRP3 inflammasome-mediated pyrotosis. Inhibiting the levels of Lnc Neat1 expression may be a therapeutic strategy for MIRI.

Abstract Background Foamy viruses (FVs) are retroviruses with unique replication strategies that cause lifelong latent infections in their hosts. FVs can also produce foam-like cytopathic effects in vitro. However, the effect of host cytokines on FV replication requires further investigation. Although interferon induced transmembrane (IFITMs) proteins have become the focus of antiviral immune response research due to their broad-spectrum antiviral ability, it remains unclear whether IFITMs can affect FV replication. Method In this study, the PFV virus titer was characterized by measuring luciferase activity after co-incubation of PFVL cell lines with the cell culture supernatants (cell-free PFV) or the cells transfected with pcPFV plasmid/infected with PFV (cell-associated PFV). The foam-like cytopathic effects of PFV infected cells was observed to reflect the virus replication. The total RNA of PFV infected cells was extracted, and the viral genome was quantified by Quantitative reverse transcription PCR to detect the PFV entry into target cells. Results In the present study, we demonstrated that IFITM1-3 overexpression inhibited prototype foamy virus (PFV) replication. In addition, an IFITM3 knockdown by small interfering RNA increased PFV replication. We further demonstrated that IFITM3 inhibited PFV entry into host cells. Moreover, IFITM3 also reduced the number of PFV envelope proteins, which was related to IFITM3 promoted envelope degradation through the lysosomal pathway. Conclusions Taken together, these results demonstrate that IFITM3 inhibits PFV replication by inhibiting PFV entry into target cells and reducing the number of PFV envelope.

Healthy T cells are polyclonal, while malignant T cells are developing via clonal expansion. Here authors show that T cell tumours could be eradicated by chimeric antigen receptor T cells targeting the T cell receptor (TCR) β-chain that is specific to malignant T cells, while healthy T cells using diverse TCR β-chains are spared.

In recent years, COVID-19 has spread across the whole world, and manpowered collection of pharyngeal samples undoubtedly increases the possibility of cross-infections. In this article, based on our previous fabricated soft manipulator (Cell Reports Physical Science, 2021, 2, 100600), we performed the COVID-19 sampling on real human volunteers by exploiting a pre-programmed unmanned system. The unmanned sampling system mainly includes a soft manipulator and a rigid motion platform, which are adjusted by pneumatic control box and the motor control modules, respectively. Drawn on the lead-through teaching method, the unmanned sampling of COVID-19 is realized by recording the applied pressure in soft manipulator and the feed motion of rigid platform. This research provides a potential approach for unmanned COVID-19 sampling, solving the risk of cross-infection during manual collection.

Duchenne muscular dystrophy (DMD) is a severe, progressive, and incurable X-linked disorder caused by mutations in the dystrophin gene. Patients with DMD have an absence of functional dystrophin protein, which results in chronic damage of muscle fibers during contraction, thus leading to deterioration of muscle quality and loss of muscle mass over time. Although there is currently no cure for DMD, improvements in treatment care and management could delay disease progression and improve quality of life, thereby prolonging life expectancy for these patients. Furthermore, active research efforts are ongoing to develop therapeutic strategies that target dystrophin deficiency, such as gene replacement therapies, exon skipping, and readthrough therapy, as well as strategies that target secondary pathology of DMD, such as novel anti-inflammatory compounds, myostatin inhibitors, and cardioprotective compounds. Furthermore, longitudinal modeling approaches have been used to characterize the progression of MRI and functional endpoints for predictive purposes to inform Go/No Go decisions in drug development. This review showcases approved drugs or drug candidates along their development paths and also provides information on primary endpoints and enrollment size of Ph2/3 and Ph3 trials in the DMD space.

ABSTRACT Foamy viruses (FVs) are complex retroviruses belonging to the Spumaretrovirinae subfamily of the Retroviridae family. In contrast to human immunodeficiency virus (HIV), another member of the Retroviridae family, FVs are nonpathogenic in their natural hosts or in experimentally infected animals. Prototype foamy virus (PFV) is the only foamy virus that can infect humans through cross-species transmission and does not show any pathogenicity after infection. Consequently, PFV is considered a safe and efficient gene transfer vector. Understanding the host proteins involved in the replication of PFV and the mechanism of interaction between the host and the virus might lead to studies to improve the efficiency of gene transfer. To date, only a few host factors have been identified that affect PFV replication. In the present study, we report that PFV infection enhances the promoter activity of SGK1 (encoding serum/glucocorticoid regulated kinase 1) via the Tas protein signaling pathway, and then upregulates the mRNA and protein levels of SGK1. Overexpression of SGK1 reduced PFV replication, whereas its depletion using small interfering RNA increased PFV replication. SGK1 inhibits PFV replication by impairing the function of the PFV Tas activation domain in a kinase-independent manner and reducing the stability of the Gag protein in a kinase-dependent manner. In addition, both human and bovine SGK1 proteins inhibit the replication of bovine foamy virus (BFV) and PFV. These findings not only improved our understanding of the function of SGK1 and its relationship with foamy viruses, but also contributed to determining the antiviral mechanism of the host. IMPORTANCE Foamy viruses can integrate into the host chromosome and are nonpathogenic in natural hosts or in experimentally infected animals. Therefore, foamy viruses are considered to be safe and efficient gene transfer vectors. Persistent infection of foamy viruses is partly caused by the restrictive effect of host factors on the virus. However, only a few cellular proteins are known to influence the replication of foamy viruses. In this study, we report that SGK1 inhibits the replication of prototype foamy virus by affecting the function of the transcription activator, Tas, and reducing the stability of the structural protein, Gag. These results will increase our understanding of the interaction between the virus and host factors, deepening our perception of host antiviral defenses and the function of SGK1, and could improve the gene transfer efficiency of foamy viruses.

Foamy viruses (FVs) are classified in the subfamily Spumaretrovirinae and bridge the gap between Orthoretrovirinae and Hepadnaviridae. FVs have strong cytopathic effects against cells cultured in vitro. However, they establish lifelong latent infections without evident pathology in the host. The roles of cellular factors in FV replication are poorly understood. To better understand this area, we determined the transcriptomes of HT1080 cells infected with prototype foamy virus (PFV) to measure the effect of PFV infection on the expression of cellular genes. We found that the level of RelB mRNA, a member of the nuclear factor‐κB (NF‐κB) protein family, was significantly decreased as a result of PFV infection, and this was further confirmed with real‐time PCR. Interestingly, overexpression of RelB reduced PFV replication, whereas its depletion using small interfering RNA increased PFV replication. This inhibitory effect of RelB results from diminished transactivation of the viral long terminal repeat (LTR) promoter and an internal promoter (IP) by viral Tas protein. Together, these data demonstrate that PFV infection downregulates the viral inhibitory host factor RelB, which otherwise restricts viral gene expression.

BackgroundParkinson’s disease (PD) is the second most common neurodegenerative disease. Long non-coding RNA (lncRNA) small nucleolar RNA host gene 14 (SNHG14) has been demonstrated as an important regulator in PD pathology. However, the functional mechanisms played by SNHG14 in PD remain largely unclear.MethodsWe used 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium (MPP+) to establish PD mouse and cell models. The levels of SNHG14, miR-214-3p, and Krüppel-like factor 4 (KLF4) were gauged by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot analysis. Cell viability and apoptosis were determined using the Cell Counting-8 Kit (CCK-8) assay and flow cytometry, respectively. The levels of inflammatory cytokines were evaluated by ELISA. The relationships among SNHG14, miR-214-3p, and KLF4 were confirmed by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.ResultsOur data indicated that SNHG14 was upregulated and miR-214-3p was downregulated in PD models. SNHG14 knockdown ameliorated MPP+-stimulated damage in SK-N-SH cells, as evidenced by the enhancement in cell viability and the suppression in cell apoptosis and pro-inflammatory cytokine production. Mechanistically, SNHG14 directly targeted miR-214-3p via binding to miR-214-3p, and SNHG14 knockdown protected SK-N-SH cell from MPP+-stimulated cytotoxicity by upregulating miR-214-3p. KLF4 was a direct target of miR-214-3p, and SNHG14 regulated KLF4 expression by acting as a miR-214-3p sponge. Furthermore, miR-214-3p overexpression alleviated MPP+-stimulated damage in SK-N-SH cells by downregulating KLF4.ConclusionOur current study first demonstrated the protective effect of SNHG14 knockdown on MPP+-stimulated cytotoxicity in SK-N-SH cells at least partially by targeting the miR-214-3p/KLF4 axis, illuminating a promising target for PD intervention and treatment.

Patients with nondipper hypertension are known to carry a high risk of cardiovascular complications. Vitamin D deficiency is associated with hypertension. Because vitamin D deficiency activates the renin–angiotensin–aldosterone system (RAAS), we hypothesized that this vitamin would interact with the RAAS to influence blood pressure (BP) in nondipper hypertensive patients. We performed a cross-sectional analysis of 1,007 outpatients with hypertension (HTN). Dipper and nondipper patterns were detected, and the two groups were matched for clinical, laboratory, 25-hydroxyvitamin D (25OHD) levels, and ambulatory blood pressure recording. Plasma renin activity (PRA), angiotensin II, and plasma aldosterone concentration (PAC) were assessed in 174 patients treated with calcium channel blockers or no medication. The mean 25OHD concentration in the entire study population was 12.3ng/dL, and the prevalence of vitamin D deficiency was 87.0%. Dipper and nondipper HTN were noted in 187 patients (24.6%) and 573 patients (75.4%). 25OHD levels were similar between nondipper and dipper HTN groups. Forward stepwise logistic regression analysis showed that BMI and age were independent predictors of nondipper HTN. Neither 25OHD levels nor RAAS components were included in the model. In correlation analyses, nocturnal decline of diastolic BP was positively associated with 25OHD levels and standing PRA (r = 0.152 p = 0.045, r = 0.165 p = 0.038, respectively). The present study showed that vitamin D deficiency was astonishingly prevalent in hypertensive subjects residing in Xinjiang, China. There may be a weakly association of nocturnal DBP decline with 25OHD levels and standing PRA levels. We found no association between vitamin D deficiency and nondipper HTN.

Membrane proteins of enveloped viruses have been reported to undergo palmitoylation, a post-translational modification often having a critical role in the function of these viral proteins and hence viral replication. In this study, we report that the foamy virus (FV) envelope (Env) glycoprotein is palmitoylated. Specifically, we found that bovine foamy virus (BFV) Env (BEnv) is palmitoylated at amino acid positions C58 and C59 by BDHHC3 and BDHHC20 in a DHHC motif-dependent manner. In addition, mutations C58S and C58/59S significantly decrease cell surface expression of BEnv, subviral particle (SVP) egress, and its membrane fusion activity, thus ultimately inhibiting BFV replication. The C59S mutation exerts a minor effect in this regard. Taken together, these data demonstrate that the function of BEnv in the context of BFV replication is under the regulation of palmitoylation.

The superior ability of soft robotic systems is their good adaptability to complicated external environments without damaging themselves and their surroundings. Dielectric elastomers (DEs) are known as artificial muscles for soft actuations; however, rigid frames are commonly required to sustain the prestretch, highly limiting flexibility designs. Moreover, under high actuation voltage, DEs are susceptible to electrical breakdowns. Furthermore, pure-soft actuators cannot sustain deformations under external loads. Therefore, based on the fiber-reinforced DE films, we develop a cylindrical freestanding electro-pneumatic DE actuator (EPDEA), which combines the advantages of pneumatic and electric actuators. The finite element model (FEM) simulation is also performed to study the combined deformations (a combination of elongation and bending) of EPDEAs. Due to fiber reinforcement, we introduce the mechanical anisotropies in DE films, and realize the large directional bending deformations (>180°) and output forces under the electro-pneumatic actuation. Fiber-jamming suits (FJSs) are simultaneously developed for the EPDEA to obtain the variable stiffness capability. The EPDEA with the FJS unit can hold the end position under a weight of 200 g (which is almost 4 times the weight of EPDEA). The effects of structural parameters and supporting pressure on the actuation and stiffness tuning the performance of EPDEA are also investigated.

Since publication of this paper, the authors have noticed an error in one of the images. In Fig. 2c, the graphs of c-Myc and CREB are incorrect. During image synthesis, these two images were confused with other images from the raw data. The error does not impact the conclusions of the article. The authors would like to apologize for any inconvenience this may have caused. This has been corrected in both the PDF and HTML versions of the Article. An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Under an applied voltage, dielectric elastomers (DEs) produce an actuation strain that is nonlinear, partly because of the material properties. In this study, an experimental characterization is conducted to evaluate how the ambient temperature and pre-stretch affected the actuation performance. For DEs with a pre-stretch of 2×2, an increase of temperature from −10°to 80°results in a variation in the actuation strain of more than 1700%. Low pre-stretched DEs are more susceptible to temperature change; while highly pre-stretched DEs are relatively insensitive to temperature, because in this case the energy conversion was dominated by mechanical stretching, rather than thermal conduction, during the actuation.

Viscoelasticity dissipates the mechanical energy, leading to a reduction of energy conversion efficiency in both dielectric elastomer (DE) actuators and generators. By measuring the uniaxial tension-recovery experiments of very-high-bond-based DE, this article quantitatively presents the effect of viscoelasticity on energy harvesting performance of DE generators. By employing a DE strip energy harvester with constant surface charge, an analytical model is established to calculate the generated electrical energy and energy conversion efficiency. Numerical results demonstrate that viscoelasticity has a significant influence on DE energy harvesting performance.

In this paper, we present a theoretical study about the effect of viscoelasticity on the electromechanical performance of a dielectric elastomer (DE) balloon. The thermodynamic dissipative model is given and the equation of motion is deduced by a free-energy method. It is found that when the balloon is only subject to the pressure or a static voltage, it may reach a state of equilibrium after the viscoelastic relaxation. When the static voltage exceeds a certain value, the balloon will never reach the equilibrium and be in failure eventually. When the voltage is sinusoidal, the balloon will resonate at multiple frequencies. The study result indicates that the natural frequency is independent on the viscoelasticity. However, the presence of viscoelasticity can reduce the amplitude and increase the mean stretch of the DE.

Cucumber grows with complex phenomena by changing its volume and shape, which is not fully investigated and challenges agriculture and food safety industry. In order to understand the mechanism and to characterize the growth process, the cucumber is modeled as a hydrogel in swelling and its development is studied in both preharvest and postharvest stages. Based on thermodynamics, constitutive equations, incorporating biological quantities, are established. The growth behavior of cucumber follows the classic theory of continuous or discontinuous phase transition. The mechanism of bulged tail in cucumber is interpreted by phase coexistence and characterized by critical conditions. Conclusions are given for advances in food engineering and novel fabrication techniques in mechanical biology.

Subject to a mechanical load or a voltage, a membrane of a dielectric elastomer deforms. As for the deformation mode, the dynamic performance and stability are strongly affected by how mechanical forces are applied. In the current study, by using the Euler-Lagrange equation, an analytical model is developed to characterize the dynamic performance of a homogeneously deformed viscoelastic dielectric elastomer under the conditions of equal-biaxial force, uniaxial force, and pure shear state, respectively. Numerical results are shown to describe the electromechanical deformation and stability. It is observed that the resonant frequency (where the amplitude-frequency curve peaks) has dependencies on the deformation mode, the level of mechanical load, and the applied electric field. When a dielectric elastomer membrane is subject to equal-biaxial force or pure shear state, it undergoes a nonlinear quasi-periodic vibration. An aperiodic motion of the dielectric elastomer system is induced by the boundary condition of a uniaxial force. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) feature nonlinear dynamics resulting from an electromechanical coupling. Under alternating voltage, the DE resonates with tunable performances. We present an analysis of the nonlinear dynamics of a DE as electromechanical resonator (DEER) configured as a pure shear actuator. A theoretical model is developed to characterize the complex performance under different boundary conditions. Physical mechanisms are presented and discussed. Chaotic behavior is also predicted, illustrating instabilities in the dynamics. The results provide a guide to the design and application of DEER in haptic devices. [ABSTRACT FROM AUTHOR]

The present study was aimed at investigating the detailed functions of atorvastatin, a lipid-lowering agent, in the pathogenesis of coronary slow flow (CSF), a clinical disease characterized by delayed angiographic coronary opacity without obstructive coronary disease. In the present study, we successfully identified isolated endothelial progenitor cells (EPCs) from the peripheral blood of patients with CSF. Their vascular endothelial growth factor-A (VEGFA) protein levels were determined using immunoblotting analyses. We determined cell viability using MTT assays, cell migration capacity using Transwell assays, and the angiogenic capacity using a tube formation assay. The target association between miR-221 and VEGFA was validated with a luciferase reporter assay. Atorvastatin treatment increased EPC VEGFA protein levels, proliferation, migration, and angiogenesis. miR-221 expression was down-regulated after atorvastatin treatment; miR-221 overexpression exerted an opposing effect to atorvastatin treatment on VEGFA protein, EPC proliferation, migration, and angiogenesis. The protective effects of atorvastatin treatment on VEGFA protein and EPCs could be significantly suppressed by miR-221 overexpression. miR-221 directly bound the VEGFA 3-UTR to inhibit its expression. In conclusion, atorvastatin improves the cell proliferation, migration, and angiogenesis of EPCs via the miR-221/VEGFA axis. Thus, atorvastatin could be a potent agent against CSF, pending further in vivo and clinical investigations. [ABSTRACT FROM AUTHOR]

For dielectric elastomers (DEs), the inherent viscoelasticity leads to a time-dependent deformation during actuation. To describe such a viscoelastic behavior, a constitutive model is developed by utilizing a combined Kelvin-Voigt-Maxwell (KVM) model. The established model captures both the initial jumping deformation and the following slow creeping. Subsequently, with an employment of VHB 4910 elastomer, experiments are performed to validate the viscoelastic KVM model. The results indicate a good agreement between the simulation and experimental data. Effect of the parameters in KVM model on the viscoelastic deformation of DEs is also investigated. [ABSTRACT FROM AUTHOR]

Viscoelasticity causes a time-dependent deformation and lowers the response speed and energy conversion efficiency of VHB-based dielectric elastomers (DEs), thus seriously restricting a wide range of applications of this otherwise versatile soft smart material. The viscoelastic deformation of a prestretched VHB film in a circular actuator configuration is studied both theoretically and experimentally. By adjusting the applied voltage, viscoelastic creep can be dispelled and an invariable strain is obtained by simulation. Subsequently, an experiment was designed to validate the simulation and the results indicate that a constant strain can be achieved by preprogramming the applied actuation voltage. [ABSTRACT FROM AUTHOR]

The electromechanical properties of dielectric elastomers (DEs) are strongly affected by the environmental factors, such as ambient temperature and humidity. In this paper, by employing the VHB 4910 elastomer, we carry out an experimental investigation on the temperature effect on the electromechanical properties of DEs, including the electromechanical breakdown and voltage-induced deformation. Two kinds of tension modes, i.e. equal-biaxial tension and unidirectional fiber-constrained state, are adopted in the experimental measurements. It is found that both the breakdown voltage and the breakdown electric field of VHB 4910 under equal-biaxial tension reduce gradually with the increasing temperature. For the VHB elastomer under unidirectional fiber-constrained state, the temperature does not show a monotonous effect on the electromechanical properties. Finally, effect of temperature on voltage-induced deformation of VHB 4910 is tested, and the results demonstrate that the electromechanical deformation initially increases and subsequently decreases as the temperature rises. [ABSTRACT FROM AUTHOR]

In this research, we carry out a modeling and experimental study on the performance of a VHB 4910 elastomer considering the humidity effect. Firstly, based on the uniaxial tension test of VHB 4910, it is concluded that humidity leads to a reduction of the shear modulus. Subsequently, the static electromechanical performance of VHB 4910 is explored, which implies that voltage-induced deformation increases gradually with the increasing humidity. Finally, by applying a sinusoidal voltage, the humidity effect on the resonance properties of the VHB 4910 elastomer is found to decrease the resonant frequency and augment the vibration intensity. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) generate a large deformation under the external stimulation, while the electromechanical performances are strongly affected by the dissipative properties, such as viscoelasticity and leakage current. In this article, the input electrical energy for actuation and dissipation of DEs during the process of viscoelastic creep is investigated by utilizing a deduced dissipative model. Effect of the ratio N between resistor-capacitor time constant and viscoelastic relaxation time on the dissipative performances of DEs is also considered. The total current from the battery, the leakage current, the electrical power density and the electrical energy density of DEs with different values of N are respectively exhibited. The dissipation of electrical energy induced by the electrodes resistance is also included and investigated. [ABSTRACT FROM AUTHOR]

Ionic electroactive polymer (iEAP) actuators have attracted great attention in the fields of micro-electromechanical systems and biomedicine due to their remarkably large strain under low-voltage stimulation. As actuation performance is mainly dominated by the electrochemical and electromechanical processes, the electrode layer and its structure are increasingly crucial to the actuators. In this research, we introduced a nanoporous carbon nanotube film with superior conductivity (1000–2000 S cm−1) as a cost-effective alternative electrode in fabricating iEAP actuators. The actuators were assembled by hot-pressing a Nafion/EMImBF4 electrolyte layer between two electrode films under vacuum conditions. Based on the developed porous hierarchal structure and superior electrical and mechanical properties of the electrode film, the actuators showed highly improved electrochemical and electromechanical properties and can operate controllably and durably under various voltage amplitudes and waveforms with a wide frequency range. The generated strain and stress reach up to 1.26% and 5.27 MPa, respectively, which are greater than the performances of the actuators based on polymer-supporting nano carbon electrodes. Once the voltage increases by 1 V, the strain and stress will increase by 0.336% and 1.407 MPa, respectively. The actuators can perform more than 20 000 cycles with an initial drop less than 20% in the operation stroke, showing a relatively durable and controllable cycle life. The newly developed actuators can be promising candidates for artificial muscles in academic interest and industrial applications. [ABSTRACT FROM AUTHOR]

Subject to a high voltage, leakage current and induced electrical energy dissipation inevitably occur during the actuation of dielectric elastomers (DEs). In this article, a theoretical model is developed to investigate the dissipative performance of DEs in dynamic actuation. Effects of three different actuation conditions, including DE materials’ viscoelasticity intensity, amplitude of applied voltage, and mechanical tensile force, are considered. Numerical calculations are employed to detect the dynamic dissipative performance of DEs including leakage current, electrical power density, and electrical energy density in certain vibrational periods. Leakage current and induced electrical energy dissipation are enhanced with the enlargement of amplitude of applied voltage and mechanical force, and are suppressed as the intensity of DEs’ viscoelastic creep increases. The electrical energy for dissipation and actuation is also analyzed and compared. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) are capable of large deformation under the actuation of applied voltage and sprayed charge. Actuation of DE under voltage control is prone to electromechanical instabilities, while the DE under charge control always survives from instabilities with sacrificing a large deformation. In this article, a novel actuation mode of steady electric field is proposed. By tuning applied voltage and sprayed charge during viscoelastic creep, an invariable electric field is generated. Such an actuation method can both avoid the occurrence of electromechanical instabilities and guarantee a large deformation in DE actuation. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) under pure shear state can generate the giant deformation without the pull-in and snap-through instabilities. The pure shear state is usually achieved by using fibers to constrain the deformation in an in-plane direction. Since the DEs cannot support the compressed stress, the instability of loss of tension (LT) may occur in the fiber-constrained direction as the voltage-induced Maxwell stress increases. In this article, by incorporating the effects of different values of tensile force, applied voltage (including both step and ramp voltages), prescribed constrained deformation and viscoelasticity intensity, a viscoelastic model is employed to explore the instability of LT of fiber-constrained DEs with analysis of the electromechanical deformation and stress evolution. [ABSTRACT FROM AUTHOR]

In this paper, based on the standard linear solid rheological model, a dynamics model of viscoelastic dielectric elastomers (DEs) is developed with incorporation of viscous damping effect. Numerical calculations are employed to predict the damping effect on the dynamic performance of DEs. With increase of damping force, the DEs show weak nonlinearity and vibration strength. Phase diagrams and Poincaré maps are utilized to detect the dynamic stability of DEs, and the results indicate that a transition from aperiodic vibration to quasi-periodic vibration occurs with enlargement of damping force. The resonance properties of DEs including damping effect are subsequently analyzed, demonstrating a reduction of resonant frequency and resonance peak with increase of damping force. [ABSTRACT FROM AUTHOR]

A dielectric elastomer is capable of large deformation under alternating electromechanical excitation. In this paper, several dynamic properties of a dielectric elastomer are investigated, in particular the effect of strain stiffening. A theoretical model is established that shows that the bias voltage affects the amplitude and the response waveform during vibration, a curve with the shape of a pinnacle. We also describe the underlying physical mechanism by considering the molecular chain length and cross-linking density of the material. A phase portrait is presented that reveals the transitional behavior of the dielectric elastomer as it switches between soft and stiffened vibration states. [ABSTRACT FROM AUTHOR]

Deformation in charge-controlled dielectric elastomer actuation eliminates pull-in instability, but the performance is affected by dissipative characteristics, such as viscoelasticity and leakage current. This letter focuses on the modeling of the dissipative performance in charge-controlled dielectric elastomer actuation. The effects of the initial surface charge and the ratios between viscoelastic relaxation time and resistor-capacitor time constant are investigated. By spraying charge to compensate the leakage and adjusting the surface charge, the viscoelastic relaxation is dispelled and the invariable deformation is tuned. The rate of spraying charge to suppress viscoelastic creep is determined by the difference between the value of the leakage current and the rate of the change of the surface charge. [ABSTRACT FROM AUTHOR]