Electromechanical Stability of Dielectric Elastomer Using Electric Energy Density Function With Variable Dielectric Constant

Dielectric elastomer(DE) is a kind of promising material bearing excellent activate properties including large deformations (up to 380%), high energy densities (up to 3.4 J/g), high efficiency, high responsive speed, good reliability and durability. Thus the DE actuator, sensors and energy harvester is widely used in the field of aeronautics and smart bionics. When an electric field is applied on the compliant electrodes of the dielectric elastomers, the polymer shrinks along the electric field and expands in the transverse plane. In consequence, the electric field becomes higher. This kind of positive feedback may cause the elastomer to thin down, resulting in an electromechanical stability. An analysis on the electromechanical stability of dielectric elastomer using arbitrary free-energy function with constant dielectric constant has been presented in Suo’s papers. In many research on the electromechanical stability analysis of DE actuator, DE’s dielectric constant is assumed to be a constant. This is only the truth if the dielectric elastomer undergoing limited deformation. Actually, a typical dielectric elastomer is a kind of crosslinked polymer. The structural symmetry of the macromolecular, the crosslinking degree, along with the tensile deformation can affect the dielectric permittivity enormously. For dielectric elastomers with higher crosslinking degree, or higher degree of molecular structural symmetry, its permittivity is relatively low. In addition, stretching can guide the macromolecule to be arranged in order, this can increase the intermolecular forces and reduce the activities of polar group, as a results, the dielectric constant will decrease. However, if the crosslinking degree is low and the deformation is well below the extension limit, the molecular units in the polymers can be polarized as freely as in a polymeric liquid. In this case the corresponding permittivity is unaffected by the deformation. Recent experimental research results also proved that the dielectric permittivity of dielectric elastomer changed while undergoing large deformation. According to Pelrine, the dielectric constant of the DE film is variable and it is a function of the area increase ratio which depends on stretch ratio. In this paper, approach for the electromechanical stability of a dielectric elastomer having variable dielectric constant is developed. The critical breakdown electric field is obtained. Simulation results proved that the prestretching process can enhance remarkably the electromechanical stability of dielectric elastomer. These results agree well with the experimental data and can be used as guidances in the design and fabrication of dielectric elastomer actuators.

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Preparation and Characterization of CCTO/PDMS Dielectric Elastomers with High Dielectric Constant and Low Dielectric Loss

Polymers ◽

10.3390/polym13071075 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1075

Author(s):

Wenqi Wang ◽

Guanguan Ren ◽

Ming Zhou ◽

Wei Deng

Keyword(s):

Mechanical Properties ◽

Dielectric Constant ◽

Elastic Modulus ◽

Dielectric Properties ◽

Dielectric Loss ◽

Electric Field ◽

Polymer Material ◽

Dielectric Elastomer ◽

Electroactive Polymer ◽

Dielectric Elastomers

Dielectric elastomer (DE) is a type of electric field type electroactive polymer material that can produce greater deformation under the action of an electric field and has a faster recovery speed. It has the advantages of high energy density, large strain, low quality, and commercialization, and has become the most widely concerned and researched electroactive polymer material. In this study, copper calcium titanate (CCTO) particles with a large dielectric constant were selected as the filling phase, and a silicone rubber (PDMS) with better biocompatibility and lower elastic modulus was used as the matrix to prepare CCTO/PDMS, which is a new type of dielectric elastomer material. The structure of the dielectric elastomer is analyzed, and its mechanical properties, dielectric properties, and driving deformation are tested. Then, KH550, KH560, and KH570 modified CCTO is used in order to improve the dispersibility of CCTO in PDMS, and modified particles with the best dispersion effect are selected to prepare dielectric elastomer materials. In addition, mechanical properties, dielectric properties, and driving deformation are tested and compared with the dielectric elastomer material before modification. The results show that as the content of CCTO increases, the dielectric constant and elastic modulus of the dielectric elastomer also increase, and the dielectric loss remains basically unchanged at a frequency of 100 Hz. When the filling amount reaches 20 wt%, the dielectric constant of the CCTO/PDMS dielectric elastomer reaches 5.8 (100 Hz), an increase of 120%, while the dielectric loss at this time is only 0.0038 and the elastic modulus is only 0.54 MPa. When the filling amount is 5 wt%, the dielectric elastomer has the largest driving deformation amount, reaching 33.8%. Three silane coupling agents have been successfully grafted onto the surface of CCTO particles, and the KH560 modified CCTO has the best dispersibility in the PDMS matrix. Based on this, a modified CCTO/PDMS dielectric elastomer was prepared. The results show that the improvement of dispersibility improves the dielectric constant. Compared with the unmodified PDMS, when the filling content is 20 wt%, the dielectric constant reaches 6.5 (100 Hz). Compared with PDMS, it has increased by 150%. However, the improvement of dispersion has a greater increase in the elastic modulus, resulting in a decrease in its strain parameters compared with CCTO/PDMS dielectric elastomers, and the electromechanical conversion efficiency has not been significantly improved. When the filling amount of modified CCTO particles is 5 wt%, the dielectric elastomer has the largest driving deformation, reaching 27.4%.

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Analysis of the Novel Strain Responsive Actuators of Silicone Dielectric Elastomer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.47-50.298 ◽

2008 ◽

Vol 47-50 ◽

pp. 298-301 ◽

Cited By ~ 9

Author(s):

Li Wu Liu ◽

Jiu Ming Fan ◽

Zhen Zhang ◽

Liang Shi ◽

Yan Ju Liu ◽

...

Keyword(s):

Finite Element ◽

Electric Field ◽

Large Deformation ◽

Deformation Theory ◽

High Efficiency ◽

High Energy ◽

Dielectric Elastomer ◽

Dielectric Elastomers ◽

Large Strains ◽

The Novel

The acrylic acid and silicone are common dielectric elastomer materials. These actuators have shown excellent activate properties including large strains up to 380% and high energy densities up to 3.4 J/g, high efficiency, high responsive speed , good reliability and durability, etc. When a voltage is applied on the compliant electrodes of the dielectric elastomers, the polymer shrinks along with the electric field and expands in the plain area which erects the orientation of the line. In this paper, we synthesize a novel silicone dielectric elastomer with high dielectric constant, large strain and high force output. Pre-strain and certain driving electric field are applied on the novel silicone film, respectively. The strain responsing to the Maxwell stress is measured. Using the large deformation theory of finite element method to simulate the deformable behavior of materials, the simulation results agree with the experiment. The coupling effect of the mechanics and electric fields applied on the electrode of the dielectric elastomers is inverstigated. The finite element simulation of large deformation theory can be used to describe the dielectric elastomers materials large deformation that induced by the static electric field.

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Improved dielectric constant and energy density of P(VDF-HFP) composites using NBT-xST (x=0, 0.10, 0.26) whiskers

Journal of Advanced Dielectrics ◽

10.1142/s2010135x18500406 ◽

2018 ◽

Vol 08 (06) ◽

pp. 1850040 ◽

Cited By ~ 1

Author(s):

Xuefan Zhou ◽

Lu Wang ◽

Guoliang Xue ◽

Kechao Zhou ◽

Hang Luo ◽

...

Keyword(s):

Energy Efficiency ◽

Dielectric Constant ◽

Energy Storage ◽

Energy Density ◽

Electric Field ◽

High Performance ◽

Volume Fraction ◽

High Energy ◽

High Energy Density ◽

Surface Modified

The high-performance energy-storage dielectric capacitors are increasingly important due to their wide applications in high power electronics. Here, we fabricated a novel P(VDF-HFP)-based capacitor with surface-modified NBT-[Formula: see text]ST ([Formula: see text], 0.10, 0.26) whiskers, denoted as Dop@NBT-[Formula: see text]ST/P(VDF-HFP). The influences of ST content, fillers’ volume fraction and electric field on the dielectric properties and energy-storage performance of the composites were investigated systematically. The results show that the dielectric constant monotonously increased with the increase of ST content and fillers’ volume fraction. The composite containing 10.0 vol% NBT-0.26ST whiskers possessed a dielectric constant of 39 at 1[Formula: see text]kHz, which was 5.6 times higher than that of pure P(VDF-HFP). It was noticed that the D-E loops of the composites became thinner and thinner with the increase of ST content. Due to the reduced remnant polarization, the composite with 5.0 vol% NBT-0.26ST whiskers achieved a high energy density of 6.18[Formula: see text]J/cm3 and energy efficiency of approximately 57% at a relatively low electric field of 200[Formula: see text]kV/mm. This work indicated that NBT-0.26ST whisker is a kind of potential ceramic filler in fabricating the dielectric capacitor with high discharged energy density and energy efficiency.

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High energy storage density of poly(vinylidene fiuoride) bulk nanocomposites at low electric field induced by giant dielectric constant ceramic nanopowders

Ceramics International ◽

10.1016/j.ceramint.2018.08.119 ◽

2018 ◽

Vol 44 ◽

pp. S181-S185 ◽

Cited By ~ 5

Author(s):

Zhuo Wang ◽

Tian Wang ◽

Yujia Xiao ◽

Wenwen Nian ◽

Haonan Chen

Keyword(s):

Dielectric Constant ◽

Energy Storage ◽

Electric Field ◽

High Energy ◽

Energy Storage Density ◽

Storage Density ◽

Giant Dielectric ◽

Giant Dielectric Constant ◽

High Energy Storage Density ◽

High Energy Storage

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Soft, tough, and fast polyacrylate dielectric elastomer for non-magnetic motor

Nature Communications ◽

10.1038/s41467-021-24851-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Li-Juan Yin ◽

Yu Zhao ◽

Jing Zhu ◽

Minhao Yang ◽

Huichan Zhao ◽

...

Keyword(s):

High Performance ◽

Crosslinking Agent ◽

High Energy ◽

Dielectric Elastomer ◽

High Energy Density ◽

Dielectric Elastomers ◽

Dielectric Elastomer Actuators ◽

Response Bandwidth ◽

Electrically Actuated ◽

Soft Actuators

AbstractDielectric elastomer actuators (DEAs) with large electrically-actuated strain can build light-weight and flexible non-magnetic motors. However, dielectric elastomers commonly used in the field of soft actuation suffer from high stiffness, low strength, and high driving field, severely limiting the DEA’s actuating performance. Here we design a new polyacrylate dielectric elastomer with optimized crosslinking network by rationally employing the difunctional macromolecular crosslinking agent. The proposed elastomer simultaneously possesses desirable modulus (~0.073 MPa), high toughness (elongation ~2400%), low mechanical loss (tan δm = 0.21@1 Hz, 20 °C), and satisfactory dielectric properties ($${\varepsilon }_{{{{{{\rm{r}}}}}}}$$ ε r = 5.75, tan δe = 0.0019 @1 kHz), and accordingly, large actuation strain (118% @ 70 MV m−1), high energy density (0.24 MJ m−3 @ 70 MV m−1), and rapid response (bandwidth above 100 Hz). Compared with VHBTM 4910, the non-magnetic motor made of our elastomer presents 15 times higher rotation speed. These findings offer a strategy to fabricate high-performance dielectric elastomers for soft actuators.

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Long-lifetime All-polymer Artificial Muscle Transducers

MRS Proceedings ◽

10.1557/proc-1271-jj03-01 ◽

2010 ◽

Vol 1271 ◽

Cited By ~ 12

Author(s):

Roy Kornbluh ◽

Annjoe Wong-Foy ◽

Ron Pelrine ◽

Harsha Prahlad ◽

Brian McCoy

Keyword(s):

Electric Field ◽

Salt Water ◽

Mechanical Strain ◽

Performance Testing ◽

Dielectric Elastomer ◽

Operating Conditions ◽

Peak Performance ◽

Dielectric Elastomers ◽

High Humidity ◽

Operational Conditions

AbstractThe dielectric elastomer, a particularly attractive type of electroactive polymer, uses commercial polymers such as acrylic and silicone elastomers. The technology has been limited in application by perceived lifetime issues. By addressing several lifetime issues, lifetimes of more than one million cycles, and in some cases beyond ten million cycles, were achieved with a variety of transducer configurations (including operation in generator mode) under a variety of operating conditions (including high humidity). Dielectric elastomers can produce maximum actuation strains of more than 100% and specific energy density exceeding that of known electric-field induced technology. Performance testing for dielectric elastomer actuators has typically been for peak-performance or “over-driven” conditions with short operational lifetimes (typically 100s or 1000s of cycles), particularly under conditions such as high humidity. By minimizing electric field and mechanical strain concentration factors, long lifetimes (>1 million cycles) with acrylic transducers were achieved with actuation strains as great as 40% areal strain (and up to 100% areal strain in generator mode). Actuators in a dry environment had an almost 20x increase in lifetime over actuators at ambient humidity (about 50% RH) at the same driving field conditions. Long actuation lifetimes were also achieved in a 100% RH environment and when fully submerged in salt water at reduced operating strain and field. In 100% RH, lifetimes of several million cycles were achieved at 4% strain. In underwater operation, 6 out of 11 actuators survived for >10 million cycles with an electric field limited to 32 MV/m and approximately 2% strain. The demonstrated lifecycle improvements are applicable to a variety of uses of dielectric elastomers, including haptic interface devices, pumps (implantable and external), optical positioners, and “artificial muscles” to replace small damaged muscles. Continued improvements in materials, actuator design, and packaging, combined with management of operational conditions as described here, should support new practical application of this promising technology.

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Enhanced dielectric properties and thermostability in polyimide composites with core-shell structured polyimide@BaTiO3 nanoparticles

High Performance Polymers ◽

10.1177/0954008321993526 ◽

2021 ◽

pp. 095400832199352

Author(s):

Wei Deng ◽

Guanguan Ren ◽

Wenqi Wang ◽

Weiwei Cui ◽

Wenjun Luo

Keyword(s):

Dielectric Constant ◽

Dielectric Loss ◽

Energy Density ◽

Breakdown Strength ◽

In Situ Polymerization ◽

Dielectric Materials ◽

High Energy ◽

Amic Acid ◽

High Energy Density ◽

Core Shell

Polymer composites with high dielectric constant and thermal stability have shown great potential applications in the fields relating to the energy storage. Herein, core-shell structured polyimide@BaTiO3 (PI@BT) nanoparticles were fabricated via in-situ polymerization of poly(amic acid) (PAA) and the following thermal imidization, then utilized as fillers to prepare PI composites. Increased dielectric constant with suppressed dielectric loss, and enhanced energy density as well as heat resistance were simultaneously realized due to the presence of PI shell between BT nanoparticles and PI matrix. The dielectric constant of PI@BT/PI composites with 55 wt% fillers increased to 15.0 at 100 Hz, while the dielectric loss kept at low value of 0.0034, companied by a high energy density of 1.32 J·cm−3, which was 2.09 times higher than the pristine PI. Moreover, the temperature at 10 wt% weight loss reached 619°C, demonstrating the excellent thermostability of PI@BT/PI composites. In addition, PI@BT/PI composites exhibited improved breakdown strength and toughness as compared with the BT/PI composites due to the well dispersion of PI@BT nanofillers and the improved interfacial interactions between nanofillers and polymer matrix. These results provide useful information for the structural design of high-temperature dielectric materials.

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