Search

Dielectric elastomer generators (DEGs) based on silicone rubber composites have received considerable attention in recent years. However, the addition of traditional rigid dielectric fillers not only increases the modulus of composites but also leads to interface debonding between the filler and elastomer matrix under high stretching conditions, thereby limiting the energy harvesting performance. Here, gel-like ester group grafted butadiene rubber (GEBR) with a relatively low modulus was synthesized and used as a "soft filler" to enhance energy harvesting performance of PMVS-based DE composites. The GEBR filler with a high concentration of polar groups could lead to an increase in the dielectric constant of GEBR/PMVS composites by the introduction of interfacial polarizability and the improvement of dipole polarizability. Most notably, compared with TiO2 as the rigid filler, the combination of GEBR's deformability under stretching and strong interfacial interaction between the GEBR filler and PMVS matrix could effectively prevent weak interface formation under high strain conditions, and thus hinder the propagation of electrical treeing. As a result, benefiting from the GEBR filler with a low modulus, 5 vol% GEBR/PMVS DEG exhibits an excellent maximal energy density (65.4 mJ g−1) and outstanding power conversion efficiency (38.4%), achieving a high energy density at relatively low input mechanical force. This study presents a pioneering methodology to fabricate high-performance all-organic DE composites for DEGs through designing a soft dielectric filler with exceptional deformability under stretching. [ABSTRACT FROM AUTHOR]

To achieve dielectric elastomer generators (DEGs) with excellent energy harvesting performance and long life, electrode materials with high compliance, high electrical conductivity (EC), high stability of EC under high strain, and high durability are key. Nevertheless, the compliance of previously reported electrodes for DEGs still needs to be improved, and they cannot be repaired at room temperature after being damaged, inducing the trouble of disassembling the DEG device. In this study, a highly conductive supermolecule-based electrode material for DEGs was designed and prepared by synthesizing a polyborosiloxane supermolecule network (PBS-SN) matrix with multiple dynamic bonds followed by introduction of highly conductive carbon black (CB) and carbon grease (CG) into the PBS-SN matrix. Benefiting from the multiple dynamic bonds of the PBS-SN matrix and the introduction of appropriate content of a silicone oligomer (SO) with high chain mobility and plasticizing effect, the as-prepared CB/CG/PBS-SN electrode exhibits a high elongation at break (>1000%), high compliance, high self-healing efficiency of EC at room temperature (93% for 3 h), good recyclability (at least five times without performance reduction) and high durability (up to 10 000 cycles). Compared with a DEG using the commonly used CG electrode, the DEG using the CB/CG/PBS-SN electrode exhibits higher energy density, which is 60.9% higher than that of the former, and much higher than that reported in many previous studies. The excellent room temperature self-healing ability of the electrode can help the in situ repair of the DEG device, reducing the trouble of disassembling the device and improving the convenience of usage. [ABSTRACT FROM AUTHOR]

Dielectric elastomer (DE) materials suffer from high driving voltages and cracks or breaks during repetitive actuation cycles. New DE materials with a simultaneous high dielectric constant (ε′) and fast and efficient self-healing ability are in urgent need. Herein, we report a self-healable silicone DE by constructing a supramolecular network assembled by coordination bonds between carboxylated polymethylvinylsiloxane (PMVS-COOH) and FeCl3 as well as hydrogen bonds between carboxyl groups through introducing FeCl3 into PMVS-COOH. Both experimental results and density functional theory indicate that the Fe3+/COO− complex is formed and can further aggregate into clusters, which can simultaneously realize the crosslinking of PMVS-COOH and introduce interfacial polarization. Interestingly, the interfacial polarization largely increases with increasing FeCl3 content and FeCl3 can promote dipole polarization by disrupting some of the hydrogen bonds and releasing carboxyl groups when the FeCl3 content is higher than 5%, leading to a significant enhancement in ε′. The as-prepared PMVS-COOH/FeCl3 (SiR-Fe) DE with 8% FeCl3 shows comparatively high ε′ (12.3 at 104 Hz), much higher than that of the commercial silicone DE (∼2.7) or PMVS-COOH (6.1). Meanwhile, a self-healing efficiency of 99% in tensile strength and 100% in tensile toughness are achieved for SiR-Fe with 8% FeCl3 after being treated for 1 h at room temperature. This is ascribed to the high chain mobility of SiR-Fe and the robust supramolecular dynamic network resulting from the combination of coordination bonds and hydrogen bonds. It is demonstrated that SiR-Fe can be effectively used as a dielectric elastomer sensor. And it is promising that this highly efficient self-healable SiR-Fe DE with high ε′ finds applications especially in biological and medical fields. [ABSTRACT FROM AUTHOR]

Dielectric elastomers are referred to as artificial muscles because of their excellent properties. However, the need for high operating voltage limits their practical application. A reduction of the operating voltage can be achieved with novel elastomers offering intrinsically high electromechanical sensitivity. In this work, slide-ring materials with a necklace-like molecular structure are prepared as dielectric elastomer materials. These slide-ring materials are found to exhibit high dielectric constants, low elastic moduli, and high electromechanical sensitivity due to their special structural characteristics. Barium titanate particles modified by γ-methacryloxypropyl trimethoxy silane (KH570) are incorporated into the slide-ring materials to further improve the actuated performance of the slide-ring materials. A high actuated strain (26%) at a relatively low electric field (12 kV mm−1) is obtained on the circular membrane actuator without any pre-strains, much more excellent than those of other dielectric elastomers reported in the literature. In addition, an obviously larger displacement is achieved by the slide-ring composite than that of commercial dielectric elastomer VHB 4910 on a cone-type actuator at the same electric field. These results demonstrate that our research might help to establish a new synthetic route to high performance dielectric elastomers. [ABSTRACT FROM AUTHOR]

We report the design and preparation of a separated-structured all-organic dielectric elastomer (DE) with large actuation strain under ultra-low voltage and high mechanical strength. Based on the protonic-conductivity mechanism of gelatin, a novel organic conductive filler with high dielectric constant and low elastic modulus was prepared by mixing gelatin and glycerol (GG). The separated structured DE was prepared by spraying a solution of GG into the multiple layers of thermoplastic polyurethane elastomer (TPU) nonwoven fabric by electrospinning, followed by hot pressing under vacuum. The densely packed TPU nonwoven fabric not only ensures the good mechanical strength of GG/TPU DE, but also separates GG filler and stops the formation of the GG continuous phase, preventing the formation of a conducting path under an exerted electric field. The novel GG filler considerably increases the dielectric constant and decreases the elastic modulus of the GG/TPU DE. As a result, the as-prepared DE exhibits good mechanical strength and 5.2% actuation strain at a very low electric field (0.5 kV mm−1). To the best of our knowledge, the required electric field for the same actuation strain is the lowest compared to other DE reported in the literature. Because all components in this composite are organic and biocompatible, this study offers a new method for preparing a DE with large actuation strain at low electric fields for its application in biological and medical fields, in which a low electric field is required. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators (DEAs) can lead to surprisingly large deformations by applying an electric field. The biggest challenge for DEAs is to get a large actuated strain at a low electric field. Herein, a novel approach was used to largely improve the actuated strain at a low electric field of a thermoplastic polyurethane (TPU) dielectric elastomer (DE) by introducing polyethylene glycol (PEG) oligomer into the matrix. The dielectric constant (εr) of TPU was obviously increased by adding PEG due to the combined effect of the increase in the interfacial polarization ability of TPU/PEG blends by the ionic conductivity of PEG and the increase in dipole polarization ability of TPU chain segments by the disruption of hydrogen bonds of TPU chains. Meanwhile, the elastic modulus (Y) of TPU was obviously decreased due to the plasticizing effect of PEG on TPU. The simultaneous increase in εr and decrease in Y resulted in a 7500% increase in actuated strain at a low electric field (3 V μm−1) by adding PEG. The actuated strain (5.22% at 3 V μm−1) is considerably higher than that of other DEs at the same electric field reported in the literatures. Our work provides a simple and effective method to largely improve the actuated strain at a low electric field of a DE, facilitating the application of DE in biological and medical fields. [ABSTRACT FROM AUTHOR]

A novel dielectric composite with high dielectric constant (k), low dielectric loss, low elastic modulus and large actuated strain at a low electric field was prepared by a simple, low-cost and efficient method. The graphene oxide nanosheet (GO)-encapsulated carbon nanosphere (GO@CNS) hybrids were fabricated for the first time via π-π interaction and hydrogen bonding interaction by simply mixing the CNS and GO suspension. The assembly of GO@CNS hybrids around rubber latex particles was realized by hydrogen bonding interaction between carboxylated nitrile rubber (XNBR) and GO@CNS hybrids during latex compounding. The thermally reduced GO (RGO)@CNS/XNBR composites were then obtained from GO@CNS/XNBR by vulcanization and in situ thermal reduction, resulting in the formation of a segregated filler network. The results showed that k at 103 Hz obviously increased from 28 for pure XNBR to 400 for the composite with 0.75 vol% of the hybrids because of the formation of a segregated filler network and the increased interfacial polarization ability of the hybrids after in situ partial thermal reduction. Meanwhile, the composite with 0.75 vol% of the hybrids retained low conductivity (10-7 S m-1), resulting in low dielectric loss (<0.65 at 103 Hz). In addition, the elastic modulus only mildly increased with the addition of 0.75 vol% of the hybrids, retaining the good flexibility of the composites. More interestingly, the actuated strain at 7 kV mm-1 obviously increased from 2.69% for pure XNBR to 5.68% for the composite with 0.5 vol% of RGO@CNS, and the actuated strain at a lower electric field (2 kV mm-1) largely increased from 0.23% for pure XNBR to 3.06% for the composite with 0.75 vol% of RGO@CNS, which is much higher than that of other dielectric elastomers reported in previous studies, facilitating the application of the dielectric elastomer in biological and medical fields, where a low electric field is required. [ABSTRACT FROM AUTHOR]