A detailed overview on interface design and control in polymer based composite dielectrics for energy storage applications.

Dielectric elastomers are of interest for actuator applications due to their large actuation strain, high bandwidth, high energy density, and their flexible nature. If future dielectric elastomers are to be used reliably in applications that include soft robotics, medical devices, artificial muscles and electronic skins, there is a need to design devices that are tolerant to electrical and mechanical damage. In this paper, we provide the first report of self-healing of both electrical breakdown and mechanical damage in dielectric actuators using a thermoplastic methyl thioglycolate modified styrene-butadiene-styrene (MGSBS) elastomer. The self-healing functions are examined from the material to device level by detailed examination of the healing process, and characterisation of electrical properties and actuator response before and after Complete Manuscript

Dielectric elastomers have the capability to be used as transducers for actuation and energy harvesting applications due to their excellent combination of large strain capability (100-400%), rapid response (10 s), high energy density (10-150 kJ m ), low noise, and lightweight nature. However, the dielectric properties of non-polar elastomers such as dielectric permittivity ε , breakdown strength E , and dielectric loss ε ″, need to be enhanced for real world applications. The introduction of polar groups or structures into dielectric elastomers through covalently bonding is an attractive approach to 'intrinsically' induce a permanent polarity to the elastomers, and can eliminate the poor post-processing issues and breakdown strength of extrinsically modified materials, which have often been prepared by incorporation of fillers. This review discusses the chemical methods for modification of dielectric elastomers, such as hydrosilylation, thiol-ene click chemistry, azide click chemistry, and atom transfer radical polymerization. The effects of the type and concentration of polar groups on the dielectric and mechanical properties of the elastomers and their performance in actuation and harvesting systems are discussed. State-of-the-art developments and perspectives of modified dielectric elastomers for deformable energy generators and transducers are provided.

Engineering materials and devices can be damaged during their service life as a result of mechanical fatigue, punctures, electrical breakdown, and electrochemical corrosion. This damage can lead to unexpected failure during operation, which requires regular inspection, repair, and replacement of the products, resulting in additional energy consumption and cost. During operation in challenging, extreme, or harsh environments, such as those encountered in high or low temperature, nuclear, offshore, space, and deep mining environments, the robustness and stability of materials and devices are extremely important. Over recent decades, significant effort has been invested into improving the robustness and stability of materials through either structural design, the introduction of new chemistry, or improved manufacturing processes. Inspired by natural systems, the creation of self‐healing materials has the potential to overcome these challenges and provide a route to achieve dynamic repair during service. Current research on self‐healing polymers remains in its infancy, and self‐healing behavior under harsh and extreme conditions is a particularly untapped area of research. Here, the self‐healing mechanisms and performance of materials under a variety of harsh environments are discussed. An overview of polymer‐based devices developed for a range of challenging environments is provided, along with areas for future research.

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The actuation and energy-harvesting performance of dielectric elastomers are strongly related to their intrinsic electrical and mechanical properties. For future resilient smart transducers, a fast actuation response, efficient energy-harvesting performance, and mechanical robustness are key requirements. In this work, we demonstrate that poly­(styrene-butadiene-styrene) (SBS) can be converted into a self-healing dielectric elastomer with high permittivity and low dielectric loss, which can be deformed to large mechanical strains; these are key requirements for actuation and energy-harvesting applications. Using a one-step click reaction at room temperature for 20 min, methyl-3-mercaptopropionate (M3M) was grafted to SBS and reached 95.2% of grafting ratios. The resultant M3M–SBS can be deformed to a high mechanical strain of 1000%, with a relative permittivity of εr = 7.5 and a low tan δ = 0.03. When used in a dielectric actuator, it can provide 9.2% strain at an electric field of 39.5 MV m–1 and can also generate an energy density of 11 mJ g–1 from energy harvesting. After being subjected to mechanical damage, the self-healed elastomer can recover 44% of its breakdown strength during energy harvesting. This work demonstrates a facile route to produce self-healing, high permittivity, and low dielectric loss elastomers for both actuation and energy harvesting, which is applicable to a wide range of diene elastomer systems.

While the fascinating field of soft machines has grown rapidly over the last two decades, the materials they are constructed from have remained largely unchanged during this time. Parallel activities have led to significant advances in the field of dynamic polymer networks, leading to the design of three‐dimensionally cross‐linked polymeric materials that are able to adapt and transform through stimuli‐induced bond exchange. Recent work has begun to merge these two fields of research by incorporating the stimuli‐responsive properties of dynamic polymer networks into soft machine components. These include dielectric elastomers, stretchable electrodes, nanogenerators, and energy storage devices. In this Minireview, we outline recent progress made in this emerging research area and discuss future directions for the field.

The majority of polymers are electrical and thermal insulators, with an electrical conductivity in the range of 10 -14 ~ 10 -18 S/cm, and thermal conductivity of 0.1~0.4 W/mK. In order to create electrically active and thermally conductive polymers and composites, a number of strategies have been investigated. The current state of the art technology is to apply hybrid filler systems in polymers, i.e., to combine different types of fillers with different dimensions, in order to facilitate the formation of interconnected conducting network and to enhance the electrical, thermal, mechanical, and processing properties synergistically. The dispersion and interfacial interaction between fillers and polymers determine the final properties of polymer composites. By tailoring polymer-filler interactions both thermodynamically and kinetically, the selective localisation of fillers in polymer blends can enhance the electrical conductivity at a low percolation threshold. The percolation threshold can be further reduced by selectively dispersing fillers at the interface of co-continuous polymer blends. Moreover, the selective localisation of different types of fillers in different cocontinuous phases can result in multiple functionalities, such as high electrical conductivity, thermal conductivity or electromagnetic interference shielding. In this review, we have discussed the latest progresses towards the development of electrically 2 active and thermal conductive polymer composites, and highlight the technical challenges and future research directions.