Progress in the design and modifications of dielectric elastomers has offered numerous effective techniques to improve their electrically induced actuation response. The actuation behaviour improves due to changes in electromechanical properties that eventually signifies the adjustments in the aspects of the structure of elastomer. This report aims to insight into the role of intrinsic structure on the electromechanical properties, considering the influences of pre-strain, fillers, and chemical modification techniques to enhance actuation performance. The aspects of structure namely, molecular structure, crosslink density, micropores, and interfacial characteristics are focused to reaffirm their relationship with the dielectric and mechanical properties of the elastomer. Thus, the effects of considered modification techniques on properties are discussed in the context of their impacts on structural parameters. These efforts together so identify the key challenges and opportunities in a complete understanding of structure-property relationships to improve actuation behaviour. Indeed, this may serve as a report on important information and focus required to obtain flexible dielectrics with desired electromechanical properties. 

Review on the Role of Intrinsic Structure on Properties of Dielectric Elastomers for Enhanced Actuation Performance

We present a compression sensor based on a strain-sensitive carbon black-silicone composite cast on top of a printed circuit board with interdigitated electrodes. This results in a very sensitive and soft capacitive compression sensor not requiring a structured dielectric or compliant electrodes. We show how the optimal loading of carbon black to maximize the sensitivity depends on the type of carbon black and the stiffness of the silicone matrix. The optimal quantity of carbon black leads to a high sensitivity of 252% for an input force of 10 N (this corresponds to an input pressure of 17 kPa), without stiffening the silicone matrix or increasing the viscoelastic losses noticeably. The fabrication process of the sensors is much simpler than that of other soft capacitive sensors, and unlike carbon black-silicone resistive sensors, these capacitive sensors do not exhibit time-dependent impedance creep. They can be made thick without affecting their base capacitance or sensitivity, leading to compliant and conformable sensing interfaces suitable for a variety of applications, such as robotic tactile sensors.

A Skin-Like Soft Compression Sensor for Robotic Applications.

Dielectric elastomer is a kind of attractive artificial muscle with fast and reversible deformation excited by applied voltages. Typical dielectric elastomers suffer from low dielectric breakdown strength, which limits the achievable electro-actuation performance. We report that the introduction of surface-modified ZrO2 nanoparticles in dielectric elastomer (poly(styrene-b-butyl acrylate-b-styrene)) can significantly increase the dielectric breakdown strength. We highlight that the surface modifier molecules for ZrO2 nanoparticles should be designed to have an oligomeric chain compatible with the elastomer matrix to relieve the entropy loss of the elastomer chains. Thus, good dispersion of the nanoparticles can be achieved and the modulus is mildly increased. As a result, the maximum electro-actuation area strain is increased by a factor of 2.0 (from 19.1% to 37.8%), and the maximum energy density by a factor of 9.2 (from 5.96 kJ/m3 to 55.15 kJ/m3) by adding 1.7 vol% ZrO2 of 8 nm. 

Significantly enhancing electro-actuation performance of dielectric elastomer with ZrO2 nanoparticles

Due to their feature of the conversion from electrical to mechanical energy under an applied electric field, dielectric elastomers (DEs) have been widely adopted in smart devices. However, the significant electro-actuated property of DEs is always obtained under a giant driving electric field, which raises a potential safety hazard and limits their practical application range. Moreover, the traditional strategy of regulating the flexibility of DEs via physical swelling effect would result in an undesired plasticizer leakage and an irreversible reduction in both electromechanical stability and lifetime. Herein, a typical heterogeneous multi-layered polydimethylsiloxane (PDMS)-based DE composite was prepared by solution blending and the layer-by-layer casting method. Through synchronously introducing the high-permittivity BaTiO3 and the plasticizer dimethyl silicone oil in the middle layer, both the dielectric and mechanical property of the composite are effectively regulated. Not only the interlayered mechanical mismatch is eliminated but also the problem of plasticizer leakage is optimized through this reasonable structural design. The maximum electro-actuated strain obtained in the sandwiched DE composite was as large as 24.25% under 60 V/ μm, which is 338.52% higher than that of pristine PDMS. Furthermore, the composite exhibits the largest driving strain (58.31%) near its breakdown electric field of 77.82 V/ μm. Therefore, this study provides a promising route for the preparation of advanced DE composite with an improved low-field electro-actuated property.

Enhanced electro-actuation property of heterogeneous multi-layered polydimethylsiloxane-based dielectric elastomer composites

The improved low‐field electro‐actuation of dielectric elastomer composites regulated by entirely‐inorganic
 
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Enhanced Electromechanical Properties of Three-Phased Polydimethylsiloxane Nanocomposites via Surface Encapsulation of Barium Titanate and Multiwalled Carbon Nanotube with Polydopamine

Yan-ting Zhang

Papers

Enhanced Electromechanical Properties of Three-Phased Polydimethylsiloxane Nanocomposites via Surface Encapsulation of Barium Titanate and Multiwalled Carbon Nanotube with Polydopamine