Recent progress in the development of dielectric elastomer materials and their multilayer actuators

Dielectric elastomers (DEs) have emerged as one of the most promising artificial muscle technologies, due to their exceptional properties such as large actuation strain, fast response, high energy density, and flexible processibility for various configurations. Over the past two decades, researchers have been working on developing DE materials with improved properties and exploring innovative applications of dielectric elastomer actuators (DEAs). This review article focuses on two main topics: recent material innovation of DEs and development of multilayer stacking processes for DEAs, which are important to promoting commercialization of DEs. It begins by explaining the working principle of a DEA. Then, recently developed strategies for preparing new DE materials are introduced, including reducing mechanical stiffness, increasing dielectric permittivity, suppressing viscoelasticity loss, and mitigating electromechanical instability without pre-stretching. In the next section, different multilayer stacking methods for fabricating multilayer DEAs are discussed, including conventional dry stacking, wet stacking, a novel dry stacking method, and micro-fabrication-enabled stacking techniques. This review provides a comprehensive and up-to-date overview of recent developments in high-performance DE materials and multilayer stacking methods. It highlights the progress made in the field and also discusses potential future directions for further advancements.