Assembly and characterization of a DE-actuator based on polymeric domes as biasing element

Dielectric elastomer (DE) technology opens up the possibility of constructing novel lightweight and energy-efficient actuators, whose design can be tailored to several applications. Numerous actuator configurations, capable of high-force, high-speed, or high-stroke, have been presented in the recent literature. Some types of DE-actuators (DEAs), namely membrane DEAs, need to be pre-loaded by a mechanical biasing system in order to generate a stroke. To achieve a large deformation with such membrane DEAs, a mechanical biasing element showing a negative slope (i.e., stiffness) in its force-displacement characteristic needs to be used. Typically, negative-slope biasing systems for DEAs are realized by pre-compressed thin metal beams. Such metal elements, however, do not lend themselves to miniaturization to the meso- and micro-scale. Additionally, metal components unavoidably affect the stiffness of the overall actuator system, thus making it not suitable for applications such as wearables and soft-robotics. To overcome those issues, a new type full polymer-based DEA element is presented in this work. This type of DEAs can be used as elementary taxels in cooperative arrays of micro-actuators. In order to achieve a completely flexible structure without losing the benefits of negative-slope biasing systems, a compliant silicone-based dome element is proposed as a novel biasing system. By tuning the dome geometry, it is possible to affect its force-displacement characteristic and, in turn, to design a large-stroke DEA. After discussing the novel compliant actuator concept, the assembly process will be presented in details. Finally, experimental validation of the proposed design will be carried out. It is shown that polymeric domes are well suited for constructing large-stroke DEAs, which is an important step towards the construction of a flexible and cooperative micro-array system.