Assembly and Characterization of a DE Actuator Based on Polymeric Domes as Biasing Element

Abstract

Dielectric elastomer (DE) technology opens up the possibility of constructing novel lightweight and energy-efficient mechatonic systems, whose design can be tailored to several applications. Numerous types of DE actuator (DEA) configurations, capable of high-force, high-speed, and high-stroke, have been presented in the recent literature. One relevant example is represented by membrane DEAs. This type of actuator consists of a DE film pre-loaded with a mechanical bias. In case the biasing element shows a negative slope (i.e., stiffness) in its force-displacement characteristic, the stroke of the resulting DEA can be significantly magnified. Conventional negative-stiffness biasing systems are based on pre-compressed metal beams, thus they appear as unsuitable for miniaturization to the meso- or micro-scale, as well as for the design of completely flexible actuators for wearable and soft robotics applications. To overcome those issues, a new, novel, full polymer-based DEA configuration is introduced in this work. The core element is the biasing system, which is based on a compliant silicone dome. This type of bias presents a negative stiffness region within its mechanical characteristic; thus, it can serve as a flexible alternative to metal-based biasing systems. It will be shown how the force-displacement characteristic of the dome can be geometrically tuned to match the ones of the DE. In this way, a large actuation stroke can be achieved with a full polymer-based design. After discussing system design and manufacturing, the actuator element is assembled. Finally, experimental stroke characterization is performed.