Dielectric elastomer actuators with granular coupling

So-called 'hydrostatically coupled' dielectric elastomer actuators (HC-DEAs) have recently been shown to offer new opportunities for actuation devices made of electrically responsive elastomeric insulators. HC-DEAs include an incompressible fluid that mechanically couples a dielectric elastomer based active part to a passive part interfaced to the load, so as to enable hydrostatic transmission. Drawing inspiration from that concept, this paper presents a new kind of actuators, analogous to HC-DEAs, except for the fact that the fluid is replaced by fine powder. The related technology, here referred to as 'granularly coupled' DEAs (GC-DEAs), relies entirely on solid-state materials. This permits to avoid drawbacks (such as handling and leakage) inherent to usage of fluids, especially those in liquid phase. The paper presents functionality and actuation performance of bubble-like GC-DEAs, in direct comparison with HC-DEAs. For this purpose, prototype actuators made of two pre-stretched membranes of acrylic elastomer, coupled via talcum powder (for GC-DEA) or silicone grease (for HC-DEA), were manufactured and comparatively tested. As compared to HC-DEAs, GC-DEAs showed a higher maximum stress, the same maximum relative displacement, and nearly the same bandwidth. The paper presents characterization results and discusses advantages and drawbacks of GC-DEAs, in comparison with HC-DEAs.