A bi-stable soft robotic bendable module driven by silicone dielectric elastomer actuators: design, characterization, and parameter study

In this paper, we present a novel concept for a planar soft robotic module actuated by smart artificial muscles. The structure consists of a flexible backbone capable of continuously bending along a plane, and having a rigid plate connected to its top. The actuation is provided by an antagonist-agonist pair of artificial muscle fibers, consisting of silicone-based rolled dielectric elastomer actuator (RDEA) membranes connected to the rigid top plate. When actuated via high voltage, the RDEAs expand and, in turn, cause the structure to bend along a desired direction. The novel prototype concept is described in detail first, and systematic parameter studies are conducted afterwards by means of a physics-based model. Then, an experimental prototype is manufactured and tested, with the aim of validating the dependency of the bending angle performance on the system design parameters. We demonstrate that the bending angle is strongly affected by the choice of the flexible beam geometry, as well as the RDEAs mounting points. It is found that, for some combinations of parameters, the buckling instability of the beam can be suitably triggered by the RDEAs, resulting in large bending angles up to 25°. This feature also allows to keep the robot deformed without supplying any electric power. In contrast, parameters corresponding to mono-stable configurations result in a maximum bending angle of 11° only.