Design and Development of a Soft Actuator for a Robot Inspired by the Octopus Arm

The octopus arm presents peculiar features, like the capability of bending in all directions, producing fast elongations, and varying its stiffness. Such features are very attractive from a robotics point of view. In the octopus, these unique motor capabilities are given by the peculiar muscular structure of the octopus arm, named muscular hydrostat, that creates a sort of antagonistic mechanism between different muscle fibres and reduce the contraction requirements for the single muscle. By taking inspiration from this, we propose the design of a robot arm completely soft and compliant, composed of silicone muscles that can contract and that are arranged according to the anatomy of the octopus arm. The contractile units are built with EAP (Electro-Active Polymer) technologies, with a particular geometry that increases the contraction range and force. Contraction tests on prototypes of the contracting units show a very good similarity with a theoretical model and support the possibility of building the whole robotic octopus-like arm.