Bio-inspired design of soft mechanisms using a toroidal hydrostat

Biology is replete with soft mechanisms of potential use for robotics. Here, we report that a soft, toroidal hydrostat can be used to perform three functions found in both living and engineered systems: gripping, catching, and conveying. We demonstrate a gripping mechanism that uses a tubular inversion to encapsulate objects within a crumpled elastic membrane under hydrostatic pressure. This mechanism produces gripping forces that depend predictably upon the geometric and materials properties of the system. We next demonstrate a catching mechanism akin to that of a chameleon's tongue: the elasticity of the membrane is used to power a catapulting inversion process (approximate to 400 m/s(2)) to capture flying objects (e.g., a bouncing ball). Finally, we demonstrate a conveying mechanism that passes objects through the center of the toroidal tube (similar to 1 cm/s) using a continuous inversion -eversion process. The hybrid hard-soft mechanisms presented here can be applied toward the integration of soft functionality into robotic systems.