Gripping, Catching, and Conveying with a Soft, Toroidal Hydrostat

This work describes how a toroidal hydrostat can be used to perform three functions found in both living and engineered systems: gripping, catching, and conveying. We first demonstrate a gripping mechanism that uses the inversion characteristic of the toroid to encapsulate and grip onto objects under a uniform hydrostatic pressure. Using this mechanism, we demonstrate gripping forces ranging from 1-80 N, depending (in a predictable way) on the geometry and material 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 store mechanical energy and drive a rapid acceleration to capture moving objects out of the air. Finally, we show how the toroidal topology can be exploited to construct a soft conveying mechanism that continuously inverts and passes objects through its center—serving a similar function to that of esophageal peristalsis, while eliminating the requirement of a lubricated interface. In general, we show that the use of inflatable topological structures comprising soft polymeric films is a promising approach to designing soft robotic actuators with novel, bio-inspired functionality.