High-Velocity, Pressure-Driven Eversion for Rapid Vine Robots

Vine robots are an emerging class of soft, pneumatic robots that are characterized by everting tip extension and thin, tubular walls. This mechanism of tip-extension is found in a variety of organisms, including branched proboscis of ribbon worms and the micron-scale, penetrating stylets of jellyfish stinging cells. Past studies have solely focused on modeling extension during pressurization in the quasistatic regime, despite the ability of these robots to grow faster than 50m/s with accelerations greater than 336 m/s/s. In this study, we create a dynamic growth model for high-speed, thermoplastic polyurethane vine robot bodies and verify the model experimentally. We found three key results: i) the vine robot bodies experience rate-dependent damping which increases linearly during isometric scaling of the vine diameter and wall thickness; ii) the upper-limit of vine speed in terms of diameters/sec is scale invariant; and iii) efficiency increases nonlinearly with decreasing thickness and increasing diameter. Our work provides a basic understanding of the dynamic movement of vine robots and similar eversion mechanisms found in nature, opening the door to new application areas.