Improved Silicone Fish Tail Actuator With Variable Stiffness

Abstract

In a continuation of research presented at The University of Maryland Undergraduate Research Day, this work will document improvements on a fish-inspired robot actuator. Bio-inspired robotics is an interdisciplinary field offering advantages that diversify robot designs and improve functionality. Incorporating soft robotics techniques into bio-inspired designs expands the potential of new robots. A common research subject is fish-inspired robots, due to the several possibilities of experimentation. A fish’s naturally flexible body and reaction to the hydrodynamics of its environment provide useful inspiration for robots of similar design. In the question of improving the efficiency of robot performance in water, it can be seen in nature that several fish such as tuna adjust their swimming behaviors through tunable musculature. Prior research has observed muscle stiffness to impact swimming efficiency. This study aims to develop a silicone fishtail capable of variable stiffening. Previous experimentation resulted in a molding process, producing a thick prototype fin with cavities in which stiffening material is placed and the air vacuumed out - stiffening the fin. This work details the refinement of this process to create a fin that further meets the design specifications. The tail must be 150 millimeters wide at the tip and 10 millimeters thick. The new design process introduced a higher-quality silicone rubber, and a more in-depth preparation process, including a vacuum chamber. The new mold designs are easily adjustable to 3D print cavities of more complex geometries. Furthermore, the new molding process improved the assembly and overall fin aesthetic. The internal cavities were successfully compressed after attaching the fin to a 4.5-volt combined vacuum and pump. Further design includes quantitatively measuring this stiffness and performance in a flow.