Fish locomotion studied using an active-swimming soft-robotic model

By attaching soft robotic actuators (pneunets, ‘PN’) on a flexible passive foil, we constructed an active swimming model for fish locomotion called the ‘pneufish’. Pneunets are a series of hollow, connected chambers, molded from silicone rubber (Dragon skin 20, Smooth-On Inc., Easton, PA 18042, USA). When pressure is increased, each chamber expands and pushes against its neighboring chambers, resulting in a net lengthening and curvature of the PN. We assembled several pneufish and suspended them in a recirculating flow tank attached to an ATI 6-axis force-torque sensor. We measured thrust, lateral forces, and amplitude of trailing edge oscillation, investigating the swimming performance of the model at a variety of frequencies, flow speeds, foil stiffnesses, and air pressures. Results revealed the pneufish generates positive thrust at several parameter combinations, and while stiffness and activation frequency are important parameters, the interaction of the two are more important. Additionally, we have expanded the model from a simple two-pneunet apparatus (duo-pneufish) to a four-pneunet system consisting of two consecutive PNs on each side of the foil (quad-pneufish), and plan future experiments to evaluate the performance of this multi-segmented system that is more fish-like.