Design of a soft and autonomous biomimetic micro-robotic fish

Abstract

This paper discusses the design of a flexible micro robotic fish that takes advantage of the energy saving feature of fish. The body of the fish is made of soft material with embedded electromagnets. It has a flexure link made of polyimide. Carbon-fiber reinforced composite material sandwiches the flexible link at four locations, allowing the four rigid links to be connected by a flexure joint. Nd-Fe-B magnets and planar coils are secured to the top of the composite material. The entire structure, including Li-ion battery and electronics, is embedded within polydimethylsiloxane (PDMS) sheets. It is then cut into the shape of a fish. The propagating muscle activity pattern is achieved by activating the electromagnets that correspond to each muscle group. The fish has polyvinylidene-fluoride-trifluoroethylene (PVDF-TrFE) piezoelectric polymer sensors on its surface to measure the local flow pressure. When it senses vortices, the fish automatically turns off the actuator so that its body wave can be passively generated by interaction with the oncoming flow of water. The power generated for positive work can be stored as elastic energy and then used for negative work, thus saving energy. The system is driven at its natural frequency to minimize energy consumption. Future generations of this microbotic fish could be deployed for underwater oil exploration and environmental monitoring.