A Biomimetic Underwater Soft Robot Inspired by Cephalopod Mollusc

This letter presents a biomimetic underwater soft robot design with novel propulsion and maneuvering mechanisms. The robot design took inspirations from cephalopod molluscs. The proposed robot comprises a soft mantle structure with multiple built-in soft actuators, which could deform to provide steering and maneuverability for underwater locomotion. Smart sensors are embedded into the soft mantle to provide real-time feedback to the controller. Underwater thrust is generated by a novel vortex-based soft tail mechanism also inspired by molluscs. The tail mechanism incorporates an electric motor sealed inside a continuum chamber, and rotational motion from the motor is transmitted to the soft-bodied tentacles, which generate a vortex to produce thrust. The resulting soft robot is incorporated in a seamless body, while both propulsion and steering are generated by soft-body deformation. To investigate the novel vortex-based biomimetic propulsion generation mechanism, an analytical model was developed to capture the relation between input motor speed and the resulting thrust force. The entire robot was fabricated using 3-D-printing and soft-material molding. The fabricated robot components and the assembled system were both validated through experiments. The results show that the mollusk-inspired robot could achieve underwater maneuverability by bending the four actuators, and the measured results match well with the proposed analytical mode. The proposed design could easily be repeated by anyone with access to a consumer-grade 3-D printer, enabling a wide range of biomimetic robot enthusiasts to investigate in the new mechanism for underwater propulsion and maneuvering.