SoJel -A 3D printed jellyfish-like robot using soft materials for underwater applications

Mass manufactured, biologically inspired soft robots are needed for safe robot-animal interactions. The key challenges are the design and manufacture of high-performance robots that meet stringent requirements in ocean environments. This work describes a 92% 3D-printed jellyfish-inspired soft robot, SoJel, which uses soft polymers for the bell and sensors. We show how slight variations in geometry affects the swimming performance of the robot, which demonstrates the need for advanced or custom-made 3D printers that avoid the difficulties in realizing controlled geometries by using traditional molding and casting techniques. The design reproduces important kinematic patterns of natural jellyfish, like the bell bending angle, actuation duty cycle, and bell ki-nematics. This work builds on previous generations of jellyfish-inspired robots that employed various types of actuators, but is largely polymer based, so it avoids metallic components that are susceptible to corrosion in the ocean. The realized cost of transport and vertical swimming height of robots powered by coiled nickel-titanium actuators are comparable to previous designs, however, the present robots have advantages in ease of design and manufacturing. A variety of soft robots and flexible structures can potentially be fabricated using this design principle. Flexible 3D-printed soft sensors enable us to determine the bending angles for motion estimation and control. Energy harvesting from water oscillation or free vibration is demonstrated using a twistron harvester and a piezoelectric composite integrated into the robot, which can be used for powering electronics, such as a LED for display and communication.