Meet the Robotic Manta Ray that is Wireless, Speedy, and Temperature-Resistant

Perhap some of you will remember Mr. Ray, the Manta Ray who acts as an underwater teacher and sometime schoolbus in the 2003 hit Disney movie Finding Nemo. Inspired by the Manta Ray’s soft body and flexible flapping wings of this incredible animal, a great development in the field of bioengineering was made by the engineers Tiefeng Li and Zhilong Huang in the College of Aeronautics and Astronautics of ZJU. The new bionic fish design could lead to lifelike robots that can explore the ocean, monitor water quality, and discover new creatures without disturbing them.

Specifications for the roboray, the fast-moving soft electronic fish:

 Length: 9.3 cm (18.5 cm including its tail)

 Weight: 90 g

 Maxium Speed with battery: 6 cm/s

 Maxium Speed without load: 13.5 cm/s

 Temperature range: 0-74 °C

 Water depth range: 0-200 m (deeper range remains to be tested)

 Tilted view of the fish showing the onboard system for power and remote control

Thanks to the counterintuitive design on the actuation of dielectric elastomer-driven muscle with surrounding water used as the ground end electrode, this robot can move quickly through the water. The outer layer of this fish is covered by soft silicone and an electrode connects with the hydrogel inside. The hydrogel is positively charged with applied voltage, while water outside the robot has negatively charged electrons. The attractions between the positive gel inside and the negative water outside would squeeze the body in between, flattening it original curvous structures on fins and bending them slightly upward. When the voltage from the inner electrode is removed, the pulling force is lost and the original configuration is restored. With the regular pulse of the electricity, the fins will flap up and down like wings.

This soft electronic fish possesses several notable attributes, including wireless mobility, transparency, endurance, and temperature tolerance. International experts on soft robotics have applauded the clever propulsion system design. Jun Shintake, an engineer at École Polytechnique Fédérale de Lausanne in Switzerland, who has used such actuators in soft robotic fish but was not involved in this research, praised the design:“For researchers, it is common sense that an actuator of this kind has to be paired with at least two electrodes. Li et al. had the bright idea of using the surrounding water as one side,”  Shintake talked to a reporter from Science magazine. “A clever, multimaterial integration and design strategy. It’s a very elegant demonstration—one that will further propel the field of soft robotics—no pun intended!” said Jennifer Lewis, a materials engineer at Harvard University who worked on the octobot.