Silicone-layered waterproof electrohydraulic soft actuators for bio-inspired underwater robots

Area of Science:

• Robotics
• Materials Science
• Fluid Mechanics

Background:

• Electrohydraulic soft actuators offer advantages for bio-inspired underwater robots, including large deformations, fast responses, and high efficiency.
• A key limitation is the requirement for high voltages, restricting their use in aquatic environments and hindering underwater robot development.

Purpose of the Study:

• To develop and demonstrate silicone-layered electrohydraulic soft actuators capable of operating underwater.
• To enable the construction of bio-inspired underwater robots and various soft robotic devices.

Main Methods:

• Fabrication of bending and linear electrohydraulic soft actuators with silicone layers acting as insulators.
• Characterization of actuator performance, including bending angle, linear strain, and blocked force at high voltages (10 kV).
• Integration of actuators into diverse soft robotic platforms such as fish robots, ray robots, and grippers for underwater testing.

Main Results:

• Silicone-layered actuators successfully demonstrated underwater actuation, functioning at depths near the water surface.
• Bending actuators achieved a 39.0° bending angle and 9.6 mN blocked force; linear actuators showed 6.6% contraction strain and 956.1 mN blocked force at 10 kV.
• Implemented robotic devices exhibited expected functionalities, with swimming robots reaching locomotion speeds up to 31.2 mm/s and a gripper performing a pick-and-place task.

Conclusions:

• The developed silicone-layered electrohydraulic soft actuators effectively overcome the high-voltage limitation for underwater operation.
• This technology holds significant potential for advancing bio-inspired underwater robotics and broader soft robotics applications.