Towards Soft Steerable Vine Robots Using Actuating Polymers

Everting soft robots, or vine robots, can navigate delicate, constrained environments with minimal friction. These robots extend from the tip when pressurized, enabling forward motion, however, they require additional actuators to actively steer. Previous works have investigated the use of external magnetic fields, the integration of various pneumatic artificial muscles, and the use of tendon-driven mechanisms to enable active steering. Here, we present an alternative steering approach for vine robots based on the integration of a thermally actuating polymer, liquid crystal elastomer (LCE). We propose a design and fabrication approach to ensure localized bending of the robot and characterize the resulting steering capabilities, including the response time and the achievable bending angle as the pressure inside the robot is varied. The design consisted of independent LCE-heater units integrated at discrete locations along the robot body. When the LCE actuator was heated, the robot could achieve a wide range of bending angles from 8.5° to 57.0° by modulating the internal pressure from 14.89 to 2.76 kPa, respectively. The time required for the LCE to fully actuate was approximately 4 minutes. The performance suggested that soft steerable vine robots with actuating polymer can be used to navigate curved or branching environments.