Eversion and Retraction of a Soft Robot Towards the Exploration of Coral Reefs

Coral reefs are declining worldwide. Yet, critical information remains unknown about the basic biological, ecological, and chemical processes that sustain coral reefs because of the challenges to access their narrow crevices and passageways. A robot that grows through its environment would be well suited to this challenge as there is no relative motion between the exterior of the robot and its surroundings. In this work, we design and develop an eversion robot for operation underwater, show that existing models work for constrained passageways if external contacts are taken into account, and present a new model to describe the forces on the robot during retraction. We use ambient water to pressurize the robot and maintain a neutral buoyancy. The robot operates in open loop without any steering, but can rely on its compliance to conform to natural crevices and pathways in its environment. We demonstrate the mechanism of eversion and retraction for an underwater soft robot as a potential approach for future non-destructive exploration of coral reefs.