Origami-Based Robotic Gripper for Transporting Solids with Liquids

In the field of aquaculture and aquatic organism management, there is a need to transport both liquids and solids simultaneously. For instance, when dealing with fry or delicate organisms, it is preferable to transport them together with water, without removing them from their aquatic environment. However, accomplishing this task with a robot requires complex control mechanisms to account for the water flow generated when moving containers. Additionally, when pouring water, precise calculations and careful pouring techniques are necessary to determine the exact location where the water should be delivered. To address these challenges, this study proposes a gripper that can deform its shape underwater according to the shape of the container. The gripper utilizes a cylindrical shell with a Kresling structure, which is a folding structure capable of transforming a cylinder through compression. In this research, we analyze the conditions required for the gripper to transport water and investigate how the gripper's performance is affected by the number of folds. The design of the cylindrical shell is based on the condition of filling the center of the cylinder after deformation. To enhance underwater usability, the gripper incorporates a locking mechanism instead of relying on external actuators. As a result, we have successfully developed a gripper capable of transporting both liquids and solids using only vertical movements. To evaluate the gripper's performance, two experiments were conducted. The first experiment assessed the sealing ability of the gripper, which revealed a water leakage of 7 g per minute. In the second experiment, it was confirmed that the gripper can simultaneously transport solids with liquids using only vertical movements of the robot arm.