A Doughnut Shaped Soft Gripper Based on 4D Printed Hydrogels

Soft grippers have recently been implemented to various applications due to their flexibility and compliance. They are conventionally actuated by electric and pneumatic systems. However, it is difficult to apply electric- and pneumatic-driven grippers to underwater applications thanks to the lack of waterproof ability. In this paper, we propose a doughnut shaped soft gripper based on four dimensional (4D) printing of hydrogels. The 4D printed hydrogels is capable of deforming when exposing to water stimuli. According to the property analysis of 4D printed hydrogels, such as deformation and force calibration, design parameters of the doughnut shaped gripper was determined. Underwater handling experiments were successfully conducted using the proposed soft gripper for grasping various objects with different shapes.