Design of a bidirectional compliant gripper for robotic object manipulation

This study presents the design and development of a monolithic compliant gripper with bidirectional actuation, enabling both active grasping and full release within a single structural unit. To address these directional constraints commonly observed in conventional compliant mechanisms, the design incorporates a flexure-based cartwheel hinge that provides symmetric deformation and enhanced orientation adaptability. The gripper geometry is obtained through topology optimization to maximize material efficiency and mechanical advantage. Finite-element analysis and experimental validation confirm that the 3D-printed structure (30 g) achieves substantial bidirectional displacement under a 5 N input force. Performance testing demonstrates stable grasping, with successful manipulation of cubic objects at inclination angles up to 40° and pyramidal objects up to 50°. The integration of the cartwheel hinge enables more pronounced bidirectional motion and increased rotational capability, with a hinge thickness of 0.3 mm allowing rotation exceeding 90°, thereby improving grasping adaptability. Additionally, the gripper employs a modular structural design that allows rapid scaling from a two-finger pinch to a four-finger wrap. This system provides a lightweight and versatile solution for complex robotic manipulation tasks without the need for hardware redesign.