Bio-inspired multi-mode finger mechanism based on Miura-ori unit equivalent linkages

Origami structures, characterized by predefined crease patterns and configurable properties, offer valuable insights for designing reconfigurable mechanisms. Inspired by diverse grasping states of the human finger and multi-mode characteristics of the Miura-ori unit, this paper proposes a novel finger mechanism capable of four distinct single degree-of-freedom (DOF) motion modes. Each mode corresponds to a distinct finger state, characterized by two interphalangeal joints that are either rotatable or nonrotatable. First, the Miura-ori unit equivalent linkage (PFSFL, plane-symmetric flat-deployable spherical four-bar linkage) is introduced, and its multi-mode characteristics are analyzed through an approach based on dual quaternions. Next, the finger mechanism is constructed by coupling specific links and joints of two PFSFLs, and its multi-mode kinematics are systematically demonstrated. Three such fingers are integrated with an orthogonal Bricard linkage to develop a multi-mode grasping mechanism. A pneumatically actuated, 3D printed gripper based on this mechanism is fabricated, and experimentally confirms its multi-mode grasping capability. The results demonstrate the potential of the proposed finger mechanism for developing reconfigurable grippers or hands with enhanced flexibility, adaptability, and multi-task capability.