A Rigid-Foldable Kirigami-Inspired Metamorphic Mechanism With Programmable Motion Modes and Self-Locking.

Compact metamorphic mechanisms capable of multifunctionality, especially geometric-constraint-induced changes in motion mode and intrinsic self-locking without sustained actuation, are valuable for engineering deployable and adaptive robotic systems. This paper presents a rigid-foldable, kirigami-inspired metamorphic parallel mechanism composed solely of revolute joints. Based on screw theory, we establish a unified kinematic model that systematically characterizes the four distinct configurations and their corresponding motion modes, including one uniaxial twisting motion, two coupled translations (lateral-vertical and longitudinal-vertical), and a self-locking state consistent with the motion characteristics of the rigid-foldable kirigami. The analysis reveals that the mechanism can switch among the four motion modes by reconfiguring the geometric constraints through changes in the programming pattern of the four actuated joints, without reassembly of the kinematic structure. The proof-of-concept prototype and experimental tests validate motion-mode switching and the passive structural rigidity of the tested energy-free self-locking configuration. This work demonstrates a way to encode functional adaptability directly into robot body design, reducing reliance on complex actuation and control systems. Such principles have broad implications for scalable, energy-efficient systems in fields ranging from robotics and aerospace structures to biomedical devices.