Development of a Compliant Fractal Robotic Gripper for Light Load Applications

This study developed of a compliant fractal robotic gripper designed for light-load applications. Conventional rigid grippers often struggle with object variability, fragility, and unstructured environments, motivating the need for adaptive and compliant end-effectors. To address these limitations, the proposed gripper integrates fractal-inspired geometry with compliant mechanism principles to achieve passive adaptability using a single actuator. The gripper was designed using a three-level binary fractal structure with flexure and notch-type compliant hinges, enabling deformation-based conformity to a wide range of object geometries. Finite Element Analysis was conducted to evaluate stress distribution and deformation behavior, thereby guiding iterative design refinement before fabrication. The physical prototype was fabricated using fused deposition modeling, employing thermoplastic polyurethane for the compliant fingers and polylactic acid for rigid structural components. Actuation was achieved through a rack-and-pinion mechanism driven by a stepper motor and controlled via an Arduino-based open-loop control system. Performance evaluation was carried out using standardized metrics for grasping force, stability, and adaptability. Experimental results showed an average maximum settling grasping force of 8.987 N with high repeatability. Slip resistance tests demonstrated improved load capacity with the addition of silicone pads, achieving a maximum of 7.048 N and increased friction coefficients. Adaptability tests confirmed the gripper’s ability to securely grasp objects of varying shapes, sizes, and levels of fragility without causing damage. The results demonstrate that combining fractal geometry and compliant mechanisms provides a practical and low-cost approach for developing versatile robotic grippers suitable for light load applications.