A Novel Soft Gripper Featuring a Self-Bending Contraction Actuator (SBCA) with Reconfigurable Bending Characteristics

Soft pneumatic actuators are widely used in robotic manipulation due to their compliance and adaptability; however, their performance is typically fixed at the fabrication stage, limiting their suitability for applications requiring task-specific tuning. This paper presents a reconfigurable self-bending contraction actuator (SBCA) that enables post-fabrication adjustment of mechanical behaviour through interchangeable internal reinforcing elements. The proposed design introduces novel end fittings that allow rapid, non-destructive insertion and replacement of reinforcing rods, transforming the actuator from a fixed-function component into a tunable system. Four reinforcing rod geometries are designed and experimentally evaluated to investigate the influence of stiffness distribution on actuator performance. Results show that reinforcement geometry significantly affects both bending curvature and force transmission, with the proposed configurations achieving up to 77° bending at 2 bar and a maximum fingertip force of 4.73 N. A 25.42% increase in bending angle and a 10% increase in force are observed relative to a baseline configuration. Beyond performance improvements, the study establishes a direct relationship between internal structural variation and actuator output, highlighting a controllable trade-off between bending curvature and force generation. This provides a practical framework for tuning actuator behaviour without redesign or reconstruction. A three-finger soft gripper integrating the proposed SBCA is developed and validated through grasping experiments on objects with varying geometries and mechanical properties, demonstrating robust and adaptive manipulation. The proposed approach advances SBCA design from fixed-performance actuators toward reconfigurable and application-adaptable soft robotic systems.