Development of a Liquid-Metal-Enhanced Continuum Joint with Variable Stiffness Capability for Flexible Endoscopy

The robot-assisted flexible access surgery, represented by the emerging robot-assisted flexible endoscopy (FE) and natural orifice transluminal endoscopic surgery, requires flexible and compliant manipulators. Achieving the necessary capacity for addressing diverse surgical scenarios with variable stiffness while maintaining an appropriate balance remains a significant challenge. This study introduces a novel liquid-metal-based continuum joint with variable stiffness capability to tackle these challenges. It comprises the central helical continuum joint, a low-melting-point alloy layer, and a water circulation layer. In contrast to other materials-based variable stiffness methods, an innovative approach has been proposed that combines electric heating and water heating while actively cooling by water to achieve a faster rigid-flexible transformation process. Characterization experiments have demonstrated that the proposed approach achieves a high rigid-flexible conversion ratio of up to 51.