A Novel Distal Hybrid Pneumatic/Cable-Driven Continuum Joint with Variable Stiffness Capacity for Flexible Gastrointestinal Endoscopy

The robot-assisted flexible access surgery represented by the emerging robot-assisted flexible endoscopy (FE) and natural orifice transluminal endoscopic surgery demands flexible and continuum manipulators instead of the rigid and straight instruments in the traditional minimally invasive surgery (MIS). These flexible manipulators are required to advance through the tortuous and narrow anatomic paths via natural orifices for dexterous diagnostic examination and therapeutic operations. Therefore, developing flexible endoscopic manipulators with the capacity of snake-like movements for flexible access and variable stiffness regulation for operations to address these flexible access surgical difficulties is demanding but remains challenging. To address such challenges, herein, it is proposed that a novel distal continuum joint based on the hybrid pneumatic and cable-driven approach achieves variable stiffness capacity, excellent bending characteristics in both flexible and rigid states, satisfactory motion consistency and shape-locking ability during the rigid-flexible transition, and relatively high loading capacity for flexible gastrointestinal endoscopic robots. Characterization experiments validate these performances, and phantom and ex vivo experiments have been performed to demonstrate the feasibility and effectiveness for FE. The presented method demonstrates an effective and practical approach to enabling continuum robots with both flexible access and tunable stiffness capacity and supports a convenient extension for MIS applications.