A Novel Cable-Driven Variable-Stiffness Manipulator With Teeth-Engagement Structure for Transoral Surgery

As one of the minimally invasive surgeries (MIS), transoral robotic surgery (TORS) has garnered sustained interest for the treatment of pathological tissue, such as oropharyngeal tumors. Flexible manipulators employed in transoral surgeries necessitate the variable-stiffness capabilities to perform diverse tasks. Specifically, the manipulator must flexibly navigate through natural orifices to reach the target site and subsequently enhance the stiffness to provide a stable platform for surgical instrument manipulation. However, most existing flexible surgical manipulators have relatively small stiffness variation ratio and long transition time between flexible and rigid states. In this letter, we proposed a novel cable-driven variable-stiffness flexible manipulator with teeth-engagement structure to address such challenges. The proposed manipulator has an 18-mm diameter and provides four channels for forceps, electric knife, water/gas, and CMOS camera. Experiment results of manipulator's bending range and bending characteristics indicated that the manipulator could meet the requirements of transoral surgery. The variable-stiffness experiments showed that the manipulator could achieve a stiffness variation ratio up to 84.07 folds. Laryngeal phantom experiments and ex vivo tissue experiments were performed to further demonstrate the feasibility of the proposed manipulator. We believe this study could provide new ideas for the development of flexible manipulators requiring high load capability.