Structure-Function Integration in Snake-Bone Based on Honeycomb Pattern and Thermoplastic Polymer for Endoscopic Procedure

Abstract

In robot-assisted endoscopic procedure, snake-bone located at distal part of the endoscope is required to flexibly bend for adjusting tip position and passing through the body's winding anatomical pathways. After reaching the target lesion, it should serve as a stable platform to support precise operations. Therefore, it is necessary to develop a snake-bone with both bending and stiffness adjustment capabilities. To address these challenges, this paper proposes a novel snake-bone based on a bioinspired honeycomb pattern and the thermoplastic polymer polycaprolactone (PCL), which achieves structure-function integration. Compared with conventional endoscopic snake-bones, our snake-bone in a rigid state has a greater loading capacity, withstanding a torque of 293 Nmm while providing a maximum bending stiffness of 97,297 Nmm2. In a flexible state, the snake-bone exhibits an excellent 2 degrees-of-freedom (DOF) bending motion performance, with a maximum bending angle of 90 deg. This snake-bone can switch states within 18.37 s (from rigid state to flexible state) and 18.65 s (from flexible state to rigid state). Different from other material-based variable-stiffness snake-bones, our snake-bone incorporates an active cooling mechanism. Moreover, compared with other variable-stiffness snake-bones, our snake-bone can achieve variable stiffness while maintaining a reasonable outer diameter. Through phantom experiments, the snake-bone can support surgical instruments in performing endoscopic tasks, facilitating stable operations. The experimental results have proven the feasibility of the snake-bone, highlighting its significant potential for application in endoscopic procedures.