Development of an Esophageal Sleeve with Variable Stiffness and Internal Diameter for Endoscopic Surgery

In natural orifice transluminal endoscopic surgery, the flexible endoscopic surgical robot utilizes a continuum configuration to navigate narrow, multi-curvature esophageal pathways. However, the tool channel's dimensional limitations and the restricted internal layout make it challenging to reduce the outside diameter and highly efficient variable stiffness function significantly. As a result, safe insertion into the esophagus and precise operation remains hugely challenging. In this paper, an esophageal sleeve with variable stiffness and internal diameter is developed for endoscopic procedures. The proposed esophageal sleeve adopts specially designed spiral elastic deployable parts that allow for variations in internal diameter. Furthermore, the elastic deployable parts are designed with serrated protrusion structures that can realize rapid transition between rigidity and flexibility under negative pressure. Fundamental experimental results showed that the outer diameter of the proposed esophageal sleeve can expand from 17 mm to 20 mm, providing inner access up to 13 mm for endoscopic instruments. The serrated protrusion structure allows the esophageal sleeve to rapidly transition from a flexible to a rigid state, resulting in a stiffness gain of approximately 5. Phantom experiments validated the effectiveness and usability of the proposed Esophageal sleeve in assisting endoscope insertion, demonstrating its potential clinical value in endoscopic procedures.