Steerable Tip Enables Expanding Robot to Pass Sigmoid Curve

Colonoscopy is a powerful tool for the early detection of colorectal diseases. State-of-the-art colonoscopy, yet effective, often elicits discomfort among individuals, deterring some from undergoing this crucial diagnostic procedure. In addition, advancing the colonoscope up to the ileocecal valve demands a high level of expertise of the physician. The length of the colon requires the colonoscope to have a certain bending stiffness to resist buckling and looping during insertion, leading to substantial contact forces exerted on the colon wall. This contributes to patient discomfort and the risk of injuries or perforations of the colon. The general de- mand for increased patient-safety and simplified medical interventions, motivates the investigation of alternative approaches for the examination of the colon [1]. Expanding, Growing or Everting Robots are soft contin- uum robots whose locomotion principle is based on the eversion of a tubular vessel [2]. Locomotion is achieved by the growth of the robot at its tip, whereby the lumen of the robot is pressurized with gas while the robot’s base is fixed. No relative motion between robot body and the surrounding occurs, avoiding friction-related issues. The soft body of the robot can be shaped by its en- vironment, without compromising the ability to expand at the tip. These attributes recommend its application for colonoscopy. The lack of relative movement between robot and colon wall is expected to reduce intraoperative pain. Due to expansion at the tip, no counteractive forces are applied to the colon along the robot body. Furthermore, the working principle allows a design as a resource-efficient single-use device ensuring sterility. Similar approaches are described by Manoj et al. and Pore et al. [3], [4]. Manoj et al. use a motorized head unit to perform growth and retraction, while Pore et al. placed the actuation components in the robot base in a pressurized chamber. A soft robot for colonoscopy, whose growth is described as longitudinal expansion of a latex tube, stored in the robot’s tip, is described in [5]. The ColonoSight system addresses similar is- sues, however the working principle differs from the locomotion described above [6]. The application of expanding locomotion in colonoscopy rises challenges regarding maneuverability, the integration of camera and working channels, and the prevention of buckling during retraction. Aim of this work is to enable systematic investigation of the factors influencing the locomotion, such as ge- ometry and material of the tubular vessel as well as control strategies of gas pressure in combination with advancement/retraction speed. Focus is on a safe and reproducible locomotion of an expanding robot in the colon. A modular setup is described, that allows for simple testing of parameter configurations. In addition, a preliminary validation of the test rig design is described using a simplified course resembling the colons anatomy.