Colonoscopy is a standard medical procedure in which a long and flexible endoscope is inserted into the rectum for inspection of the large intestine and for simple interventions. Pushing the endoscope tip from behind via a long and flexible tube leads easily to buckling when the tip comes in contact with sharp curves in the intestinal wall. Buckling is accompanied by painful cramps and makes it difficult to complete the procedure. A way to avoid buckling is not to push the tip from behind, but to use the friction with the intestinal wall to pull the tip forward. This paper describes the state-of-the-art in research on intestinal locomotion methods and presents a new locomotion method based on a rolling donut that is positioned around the endoscope tip. The donut functions like a circular caterpillar and is constructed from three stents that generate high friction with the intestinal wall. The diameter of the donut can be changed and the stents can be driven independently to reduce slip in intestinal curves. The resulting Rolling-Stent Endoscope contains a new steerable mechanism by which the tip can be bent in all directions over a very large angle. The Rolling-Stent Endoscope was applied for a patent and a prototype is under development for evaluation in the intestine of a pig.

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