Bioinspired Design of a Soft Self-Propelling Radially Expanding Mechanism for Flexible Colonoscopes

Abstract

Background: Currently colonoscopies are difficult procedures to complete without complications. Due to the limitations in the state of the art flexible colonoscopes specialized maneuvers are required in order to allow the colonoscope to travel into the colon and reduce colon stretching. This thesis proposes a novel self-propelling mechanism designed to enhance the current flexible colonoscopes allowing for a better completion rate and fewer complications in colonoscopies. Methods: First an analysis was made of the fundamental types of propulsion and how well they could be used for locomotion inside the human colon. In order to determine the conditions the design has to meet a list of requirements was made. A wide variety of concepts were considered, which were then reduced to the three most promising concepts. These concepts were further developed and out of these, the most promising design was chosen. This design was adjusted in order to create a proof-of-principle prototype which was used to validate the design and give new insights into the type of self-propulsion used. Results: The prototype is able to perform locomotion in all tested tube/instrument diameter combinations, including tubes with a significant larger diameter than the instrument. Furthermore, the prototype is also able to perform well in tubes with an irregular shape and with a conical shape, both with and without lubrication. The effect of added weight to the tubes was also investigated and showed no significant effect. The efficiency of the prototype, as determined by the slip ratio, showed no significant variation during these tests. Discussion and Conclusion: The proof-of-principle experiments demonstrated that the design is capable of performing locomotion in the tested scenarios with better than expected efficiency. The lack of significant variation of slip ratio in tubes with a larger diameter than the prototype itself were unexpected and could significantly change the design of future iterations of the instrument. The issues which came up during the experiment gave new insights into the working of this type of locomotion which were used to make recommendations for future iterations of the design and recommendations for further tests, which could be performed to investigate unexplained results. The current design meets all the requirements set out for it and gave valuable new insights which will be useful for future iterations of the design making it a good first step towards developing a better colonoscope.