Dynamic analysis of a soft capsule robot self-propelling in the small intestine via finite element method

Abstract

To reduce potential trauma to the intestine caused by the rigid shell while optimising its progression efficiency, an elastomer coating was applied to a self-propelled capsule robot for small-bowel endoscopy. The robot is self-propelled by its periodically excited inner mass interacting with the main body of the capsule in the presence of intestinal resistance. This work explored the dynamic responses of the capsule with different elastomer coatings (with different elastic moduli and thicknesses) in the lumen of the small intestine through a three-dimensional finite element analysis. The driving parameters of the robot, including the amplitude, frequency and duty cycle of the square-wave excitation, were further tested to reveal the dynamics of this soft robot. By analysing the numerical results, the proposed finite element model can provide quantitative predictions on the contact pressure, resistance force and robot-intestine dynamics under different elastomer coatings. It was found that the softer the elastomer coating is, the less contact pressure between the robot and the intestine is, so leading to less traumas. The findings of this work can provide design guidelines and an evaluation means for the robotic engineers who are developing soft medical robots for bowel examinations as well as the clinical practitioners working on capsule endoscopy.