Modeling and experimental investigation of rotational resistance of a spiral-type robotic capsule inside a real intestine

In this study, the rotational resistance of a spiral-type capsule rotating inside a small intestine is investigated by in vitro experiments and analytical modeling, on which a limited literature is available. The results presented exhibit viscoelastic nature of the intestinal tissue. The significance of various spiral structures and rotating speeds is quantitatively evaluated from the propulsion point of view. Also, an analytical torque model is proposed and subsequently validated. The close match between the experimental results and numerical results from the model shows that the model is reasonably accurate to estimate the rotational resistance torque of the small intestine. Both the experimental and modeling works provide a useful guide to determine the torque required for a spiral-type endoscopic capsule operating in a 'really' small intestine. Therefore, the proposed torque model can be used in the design and optimization of in-body robotic systems, which can remotely be articulated using magnetic actuation.