Experimental Study Concerning the Effects of Profile Morphology of Intestine on the Frictional Characteristics

This work is supposed to determine how intestine morphology influence the intestine friction. Rabbit duodenum was acted as the research object. We characterized inner structure of small intestine, tested the mucus lubricity and measured the change relationships between radial strain, load, sliding velocity and friction coefficient in condition of removing the normal pressure. The results show that inner surface of small intestine mainly included plicas, villi and microvilli. The mucus can reduce the friction coefficient to 10^-2 magnitude. Hoop strain 10% was the critical point of friction coefficient shifting. That is to say, when hoop strain was less than 10%, load and sliding velocity had no influence on the friction coefficient, but while hoop strain was more than 10%, the friction coefficient increased as load and sliding velocity increased. At last, we analyzed the relationships between the friction coefficient and radial strain, inner morphology, mucus, load and sliding velocity, thus friction mechanism was concluded. When the hoop strain was less than 10%, plicas were bended to form wrinkles which were capable to store mucus, the lubrication regime was 1iquid lubrication. When the hoop strain was more than 10%，the plicas were stretched and the wrinkles disappeared，the lubrication regime then was mixed lubrication. The study of its friction characteristics provides experimental data for the appearance design of capsule endoscopy and intestinal robot；besides，it is significant to promote minimally invasive and noninvasive surgery.