Experimental investigation of frictional and viscoelastic properties of intestine for microendoscope application

Abstract

The information on the frictional resistance of a self-propelled robotic capsule endoscope moving inside the body is very important for the design and the performance enhancement of such parameters of the capsule endoscope as power consumption, motion control and positioning accuracy. Based on this motivation, the ultimate goal of this research was to develop an analytical model that can predict the frictional resistance of the capsule endoscope moving inside the living body. In this work, experimental investigations of the fundamental frictional characteristics and the viscoelastic behaviors of the small intestine were performed by using custom-built testers and various capsule dummies. The small intestine of a pig was used for the experiments. Experimental results showed that the average frictional force was 10-50 mN and higher moving speed of the capsule dummy resulted in larger frictional resistance of the capsule. In addition, the friction coefficient did not change significantly with respect to the apparent area of contact between the capsule dummy and the intestine, and also the friction coefficients decreased with an increase in the normal load and varied from 0.08 to 0.2. Such frictional behaviors could be explained by the lubrication characteristics of the intestine surface and typical viscoelastic characteristics of the small intestine material. Also, based on the experimental results, a viscoelasticity model for the stress relaxation of the small intestine could be derived.KEY WORDS: biotribology, capsule endoscope, small intestine, stress relaxation, viscoelasticity Nomenclature F Friction force (N) l Friction coefficient N Normal force applied to the capsule (N) r(t) Stress applied to the small intestine (Pa, N/m 2 ) 0Strain applied to the small intestine t Time

Modeling of Velocity-dependent Frictional Resistance of a Capsule Robot Inside an Intestine

“…Then, the group found that the variation of resistance was correlated with the viscoelasticity of the intestine. A five-element model is used to describe the viscoelastic property of the intestinal stress relaxation [13]. Furthermore, the group first developed an analytical model for the frictional resistance prediction, which was verified by finite element analyses [14].…”

Analytical Friction Model of the Capsule Robot in the Small Intestine

“…Furthermore, the velocity of CR was proved to affect the friction resistance when CR moves in the intestine. Kim et al [24] obtained a qualitative result that the friction goes up with the velocity increasing by experiment. My previous work also shows the same result [25,26,27], and we analyzed the friction resistance of CR at stage of start, stop and uniform motion [28].…”

Modeling of Frictional Resistance of a Capsule Robot Moving in the Intestine at a Constant Velocity

“…The characteristics of the capsule, such as weight, shape, dimension, material, contour line and surface preparation methods also have great influence on the friction. Researches show that the friction of smooth cylindrical capsule is smaller than other shapes [17,18]; the influence of the capsule's length on the friction is greater than that of the diameter [19]; capsule's quality has no significant effect on the friction [20]; and resin material is suitable for making capsule's shell [21]. Much less attention has been paid to the effect of capsule robot's motion parameter such as velocity and acceleration on the frictional resistance.…”

“…Much less attention has been paid to the effect of capsule robot's motion parameter such as velocity and acceleration on the frictional resistance. The relation between the friction and the velocity of the capsule has been analyzed qualitatively [17,19]. The result shows that the friction goes up with the velocity increasing.…”