An investigation into biomechanical and biotribological properties of a real intestine for design of a spiral-type robotic capsule

This paper reports on the results and implications of our experimental investigation into the biomechanical and biotribological properties of a real intestine for the optimal design of a spiral-type robotic capsule. Experiments were conducted to measure the stress relaxation and the stress-strain relations, which indicate that the small intestine shows the typical behavior of a viscoelastic material. Within a certain range of strain, the intestine tissue appears to have a quasi-linear viscoelasticity. The strain ranges change when different strain rates are applied. Both strain and frequency affect the storage modulus of the intestine in dynamic shear tests. The sliding friction experiments were conducted with different bar-shaped solid samples to determine their sliding friction on the inner surface of the small intestine, which mimics the sliding friction between a spiral-type robotic capsule operating in an intestine. The results show that the viscoelastic materials cause higher coefficient of friction (COF) than the contacting objects made of other substance such as metal. Moreover, carving grooves on the contacting surface also increases COF. All these findings help to enhance the traction force of a spiral-type capsule by optimizing its topology.