Preliminary Friction Force Measurements on Small Bowel Lumen When Eliminating Sled Edge Effects

Frictional resistance model for tissue-capsule endoscope sliding contact in the gastrointestinal tract

“…It is assumed that neodymium magnets are used in a PillCam Colon capsule and that they consume 15% of the capsule volume. Using the density of neodymium ( ), and the volume ( ) and mass ( ) of the PillCam Colon 2, the weight of the magnetic capsule can be calculated using equation (28).…”

“…Others have extensively studied the effect of capsule diameter, length, speed, normal force, and velocity, all of which were studied to assess model validity in this work. In summary, literature reports that resistance force is directly proportional to capsule speed [21][22][23][24][25][26][27][28][29], diameter [20-24, 29, 30], length [23,29,30], and normal force [21,23,31].…”

Macro-Scale Tread Patterns for Traction in the Intestine

“…The intestinal mucus is a shear-thinning fluid so the apparent viscosity decreases with increasing shear rate [47]. While static, the tacky mucus provides an adhesive force and then, during shear, resistance comes from the viscosity of the mucus which opposes shear force [47][48][49].…”

“…This interaction of the tread with the tissue is also discussed in [44]. Due to the viscoelastic properties of the tissue, velocity will have a significant effect on this resistance as is dependent on the modulus of the tissue and high shear rates result in a higher modulus [29,39,48,49].…”

“…This may explain the high friction coefficient at low normal loads for the micro-scale treads in Table 1, as the coefficient is calculated by dividing the resistance ( ) by the normal load and mucus properties are not dependent on load (as indicated by [53] and [30]). The lack of direct contact means that the maximum traction -and indeed tractive effort -will be limited by the rheological properties of the mucus [49] and controlling traction using normal load would be largely ineffective; This is highlighted by the fact that the friction coefficients of the microscale patterns mentioned in Table 1 were seen to reduce by 43 -80% [14,40,42] with an increase in normal load. This effect may be worsened by mucus being progressively squeezed out of the tissue, enhancing lubrication [43,48] and likely further preventing real contact with the tissue substrate.…”