Date of Award

Spring 1-1-2012

Document Type


Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

Mark Rentschler

Second Advisor

Virginia Ferguson

Third Advisor

Jeffrey Luftig


To optimize the design of a robotic capsule endoscope (RCE) capable of exploring and delivering targeted medical therapy to the gastrointestinal tract, it is necessary to quantify the mechanical properties of the aforementioned environment. This research aims to empirically determine a coefficient of friction (COF) between the small bowel lumen and several potential RCE materials and to study how the friction response varies with velocity and contact area along the length of the bowel, specifically when eliminating edge effects from the testing coupon (sled).

To obtain friction force measurements, a novel tribometer was designed and experiments were conducted to measure the friction on the small bowel lumen surface as a function of sled speed, material, contact area, presence of a leading edge and in situ versus in vitro conditions. The friction forces ranged from 0.001 N to 0.06 N under these conditions. A dry friction model was used to extract a COF from the measured forces and COF values ranged from 0.0004 to 0.05. The results show that the COF increases with increasing sled velocity. Contact between polydimethylsiloxane (PDMS) and the intestinal lumen yields a larger COF than that of stainless steel or polycarbonate. The COF does not demonstrate significant changes with pressure, but does respond to changes in contact area and weight, although the complexities of that relationship were not thoroughly investigated in this research. The results also indicate that by eliminating edge effects, the friction force between a stainless steel sled and the small bowel lumen surface is decreased. The average COF for in situ testing was found to be slightly lower than in vitro tests. These results can be incorporated into the design and control of an RCE to improve mobility within the gastrointestinal tract.