Mechanical & Materials Engineering, Department of


Date of this Version



A Thesis Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering, Under the Supervision of Professor Carl A. Nelson. Lincoln, Nebraska: May, 2012

Copyright 2012 Jeff Midday


Natural Orifice Translumenal Endoscopic Surgery (NOTES) is a relatively new surgical approach which uses no external incisions, thereby improving cosmetic outcomes, decreasing overall recovery time and reducing the risk of external infection. In standard NOTES, flexible endoscopic tools have been used to carry out a variety of surgical procedures in the abdomen. As an alternative, miniature in vivo robots can be fully inserted into the peritoneal cavity and utilized to perform various surgical procedures. These in vivo robots eliminate tool triangulation issues, improve multi-tasking capabilities and greatly increase freedom and dexterity when compared to standard endoscopic and laparoscopic tools. One major limitation is that once inserted, the in vivo robots are isolated within the abdomen and cannot send or receive materials to the external environment. The focus of this thesis is a Material Handling System (MHS) that has been developed to bridge this deficiency.

This system features a flexible silicone overtube and an open-loop control system with manual and automatic operation capabilities. The system utilizes the helix of a spring to advance a payload along the length of the overtube. All of the design rationale, design decisions, components and materials are discussed. Additional description of all of the electronic hardware, coupled with the programming logic, provides detailed insight into the open-loop control strategy. The bench-top and in vivo testing results of the completed device are presented.

This thesis also addresses finite element modeling of the dimensional changes of silicone tubing under bending. The model looks at the complex issue of modeling a continuum rubber such as silicone, validated experimentally. The model provides general guidelines for the bending and kinking properties of a wide variety of tubing diameters and thicknesses. This tubing model can increase an engineer’s ability to properly dimension and tolerance an overtube, such as that found in the MHS, based on the bending criteria of the device.