Date of Award

Spring 2004

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering - (M.S.)

Department

Biomedical Engineering

First Advisor

Michael Jaffe

Second Advisor

Treena Livingston Arinzeh

Third Advisor

George Collins

Abstract

This study evaluated the effect of extrusion process variable on mechanical properties of extruded collagen tubes made using a specialized extruder, made by ZOKO Corporation of Czechoslovakia. Three extrusion variables were considered; extrusion speed, linear draw rate and rotation speed. Using Taguchi L4 matrix, a design of experiment (DOE) was run. Two mechanical properties, wall thickness and estimated elastic modulus, were considered as response of this DOE. Data was analyzed statically to evaluate the effect of extrusion variables on both these properties. Result of this study showed that linear draw rate of the extrusion process has the highest influence on wall thickness and rotation speed has highest influence on elastic modulus.

Additional studies evaluated effects of post-extrusion treatment on properties of the tubes. Collagen is a biodegradable material so it degrades very fast in the body. A proposed use of these tubes is as vascular grafts. To serve this purpose the tubes have to be treated to degrade slowly in the body so that when it degrades newly formed vessel replace it. Studies were performed to compare two different cross-linking methods, coagulation methods and cross-linking time for a glutaraldehyde crosslinking process. Two crosslinking methods, considered in this study, are crosslinking by glutaraldehyde and EDC/NIHS. Result of these studies showed that, crosslinking with glutaraldehyde gives higher degree of crosslinking than EDC/NHS; and the coagulation with acetone and ammonium hydroxide is also more effective than coagulation with just ammonium hydroxide solution. Crosslinking time study for glutaraldehyde showed that increase in degree of crosslinking after 15 minutes is very slow.

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