Degree Type

Thesis

Date of Award

2011

Degree Name

Master of Science

Department

Mechanical Engineering

First Advisor

Pal A. Molian

Abstract

Drug eluting stents have made significant advances in reducing restenosis over bare metal stents; however, further research is required to decrease the likelihood of late stent thrombosis. Thrombosis is often caused by hypersensitivity to the stent, the polymer, and the drug. This study investigates the potential to eliminate the polymer on drug eluting stents to decrease the chance of the requirement of a second procedure to reopen the artery. Nanosecond laser texturing of metallic stent surfaces generates laser-induced periodic surface structures, also referred to as ripples, which can be utilized to promote drug adherence directly to the stent surface. Surface profilometer results demonstrated that laser texturing significantly improves surface topography over bare metal stents. With a 488% increase in volume per unit area, laser texturing dramatically increased the volume of drug that can be contained in the valleys of the stent surface. In addition, the mean valley slope was improved by 420%, indicating that the aspect ratio of the valleys is significantly higher resulting in a higher resistance to erosion of the drug by the flow of blood during stent placement. Drug elution trials proved that laser texturing of metallic stents offers steadier release rates and better drug adhesion than biodegradable polymer stents. Since drug elution tests are expensive to carry out to determine conditions that will yield the desired release rate, an analysis is made using the weighted property index method and the following surface characteristics: surface area ratio, surface roughness, volume of lubricant per unit area from the bearing ratio analysis, and mean valley slope. This study compared four speeds ranging from 0.5 to 1.25 mm/s and showed that 1.25 mm/s produced the greatest ripple formation while minimizing process time.

DOI

https://doi.org/10.31274/etd-180810-2751

Copyright Owner

Michelle Kay Buehler

Language

en

Date Available

2012-04-30

File Format

application/pdf

File Size

72 pages

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