Publication Date

Summer 2019

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Sang-Joon J. Lee

Keywords

Animal models, Arterial stiffening, Fatigue cycling, Multiphoton microscopy, Nicotine, Soft tissue mechanics

Subject Areas

Mechanical engineering

Abstract

Nicotine is an addictive substance found in electronic cigarettes (e-cigarettes) and cigarettes, and the use of such products has growing concern because of the prevalent use by young adults. Nicotine exposure degrades arterial tissue and results in increased arterial stiffness, which is linked to cardiovascular events, such as stroke and myocardial infarction. The hypothesis of this research is that fatigue loading reveals changes to the mechanical behavior of nicotine-treated arteries that is more informatively discriminating than stiffness alone. Ten murine arteries, five untreated and five nicotine-treated, were subjected to cyclic fatigue loading in an open-circumferential configuration by a custom tensometer with a motorized actuator and inline load cell. The specimens were subjected to an alternating strain of ±50%, superimposed on a mean strain of 150%. A power law was fit to the experimental data to extract parameters indicative of peak stress, loss of tension, degradation slope, and oscillation band. Compared to untreated specimens, nicotine-treated specimens exhibited a 108% higher peak stress, 118% greater loss of tension, and 107% larger width of the oscillation band. The tension loss and oscillation band width provided additional discriminating evidence of different mechanical behavior, supporting the hypothesis that fatigue testing can reveal distinctions in mechanical behavior that are not evident in static testing alone.

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