Date of Award

Spring 1-21-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Ronald Pak

Second Advisor

Franck J. Vernerey

Third Advisor

Bengt Fonberg

Abstract

Due to their biological relevance, lipid coated vesicles, such as liposomes, microbubbles or microdroplets are used in many areas of medicine such as targeted drug delivery or ultrasound imaging. Hence, a deep knowledge of the mechanics of those vesicles will provide a better understanding on many processes, aid in the design of new drugs or improve the imaging quality among others.

A vesicle can usually be described as an enclosed fluid body where its interface with the outer environment consists of lipid molecules which are generally assembled in single or double layers. Within those layers, lipids are in constant motion and, from a continuum point of view, the interface can be idealized as a compressible viscous fluid-like film constrained to a two dimensional manifold, which is embedded in a three dimensional space. The stretchability comes from the fact that the spacing between lipids can be increased, or reduced, and the inertial forces are disregarded due to the small length scale of the lipids.

This fluid model of the film behavior is a result of several studies at the molecular level that were able to successfully describe many processes present on a lipid coating, such as phase separation, transport or diffusion, through the individual motion of lipid molecules. Thanks to that, we can use a continuum theory for the mechanics of a fluid coating and describe how this activity on the interface affects the overall behavior of the vesicle. To that end, the object of the project is to develop a multiscale, numerical model of a lipid coated vesicle where its response to external inputs accounts for small scale mechanics of its fluid interface. The model will use a meshfree particle method that will provide a highly accurate description of the membrane while being able to handle large deformations without the hindering steps of creating a mesh or refining it.

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