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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Physics

Year Degree Awarded

2016

Month Degree Awarded

May

First Advisor

V. Adrian Parsegian

Second Advisor

Rudolf Podgornik

Subject Categories

Atomic, Molecular and Optical Physics | Biochemistry, Biophysics, and Structural Biology | Biological and Chemical Physics | Condensed Matter Physics | Materials Science and Engineering | Nanoscience and Nanotechnology | Polymer and Organic Materials | Quantum Physics | Statistical, Nonlinear, and Soft Matter Physics

Abstract

Van der Waals (vdW) interactions influence a variety of mesoscale phenomena, such as surface adhesion, friction, and colloid stability, and play increasingly important roles as science seeks to design systems on increasingly smaller length scales. Using the full Lifshitz continuum formulation, this thesis investigates the effects of system materials, shapes, and configurations and presents open-source software to accurately calculate vdW interactions.

In the Lifshitz formulation, the microscopic composition of a material is represented by its bulk dielectric response. Small changes in a dielectric response can result in substantial variations in the strength of vdW interactions. However, the relationship between these changes is complicated and often over-simplified in popular approaches. Three example systems are used to study the effects of material modifications, to characterize important system parameters, and to elucidate this commonly misunderstood relationship. Modification of example dielectric spectra at a particular frequency influences all terms in the Matsubara summation of the Hamaker coefficient. The terms most affected by the change are distributed doubly non-locally over all frequencies and not confined to terms near to modification. Thus, the possibility of eliminating vdW interactions by spectral variation at a narrow frequency range is very remote.

Orientational dependence of vdW interactions is generally attributed to the effects of anisotropies of body shapes and dielectric responses. In order to disentangle these effects, the angular dependencies for several systems displaying a range of anisotropies are examined and the effects of shape and material anisotropies are mutually isolated in detailed calculations. Shape anisotropy effects are shown to result in torques between arrays of cylinders that are surprisingly stronger than those between half-spaces, even for arrays constructed of isotropic material.

Full Lifshitz's calculations of vdW interactions, though complicated and lengthy, accurately capture important effects in mesoscale systems. The Gecko Hamaker open-science software and its accompanying open database of optical properties provide users with the accurate vdW calculations that are necessary for deliberate mesoscale design and construction. The Lifshitz formulation gives Gecko Hamaker the unique capability to address orientational degrees of freedom, allowing users to calculate torques and angular-dependencies. The large variety of calculations made possible by Gecko Hamaker provides insights into mesoscale interactions that were previously inaccessible to users, such as DNA-DNA interaction's dependence on base pair composition and the unusual non-monotonic interactions displayed by certain single-walled carbon nanotubes. This dissertation includes previously published coauthored material.

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