Tailored Surfaces: Modifying Chemical and Physical Properties at the Liquid/Solid Interface to Address Optimizing Surface Chemistry Applications

Abstract

The research presented in this PhD thesis focuses on surface modification techniques to enhance potentially useful behavior of materials on surfaces. The principal objectives of this work include (1) investigating the physico-chemical phenomena at the liquid⁄substrate interface to enhance current methods of moving meso- scale liquid droplets (2) developing a polymer brush gradient on silicon to enhance the efficiency in binding and detection of probe molecules and (3) tailoring a poled substrate by electrostatically binding polar molecules to form a molecular assembly. Research was conducted by varying the physical properties of a liquid in motion (including, surface tension, viscosity) and the characteristics of the substrate upon which the liquid moves. The latter will include both physical and "chemical" roughness (i.e., variation of chemical functionalities present at the surface unit) of the substrate.

We also identified an efficient method of increasing DNA immobilization and hybridization. A polymer brush molecular weight gradient was used as a platform for DNA attachment. Fluorescence microscopy was used to obtain relative fluorescence intensity values indicating DNA hybridization and attachment to the polymer backbone. The microscopy technique provided evidence indicating an increase in DNA attachment to the polymer backbone as the polymer chain length increased.

A method of using self-assembly to develop interactions between a polarized ferroelectric domain and polar molecules was also studied. We demonstrated selective binding of bromoacetic acid to a single faced poled lithium niobate surface using XPS. Thus, a poled substrate was tailored by electrostatically binding polar molecules to form a molecular assembly.