I. Bioanalytical applications of polymer microfluidic devices. II. Examination of soft vibrational modes for alkanes adsorbed on copper

Part I. The use of poly(dimethylsiloxane) (PDMS) in the construction of microfluidic devices was explored. PDMS devices, fabricated using soft lithographic techniques were used in electrophoretic separations and patterning processes The native polymer surface has a more complicated effect on electroosmotic flow, and studies of microchip designs to account for drift in separations were completed. Because of PDMS's low surface energy, the modification of the surface with metals is difficult. An adhesion procedure was developed to allow for metallic patterns to be embedded in the surface. The use of these metal patterns in electrochemical detection of electrophoretic separations were explored. PDMS also has shown to be useful in the fabrication of surface patterns. A method was developed that allows for the fabrication of protein gradients using depletion in the fluid flow of the device. Studies of the biological implications of the patterning process were undertaken to understand how spatial constraints presented by the patterns affect the growth and behavior of cultured neurons. Taken together, these studies provide several examples of the multiple uses for PDMS microfluidic devices and the impacts they have in a variety of bioanalytical areas.; Part II. The study of saturated hydrocarbons on metal surfaces continue to be of interest in order to understand molecule-surface interactions related to C-H bond activation. Interest has also been enhanced by the presence of a unique spectral feature, a broad vibrational mode that is shifted to lower frequency from the normal C-H stretching region. This work explores the appearance and location of this soft mode in non-reactive systems by examining the vibrational spectra of cyclic and linear alkanes on Cu(111). Careful comparisons to theoretical calculations and use of isotope labeled molecules allow us to categorize the soft mode feature as one that originates from the methylene symmetric C-H stretch. The appearance of the soft mode is dependent on the molecule to surface distance and the strength of charge-transfer from the metal to the adsorbate. These studies provide a clearer interpretation regarding spectroscopic features and their significance as it relates to hydrocarbon-metal interactions.