B.S. Chemical Engineering, University of California-Berkeley, 2007
Bacteria form biofilms when they are under nutrition deficient conditions or are exposed to antibiotic
environment, and these biofilms, once formed, would shield the bacteria from outside environment to
sustain their continual growth. The formation of biofilm is thus involved in various pathogenesis
depending on the type of bacteria shielded. Therefore, it is desirable to study the chemical composition
as well as the mechanical behavior of the biofilm in order to know this process and discover ways to
prevent the biofilm formation. In this project, the dynamic biofilm formation process is monitored by
continual measurement of the surface modulus, and the biofilm surface was observed using a Brewster
Angle Microscope to match the corresponding modulus measurement. The performance of several
proposed biofilm inhibitors were used; the mechanical properties of the biofilm were tested as well.
Oriented Single-Walled Carbon Nanotubes using Interfacial Flow Processing
Anisotropic single-walled carbon nanotubes (SWNT) possess electrical properties attractive to the fabrication of microelectronic devices. In this study, conjugated polymer coated SWNTs are aligned at the air/water interface with the use of a Langmuir trough and the orientation is observed with linear dichroism. The aligned SWNTs are then transferred to a substrate and the morphology observed using an electron microscope. Transitions from gaseous to liquid-expanded then to liquid-condensed phases of SWNTs are observed during compression of the monolayers, and SWNTs are aligned perpendicular to the Langmuir trough barrier direction when compressed to the liquid-condensed phase. At high compression rates, the flow induced anisotropy is more stable due to increased relaxation times of the SWNTs. The Langmuir trough method is successful in achieving SWNT anisotropy and the long orientational relaxation times of the nanotubes allow convenient transfer onto solid substrates. Film resistance measurements suggested optimal SWNT-to-polymer blend ratio and compression conditions result in enhanced electron conductivity. On the other hand, film resistance can also be significantly lowered by the preparation with multiple dipping.