Bacteria in nature predominantly grow as biofilms on living and non-living surfaces. The development of biofilms on non-living surfaces is significantly affected by the surface micro/nano topography. The main goal of this dissertation is to study the interaction between microorganisms and nanopatterned surfaces. In order to engineer the surface with well-defined and repeatable nanoscale structures, a new, versatile and scalable nanofabrication method, termed Spun-Wrapped Aligned Nanofiber lithography (SWAN lithography) was developed. This technique enables high throughput fabrication of micro/nano-scale structures on planar and highly non-planar 3D objects with lateral feature size ranging from sub-50 nm to a few microns, which is difficult to achieve by any other method at present. This nanolithography technique was then utilized to fabricate nanostructured electrode surfaces to investigate the role of surface nanostructure size (i.e. 115 nm and 300 nm high) in current production of microbial fuel cells (MFCs). Through comparing the S. oneidensis attachment density and current density (normalized by surface area), we demonstrated the effect of the surface feature size which is independent of the effect on the surface area. In order to better understand the mechanism of microorganism adhesion on nanostructured surfaces, we developed a biophysical model that calculates the total energy of adhered cells as a function of nanostructure size and spacing. Using this model, we predict the attachment density trend for Candida albicans on nanofiber-textured surfaces. The model can be applied at the population level to design surface nanostructures that reduce cell attachment on medical catheters. The biophysical model was also utilized to study the motion of a single Candida albicans yeast cell and to identify the optimal attachment location on nanofiber coated surfaces, thus leading to a better understanding of the cell-substrate interaction upon attachment. / Ph. D. / Formation of surface associated multicellular communities of microorganisms known as biofilms is of concern in medical settings as well as in industries such as oil refineries and marine engineering. It has been shown that micro/nanoscale surface features can highly regulate the process of biofilm formation and the attached cell activities. In this dissertation, we study the interaction between surface nanoscale structures and bacterial adhesion by experiments and biophysical modelling. We develop the Spun-Wrapped Aligned Nanofiber (SWAN) lithography, a versatile, scalable, and high throughput technique for masterless nanopatterning of hard materials. Using this technique, we demonstrate high fidelity whole surface single step nanopatterning of bulk and thin film surfaces of regularly and irregularly shaped 3D objects. SWAN lithography is used to texturize the electrode surface of microbial fuel cells (MFCs), which are envisioned as an alternative sustainable energy source. Compared to the non-patterned electrodes, the electrodes with 115 nm surface patterns facilitate larger biofilm coverage and 40% higher current production. We also develop a biophysical model to optimally texturize the surface of central venous and uretic medical catheters to prevent biofilm formation by fungal pathogen, Candida albicans. We show that the surface structures that result the highest cell total energy retained the least C. albicans. Furthermore, the adhesion behaviour of a single yeast cell is also experimentally studied in conjunction with the developed model.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/85387 |
| Date | 24 April 2017 |
| Creators | Ye, Zhou |
| Contributors | Mechanical Engineering, Behkam, Bahareh, Ellis, Michael W., von Spakovsky, Michael R., Nain, Amrinder, Mukhopadhyay, Biswarup |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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