The atomic force microscope (AFM) was used to study a series of self-assembled systems: alkanethiol self-assembled monolayer (SAM), diblock copolymer thin film, solid supported lipid bilayer membrane, and microgel with double interpenetrating polymer network.
In the first system, packing and restructuring of self-assembled monolayers as exhibited by several alkanethiol systems (1-hexanethiol, 1-decanethiol, 11-ferrocenyl-1-undecanethiol) is demonstrated using conducting probe AFM (CP-AFM). Pressure is induced by an AFM tip, and simultaneously, electrical behavior is measured via detection of tunneling currents between metallic tip and substrate. The behavior is fit using a mechanical model that attempts to predict the observed junction resistance as a function of applied force with consideration for mechanical restructuring of the monolayer at higher loads.
CP-AFM is also used to study self-assembled thin film of the diblock copolymer polystyrene- block-polyferrocenylsilane (PS-b-PFS) on gold substrate. Simultaneous height and electrical current imaging verify the phase separation of the two blocks of the polymer and additionally, distinguish each block due to differential conductivity.
The phase separation of multi-component phospholipid bilayers (phosphatidylcholine/ sphingomyelin/ cholesterol) on supporting substrate into liquid-ordered and liquid-disordered phases is demonstrated using both topographical imaging, and the use of force map analysis through tip indentation and rupture measurements. The segregation and differential mechanical stiffness of the phases help to understand the important role of mechanical stability and rigidity membranes. An automated batch analysis process was implemented to facilitate the procedure.
The mechanical properties of microfluidically produced microgels (cross-linked sodium alginate and poly(N-isopropylacrylamide)) are measured using indentation experiments, to evaluate the suitability of these gels as cell-mimics. Nanoscale heterogeneities were avoided by using a tipless cantilever. This body of work shows that the alginate content of these microgels can be varied to tune their mechanical properties and that a platform for mechanical measurement of cell and cell-mimics is possible.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/26286 |
| Date | 18 February 2011 |
| Creators | Li, James K. |
| Contributors | Walker, Gilbert C. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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