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Title: Study of the rheology of thin liquid films : novel flexible molds for nanoimprinting
Author: Barbero, David
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2011
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This thesis is composed of two parts: the first one is devoted to the rheology of thin liquid polymer films, the second one deals with the development of novel exible stamps for imprinting of micro- and nano-structures. Thin films are ubiquitous, and they are used in a large number of technological applications. An understanding of their properties, and of the factors influencing their stability is therefore important. In particular, the rheological properties of thin liquid films, and the role played by interactions at the solid/liquid interface have been subject to much debate in recent years. In this thesis, a new experimental set-up was built to study the destabilization process of a thin liquid polymer film subject to an electric field. The measurement of the characteristic time of destabilization of thin liquid films of polystyrene on a solid substrate provides a way to measure the viscosity of the liquid layer. I also extended the use of multiple beam interferometry to the measure of thickness fluctuations in the thin film due to an electrohydrodynamic instability only a few microns wide. This method allows the measurement of the growth rate of an instability with sub-nanometer resolution, and gives complementary information about the hydrodynamics of the liquid film. The results of this work lead us to propose a model for the disentanglement of large macromolecules during the formation of the thin film by spin-coating. The low density of entanglements in spin-cast films provides an explanation for the higher mobility observed in thin liquid layers. The last part of the thesis deals with the development of a new type of flexible organic molds for nanoimprinting. I show that patterning of polymer surfaces can be performed with high resolution (~10 nm) and at relatively low cost using these new molds. They also solve a number a problems often encountered with conventional inorganic materials which makes them easier to use and better suited to pattern large areas. I finally demonstrate applications of these molds to build a stretchable laser, and to manufacture thin transparent microstructured surfaces to study insect adhesion.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral