Bibliographic record
Abstract
The work presented in this thesis focuses on the study of viscous and elastic polymer thin films in initially unstable configurations. The systems are driven to flow viscously or deform elastically to minimize their free energy. Since these experiments take place on length scales at which gravity does not play a role, the physics is governed purely by surface tension and viscosity in the case of fluid films, or elasticity in the case of rigid films. It is also possible to combine hydrodynamics and elasticity, for example, a viscous film that flows in response to the bending energy of an elastic perturbation, or an elastic film deformed by the capillarity or flow of a fluid. Viscous flow in thin polymer films is studied in a system which is free-standing in air, meaning it has two fluid-air interfaces. Cylindrical holes are formed part way through a nano-scale polymer film, creating an unstable geometry with dissimilar surface areas at the two interfaces. When heated above its glass transition temperature, surface tension drives the film to flow to minimize its total excess surface area. The evolution is first dominated by fast vertical flow, which equilibrates Laplace pressure through the film by forming symmetric holes at each interface. Slow horizontal flow then becomes dominant, which continually reduces excess surface area by filling in the holes. A novel atomic force microscopy method is developed to monitor the two interfaces of a film as they flow, allowing the total free energy evolution of the system to be measured. The results agree with a hydrodynamic model developed to describe both stages of flow. Elastic instabilities, where a rigid film deforms in response to geometrical confinement, are studied in a free-standing bilayer system consisting of a thin film on a pre-strained elastic substrate. These instabilities include sinusoidal wrinkling of the capping film, or, since the entire bilayer is free-standing, global buckling, where the entire system deforms out-of-plane. The transition between wrinkling and buckling is found to depend on the thickness and moduli ratios of the films, as well as the pre-strain in the substrate. A simple model shows good agreement with experiments. Finally, the interaction between elasticity and viscosity is studied by measuring the flow of a viscous fluid perturbation driven by the bending energy of a rigid capping film. The experimental scaling of the perturbation size is in agreement with the theoretical prediction in the large perturbation limit.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".