Portland State University. Department of Physics
Andres La Rosa
Date of Publication
Master of Science (M.S.) in Physics
Near-field microscopy -- Evaluation, Acoustic microscopy, Mesoscopic phenomena (Physics), Viscoelasticity
1 online resource (xi, 113 pages)
The recently developed Shear-Force Acoustic Near-Field Microscope (SANM) is used to investigate the viscoelastic properties of a mesoscopic fluid layer confined between two trapping boundaries, one being a stationary substrate and the other the apex of a laterally oscillating tapered probe. Hardware improvements and evaluation of the SANM-probe robustness will be a major focus of this thesis. The investigation first discusses characterization and recent developments made to the microscope, including: modifications to the sensor head, conditioning of the Nano positioners electrical drive signal, and the assessment of the probe against eventual plastic deformation or compliance against interactions with samples (the latter comprising a solid substrate and its adhered fluid layer which is typically a few monolayers thick). Furthermore, this study includes an analysis of the adsorbed mesoscopic fluid's viscoelastic properties. This inquiry aims to better understand probe-sample interactions with the mesoscopic fluid. This includes adhesion, wetting, and to inquire the nature of the hydrophobic interaction, which is relevant in many areas of study such a protein folding, and interfacial friction which has wide ranging applications including desalination. This analysis will be performed using a Sheer force microscopy (implemented with quartz tuning fork QTF), and another recently introduced technique Whispering Gallery Acoustic Sensor (WGAS). The latter allows more direct monitoring of the QTF's mechanical displacement. These measurements will be supplemented by simultaneously monitoring the acoustic emission from the mesoscopic fluid under confinement between the probe and the substrate, which will be monitored using the SANM sensor positioned beneath the substrate.
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Brockman, Theodore Alex, "Shear-Force Acoustic Near-Field Microscopy and Its Implementation in the Study of Confined Mesoscopic Fluids" (2018). Dissertations and Theses. Paper 4710.